ACNP 64^th Annual Meeting: Panels, Mini-Panels and Study Groups

January 12–15, 2026

Nassau, Bahamas

Sponsorship Statement: Publication of this supplement is sponsored by the ACNP. All content was reviewed and selected by the Program Committee, which held full responsibility for the abstract selections. Only Disclosures for presenting authors are listed. Individual contributor Disclosures may be found within the abstracts.

Panel

1. Lingering Temptations: Translational Neuroscience of the Incubation of Craving

1.1 Reducing incubated drug craving by reversing synaptic plasticity: a translationally relevant approach

Marina Wolf

Oregon Health and Science University, Portland, Oregon, United States

Background: We showed that incubated cocaine (Coc) or methamphetamine (Meth) craving in rats depends on persistent strengthening of glutamate synapses in nucleus accumbens (NAc) medium spiny neurons (MSN) via insertion of high conductance Ca2+ -permeable AMPARs (CP-AMPARs). I will present new data showing this mechanism generalizes to oxycodone (Oxy) incubation and addressing cell type specificity (D1 vs A2a/D2 MSN). For Coc, we showed that CP-AMPAR elevation depends on abstinence-dependent sustained activation of retinoic acid (RA) signaling via its dendritic receptor RARα, a druggable target. Our goal is to determine if this generalizes across drug classes and if our results can be replicated using more bioavailable RARα antagonists in development as therapeutics for other indications.

Methods: Male and female D1- or A2a-Cre rats (crossed with reporter lines) self-administer Sal, Coc, Meth or Oxy 6 h/d x 10d. After abstinence periods sufficient for incubation, whole cell patch clamp recordings assess AMPAR transmission in D1 or A2a/D2 MSN of NAc core. The main measure is the rectification index (RI), which increases as CP-AMPARs increase. We determine if interrupting RA signaling in slices reverses CP-AMPAR elevation and if interrupting RA signaling in vivo normalizes incubated craving. See Results for typical sample sizes.

Results: 1) After Meth incubation, the RI increased in D1 (p < 0.001 vs Sal) but not A2a MSN; after Oxy incubation, the RI increased for D1 and A2a MSN (p < 0.01) (18–43 cells/7–13 rats/grp).

2) Our published Coc data (2025) show that RA-mediated CP-AMPAR elevation is normalized by a RA synthesis inhibitor or commercially available RARα antagonist (e.g., p < 0.0001 for synthesis inhibitor) (11–18 cells/5–6 rats/grp). We are determining if the same applies to Meth and Oxy incubation.

3) For Coc incubation, we are determining if CP-AMPAR plasticity is normalized by new RARα antagonists in development for other indications. If so, these drugs will be tested for reversal of incubated cue-induced drug seeking (10–12 rats/grp).

Conclusions: We have identified a type of plasticity (CP-AMPAR elevation) important for both psychostimulant and opioid incubation. We are investigating whether the underlying mechanism identified for Coc (RARα signaling) also generalizes across drug classes, which is significant because RARα is a druggable target.

Disclosure: Nothing to disclose.

1.2 An animal model of incubation of craving after voluntary abstinence: behavior and circuits

Abstract Not Included

1.3 Neurophysiological markers in incubation of craving

Tifei Yuan

Shanghai Mental Health Center, Shanghai Jiaotong University School of Medicine, Shanghai, China

Background: Incubation of craving is central to methamphetamine use disorder (MUD) and both characterizes the disease and predicts relapse. However, there is currently a lack of robust and reliable biomarkers for monitoring craving and the incubation dynamics.

Methods: Here, we seek to identify a neurobiological signature of incubation for craving based on individual-level functional connectivity pattern differences between healthy control and MUD subjects. We train high-density electroencephalography (EEG)-based models using data recorded during the resting state and then calculate imaginary coherence features between the band-limited time series across different brain regions of interest.

Results: Our prediction model demonstrates that mPFC sourced the beta oscillation that contributes to incubation of craving, together with OFC. Beta functional connectivity networks have significant predictive value for craving at the individual level and can also identify individuals with MUD. Targeting mPFC beta oscillation reduces craving for methamphetamine.

Conclusions: These findings advance the neurobiological understanding in incubation of craving through an EEG-tailored computational model of the brain connectome. Dissecting neurophysiological features provides a clinical avenue for personalized treatment of MUD.

Disclosure: Nothing to disclose.

1.4 Incubation of cue-reactivity in cocaine and methamphetamine use disorders: evidence from EEG/ERP biomarkers

Muhammad Parvaz

Icahn School of Medicine at Mount Sinai, New York, New York, United States

Background: The phenomenon of incubation of craving—an increase in cue-induced drug-seeking behavior during abstinence—is well characterized in animal models but remains understudied in humans. Given that cue-reactivity is a well-established predictor of relapse, understanding its temporal dynamics during early abstinence has direct clinical relevance. We used the late positive potential (LPP), an event-related potential elicited by drug-related cues, to examine incubation of cue-reactivity in individuals with stimulant use disorders.

Methods: Study 1 assessed 48 individuals with cocaine use disorder (CUD) (mean age: 47.56 years, 12 females) at approximately 1 and 3 months of abstinence. Participants completed an EEG cue-reactivity task featuring cocaine and neutral stimuli. Study 2 involved 42 individuals with methamphetamine use disorder (MUD) (mean age: 36.18 years, 3 females), categorized into short- (mean = 25 days) and long-term (mean = 109 days) abstinence groups, using methamphetamine-related stimuli. LPP amplitude and underlying source activity were compared across timepoints and groups, and correlated with self-reported craving. Data analyses were conducted using paired t-test (Study 1) and independent sample t-test (Study 2), and Spearman correlation (Studies 1 and 2).

Results: In Study 1, LPP amplitude to cocaine cues increased significantly from 1 to 3 months (t = 3.37, p = 0.02), indicating within-subject incubation of cue-reactivity. In Study 2, individuals with longer abstinence exhibited significantly greater LPP amplitude to methamphetamine cues compared to those with shorter abstinence (t = 2.89, p = 0.032). In CUD, LPP amplitude was significantly greater in individuals with long- compared to short-term abstinence from methamphetamine use (t = 2.89, p = .032). Source localization implicated the caudal anterior cingulate cortex and precuneus underpinning the incubation of cue-reactivity in CUD and MUD.

Conclusions: These findings demonstrate that EEG-derived LPP is a promising biomarker of incubated cue-reactivity and suggest convergent neural mechanisms across stimulant use disorders. Ongoing analyses include the examination of brain networks, especially at a much finer time scale, to better delineate neural underpinnings of incubation of cue-reactivity in humans with stimulant use disorders.

Disclosure: Nothing to disclose.

Study Group

2. Artificial Intelligence in Mental Health: Bridging Innovation, and Clinical Translation

Martin Paulus, Carolyn Rodriquez, John Torous, Roy Perlis, Karthik Sarma, Olusola Ajilore, Sahib Khalsa

Laureate Institute for Brain Research, Tulsa, Oklahoma, United States

Study Group Summary: Artificial intelligence now touches every layer of neuropsychopharmacology. Diffusion models predict ligand-receptor affinities in silico, multimodal graph networks fuse fMRI, EEG, and rodent calcium movies to expose circuit motifs of anhedonia, and large-language models (LLMs) draft notes, flag relapse risk, and personalize self-report. Yet these prototypes remain stranded in the “validation-to-implementation gap”: few have reproducible biological grounding, audited fairness, or workflows that strengthen—rather than strain—the therapeutic alliance. To confront that impasse, this study group will bring together seven participants whose careers collectively span molecule-to-market translation and real-world implementation. Chair Martin Paulus (Laureate Institute) will frame the cross-scale problem: how do we move from AI-guided assessments of electronic health records to pragmatic outcomes? Co-chair Carolyn Rodriguez (Stanford) will outline translational trial designs and the FDA’s emerging “predetermined-change” pathways for adaptive algorithms. John Torous (Harvard/BIDMC) will bring empirical data on LLM-driven digital phenotyping and measurement-based care, while Roy Perlis (MGH) will discuss evidence requirements for AI systems for clinical trials and EHR-biobank analytics. Karthik Sarma (UCSF) will demonstrate how federated learning, electronic medical record integration, real-time workflow tools, and other informatics approaches can integrate new scientific insights into patient care, and Olusola Ajilore (UIC) will explore explainability thresholds for multimodal neuroimaging models, and Sahib Khalsa (UCLA) will possible AI-driven surrogate endpoints. In addition, key discussion threads will include the impact of AI on reshaping workforce capacity, with predictive rostering, no-show risk scoring, and real-time Patient Reported Outcomes-based triage that reduces wait-times. Second, multimodal patient assessment—wearables, speech biomarkers, and foundation models that fuse text-voice-video—promises continuous phenotyping and earlier relapse detection, while gradient-boost and LLM risk engines are cutting suicide attempts and inappropriate care escalation by double-digit percentages. Third, we will discuss equity and bias safeguards: federated learning on under-represented cohorts, natural language processing audits that flag disparate wait times, and counterfactual fairness dashboards. Fourth, we will emphasize that AI is driving administrative and research efficiencies, for example, ambient scribes have made thousands of clinician days available, auto-screeners now can profoundly reduce screening labor, and large language model handoff notes are viewed as “safe or safer” than human drafts, together recapturing millions in return on investment.

Disclosure: Nothing to disclose.

Panel

3. Stress Neurocircuitry and Transcriptional Mechanisms of Alcohol Seeking

3.1 Substance P innervation to the nucleus accumbens mediates alcohol consumption following chronic social stress

Jesse Schank

University of Georgia, Athens, Georgia, United States

Background: Social defeat stress (SDS) is a rodent model used to assess the effect of chronic stress on depressive-like behavior and alcohol intake. Our previous studies have indicated that the neurokinin-1 receptor (NK1R) mediates the behavioral responses to SDS, in part through its actions in the nucleus accumbens (NAC). The NK1R is the high affinity, endogenous target of the neuropeptide substance P (SP), and has been shown by our group and others to mediate alcohol seeking, anxiety, and stress responses.

Methods: We first infused a cre-dependent, retrogradely transported virus into the NAC of Tac1-cre mice (n = 6; Tac1 is gene for SP) to identify regions that send SP+ inputs to the NAC. We found that significant SP projections originated in the paraventricular nucleus of the thalamus (PVT). Next, we infused this same tracing strategy, exposed mice to SDS or control conditions, and assessed Fos expression in the PVT. We then manipulated the SP innervation to the NAC by infusing cre-dependent retro-AAVs in the NAC of Tac1-cre mice that drove the expression of either inhibitory or excitatory DREADDs.

Results: We detected increased Fos expression in NAC-projecting SP neurons of the PVT in SDS exposed mice relative to unstressed controls (n = 8, t14 = 2.2, p = 0.04). To manipulate SP innervation of the NAC, we infused a cre-dependent, retro-AAV that expressed and inhibitory DREADD receptor into the NAC of Tac1-cre mice (n = 9–14) and injected the DREADD actuator CNO (3 mg/kg, ip) prior to each defeat exposure. We found that CNO had no effect on SDS-induced social avoidance, which was expressed in all SDS exposed groups (F3,40 = 15.9, p < 0.001). However, CNO treatment reduced alcohol consumption (p = 0.008). In a following experiment, CNO was administered to inhibitory DREADD expressing mice (n = 12) prior to behavioral testing, as opposed to during stress. In line with the previous experiment, inhibition affected post-stress drinking (t11 = 2.7, p = 0.02), but not social behavior (t10 = 0.51, p = 0.62). Conversely, chemogenetic activation of these inputs in stress-naïve mice acutely increased alcohol intake (n = 13–15, t27 = 3.4, p = 0.002) without affecting social behavior (t26 = 1.4, p = 0.18).

Conclusions: Together, these results suggest that SP innervation of the NAC, likely from the PVT, mediates alcohol consumption following stress.

Disclosure: Nothing to disclose.

3.2 Cell type-specific signatures of social stress-escalated alcohol consumption in the paraventricular thalamus

Rajani Maiya

Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States

Background: Repeated exposure to social stress can lead to escalated alcohol consumption in humans and animals. The biological underpinnings of this are not clear and must be elucidated to facilitate identification of therapeutic targets. Using a system for activity-dependent genetic tagging and a mouse model for social defeat stress (SDS)-induced escalation of alcohol consumption, we have identified a role for a discrete population of paraventricular thalamus (PVT) neurons in regulating SDS-escalated alcohol intake in both sexes.

Methods: Male (N = 34/group) and female (N = 16/group) mice underwent 10 sessions of SDS followed by 24-hour intermittent alcohol access procedure. Mice were sacrificed 90 minutes after the last SDS session for cFos immunohistochemistry (N = 4/group). Fos-TRAP mice (Fos-2A-Cre; Ai14) were used to genetically label SDS-activated PVT neurons and track their activity during subsequent alcohol exposure (N = 4–6/group). Chemogenetics was employed to inhibit SDS-activated neurons during alcohol intake (N = 10 male, 6 female mice/group). Single-nuclei RNA sequencing (snRNASeq) was performed on 45,000 nuclei from PVT tissue (3 samples from 6 mice).

Results: SDS led to robust and persistent escalation of alcohol intake (p < 0.0001 males and p = 0.001 females) and preference (p < 0.0001 in males and p = 0.018 in females). SDS increased cFos expression in the PVT (p < 0.0001). Both SDS and subsequent alcohol exposure activated largely overlapping (~80% overlap) PVT neurons (cFos, p = 0.0045; tdTomato, p = 0.0027). Chemogenetic inhibition of SDS-activated neurons in the PVT attenuated alcohol intake in both sexes (p = 0.03). snRNASeq revealed five transcriptionally distinct PVT neuronal subtypes (PVT1-5), with the PVT2 cluster containing the highest proportion of stress- and alcohol-activated cells. Of 151 differentially expressed genes, 139 were restricted to stress and alcohol co-activated neurons, with strong enrichment in TGFβ-related pathways.

Conclusions: Our data identify a molecularly distinct, stress- and alcohol-responsive neuronal population in the PVT that regulates SDS-escalated alcohol intake. The overrepresentation of TGFβ-signaling genes in these neurons suggests a novel targetable mechanism for comorbid stress and alcohol use disorders.

Disclosure: Nothing to disclose.

3.3 Long-term effects of adolescent social exclusion on vulnerability to alcohol and stress-related disorders in rats

Esi Domi

University of Camerino, Camerino, Italy

Background: Social exclusion perceived during adolescence in the context of modern lifestyles si rapidly escalating and has emerged as a significant contributor in psychiatric disorders. Adolescents are commonly exposed to bullying and social exclusion, experiences that can often elicit Fear of Missing Out (FoMO). Within this framework, we implemented a novel “FoMO” rat model of social exclusion to investigate its’ long-term impact on alcohol- and stress-related disorders in adulthood.

Methods: Male and female Wistar rats (N = 10/20 per group) were subjected to social exclusion from postnatal day 21 (PND21) to PND60, a developmental window paralleling early-to-late adolescence in humans. To quantify FoMO-related behaviors, a deep learning-based classifier capable of quantitively assessing social performance was implemented. In adulthood, alcohol- and stress-related behaviors were assessed using the operant alcohol self-administration and the cued fear conditioning paradigm. We used c-Fos mapping as a proxy of neuronal activation to identify the brain regions associated to social exclusion.

Results: DeepLabCut analysis achieved a root mean squared error of 8.33 pixels, indicating reliable behavioral tracking. In adulthood analysis of alcohol-related behavior demonstrated sex-specific effects of adolescent social exclusion (SE). SE females administered a significantly higher number of alcohol rewards compared to the control group (p < 0.01). In stress-induced relapse to alcohol seeking, contrary to females, SE males failed to show shock-induced relapse. In the fear conditioning paradigm, SE males exhibited increased fear expression while SE females showed increased fear conditioning compared to the interaction control group (p < 0.05). Additionally, SE females but not males showed blunted corticosterone response compared to the control group. Preliminary results of neuronal activation among multiple brain regions showed a specific and a significant decrease in c-Fos activity in the basolateral amygdala (BLA) of male SE rats compared to social interaction controls (p < 0.01).

Conclusions: Out findings demonstrate sex-specific long-term effects of adolescent social exclusion on alcohol and stress-related behaviors and these effects might rely on neuronal adaptations within the BLA neurocircuitry.

Disclosure: Nothing to disclose.

3.4 Single nucleus RNA sequencing reveals Fgf-R1 in central amygdala as a candidate treatment target for compulsive alcohol use

Markus Heilig

Linköping University, Linköping, Sweden

Background: Continued use of alcohol despite negative consequences, a.k.a. “compulsivity”, is a key symptom of alcohol use disorder. Using punishment resistant alcohol self-administration in rats as a reverse-translational model of compulsivity, we recently identified PKCdelta+ neurons in centrolateral amygdala (CeL) as a neural substrate of this behavior (Domi et al. Science Adv 2021). Here, we searched for the underlyiing molecular mechanisms.

Methods: Male and female rats (n = 64/sex) were characterized for compulsivity. Parallell groups were yoked, as control for shock exposure alone. Extremes of high vs. low compulsivity, and yoked controls were processessed for for snRNAseq of individual CeA (n = 12/group, for a total of 72).

Sequencing was as described (Dilly et al. Transl. Psychiat 2022). Weighted Gene Co-Expression Network Analysis (WGCNA; Langfelder and Horvath BMC Bioinform 2008), was applied to GABA-ergic cells. This identified modules that showed consistent differential expression (compulsive vs non-compulsive, as well as compulsive vs footshock yoked).

PKCdelta:Cre rats (Toivanen, Petrella et al, J Neurosci 2024), and a Cre-depedendent shRNA AAV5 vector were used for cell-type specific knock-down (KD).

Results: The top differentially expressed module mapped to PKCdelta neurons (p < 0.0001), with Fgf-R1 having the highest loading on the module eigengene. The pattern of differential expression in females was different, in agreement with our recent behavioral findings (Toivainen et al, Biol Sex Differ 2024). Initial validation studies therefore focused on males, RNAscope in situ confirmed overexpresson of Fgf-R1 in CeL of compulsive rats (n = 7/group; p = 0.02), and selectively in PKCdelta neurons (p = 0.005). Compulsive rats from a batch of PKCdelta: Cre rats (batch size: n = 64) were injected into the CeL with a Cre-dependent Fgf-R1 KD (n = 7) or a control vector (n = 8), and allowed 3 weeks for vector expression. Compulsive self-administration rates were suppressed in the KD vector group (response rates: p < 0.05; resistance score: p < 0.01).

Conclusions: Up-regulated Fgf-R1 expression in PKCdelta+ CeL neurons is a causal factor behind compulsive alcohol self-administration. The FDA approved Fgf-R1 inhibitor inigratinib is brain penetrant (Rajendran at al, Br J Pharmacol 2023), It can be used to translate our findings into humans.

Disclosure: Indivior, Grant, Self, Indivior, Honoraria, Self, Janssen, Other Financial or Material Support, Self, Brainsway, Advisory Board, Self

Panel

4. How Brain Estrogen Levels, Receptors and Signaling Govern Behaviors Across Sexes: Genes, Circuits, Synapses

4.1 Ovarian hormones in brain plasticity and disease risk: insights from multiomic single-cell approaches

Marija Kundakovic

Fordham University, Bronx, New York, United States

Background: Ovarian hormone fluctuations contribute to the increased prevalence of depression and anxiety disorders in women, although the underlying mechanisms are underexplored. To this end, we have shown that anxiety-related behaviors vary across the estrous cycle in mice, and we linked these changes to changes in chromatin and gene expression in the ventral hippocampus (vHIP), the area critical for emotion regulation.

Methods: To further address this question, here we characterized gene expression and chromatin accessibility in the mouse vHIP at single-cell resolution across sex and the estrous cycle, focusing on diestrus (low estradiol-high progesterone) and proestrus (high estradiol-low progesterone). >55,000 nuclei from 11-week-old diestrus and proestrus females and males (N = 6/group) were processed using the 10XChromium Single-Cell Multiome (ATAC+Gene-Expression) kit. We overexpressed transthyretin (Ttr) in excitatory neurons of the vHIP using AAV viruses, and performed open-field, elevated plus maze and forced swim tests (N = 10/group).

Results: We identified 60 cellular clusters in the vHIP, including subtypes of excitatory and inhibitory neurons, astrocytes, microglia, oligodendrocytes and endothelial cells. We found sex- and estrous cycle-dependent changes in cellular proportions among clusters, including dynamic changes in the dentate gyrus, critical for hippocampal neurogenesis. While the highest number of differentially expressed genes (DEGs) are found in excitatory neurons, we found extensive chromatin changes across cell types. Within cell subtypes, we identified DEGs and differentially accessible regions across the cycle and sex, including genes relevant for synapses, neurogenesis and behavior. We identified Ttr, encoding a thyroid hormone transporter, as an important sex- and hormone-dependent candidate gene. By overexpressing Ttr in excitatory vHIP neurons of female mice, we showed its functional relevance for anxiety- and depression-related behavioral changes across the estrous cycle.

Conclusions: We provide critical insights into sex--dependent gene regulation relevant for emotion regulation and neuroplasticity. This work informs the neurobiology underlying sex bias in depression and anxiety disorders, paving the way for precision medicine approaches taking sex and hormonal state into account.

Disclosure: Nothing to disclose.

4.2 Estradiol and epigenetic regulation shape age-dependent stress susceptibility across the lifespan

Polymnia Georgiou

University of Wisconsin Milwaukee, Milwaukee, Maryland, United States

Background: Fluctuations in gonadal hormones influence stress vulnerability across the lifespan. Adolescence is marked by a surge in estrogen, while aging is characterized by its decline. Despite these opposite directions, both periods are associated with increased risk for stress-related mood disturbances, though the underlying mechanisms remain unclear.

Methods: To investigate how estradiol modulates stress vulnerability, we used both sexes and a combination of systems neuroscience, bioinformatics, in vivo recordings, behavioral, and pharmacological approaches (n = 10–12).

Results: Decreased estradiol (E2) or ERβ signaling, mimicking aging, led to stress-induced reward impairments, mediated by the ERβ expressing basolateral amygdala to the nucleus accumbens pathway in males. Activating this ERβ-expressing pathway restored normal reward behavior under acute stress, while inhibition increased vulnerability. In females, ERβ agonists are prophylactic against stress-induced deficits, though ERβ deletion did not result in the same susceptibility observed in males. ERβ knockouts also exhibited impaired sleep, characterized by increased REM sleep during the day and elevated delta and gamma power following acute stress. During adolescence, but not adulthood, acute stress led to social deficits with no sex differences. RNAseq from human adolescent brain tissue with MDD showed downregulation of steroid biosynthesis pathways. Drug repurposing identified HDAC inhibitors as potential modulators of these differences. Further analysis showed HDAC4 upregulation and acetylation changes on histones 2B and 3. These findings suggest that decreased histone acetylation or increased HDAC activity may suppress steroid hormone synthesis during adolescence, increasing depression risk. To validate this, mice treated with the HDAC inhibitor TCA before stress showed reversal of adolescent social deficits and prevention of open-field deficits in adulthood.

Conclusions: In conclusion, our findings suggest that E2 and ERβ signaling play a critical role in stress resilience during aging, while stress-induced epigenetic suppression of steroid pathways heightens vulnerability during adolescence. Targeting ERβ circuits or HDAC activity may offer age-specific strategies for preventing stress-related disorders.

Disclosure: Nothing to disclose.

4.3 The surprising role of high hippocampal estrogen levels and sex-specific receptor signalling in PTSD-like memory disturbances induced by acute trauma

Rachael Hokenson

University of California, Irvine, Irvine, California, United States

Background: With increasing mass shootings and climate-driven natural disasters, it is becoming evident that acute traumatic events (ATS; consisting of physical, emotional and social stress) can provoke enduring disturbances of memory in up to 30% of those exposed. Memory disturbances can include generalization of trauma-related memory cues and can evolve to post-traumatic stress disorder (PTSD). PTSD, is twice as common in women even when controlling for trauma type. Why?

Methods: We probed in mice the fundamental sex differences underlying memory vulnerability to ATS, focusing on the role of estrogen (17β-estradiol) and its receptor (ER) signaling in hippocampus. We imposed ATS on males and on females during high (proestrus) or low (estrus) physiological estrogen levels. We measured hippocampal estrogen levels and manipulated them by blocking the hormone’s production. We blocked specific ERs pharmacologically, and used conditional knockout mice to delete hippocampal ERα or ERβ selectively.

Results: Surprisingly, high physiological hippocampal estrogen levels (41.8 ± 6.6 pg/g; proestrous females; 33.4 ± 5.5 pg/g, males; 19.9 ± 2.2 pg/g, estrous females) were required for ATS-induced memory loss and generalization of fear memories in both sexes: Object location memory was disrupted in male and proestrous female, but not estrous females (N = 7–16/group; 2-way ANOVA, Šidák’s multiple comparisons). ATS resulted in fear generalization in mice with high hippocampal estrogen levels: When pairing cues with ATS, male and proestrous female ATS mice avoided concordant and partial cues the following week but estrous female ATS mice did not (N = 10–18/group; Mixed-effects analysis, Dunnett’s). Reducing estrogen levels using letrozole rescued memory and prevented fear generalization. Pharmacological and transgenic approaches showed signaling via ERα in males and, in contrast, ERβ in females, as mechanisms for these memory problems.

Conclusions: While estrogen is required for memory, the role of optimal vs high levels in the effects of acute trauma on memory are more nuanced. Our data suggest high hormone levels facilitate ATS-related psychopathology, with an inverted U-type relation of estrogen levels and outcomes. Males and females use different ERs to mediate ATS-induced PTSD-like disturbances, pointing to potential targets for intervention.

Disclosure: Nothing to disclose.

4.4 Estrogen receptor α signaling modulates synaptic function in the nucleus accumbens

Tara LeGates

University of Maryland, Baltimore County, Baltimore, Maryland, United States

Background: Synaptic plasticity within the reward system plays a key role in regulating motivated behaviors. Estradiol (E2), widely known as a female gonadal sex hormone, can modulate synaptic function and motivated behaviors in both sexes, though relevant synapses and relationships between synaptic and behavioral effects remain unclear. Plasticity of hippocampus (Hc) - nucleus accumbens (NAc) synapses is a critical regulator of reward-related behaviors, particularly those related to spatial/contextual learning. We sought to determine whether E2-dependent signaling modulates Hc-NAc synapses and related behaviors.

Methods: D1-tdTomato or C57BL/6J mice (8–10 week old male and female) were used unless otherwise stated. To test roles for gonadally derived E2, ovariectomy (OVX) was performed at 6 weeks old +/− E2 replacement, and SHAM operated mice served as controls (n = 8 per group). We used whole-cell electrophysiology to record from medium spiny neurons (MSNs) in the NAc shell. To measure protein expression, Western blot analysis was performed on proteins extracted from NAc tissue (n = 5–8 per group). We used social interaction, novelty suppressed feeding, and conditioned place preference to evaluate motivated behaviors (n = 12–20 per group).

Results: We found that while the strength of Hipp-MSN synapses is similar between males and females, the mechanisms by which synaptic strength is regulated differs between the sexes. Specifically, long-term potentiation (LTP) in males requires NMDARs while LTP in females is NMDAR-independent and instead relies on L-type voltage gated Ca2+ channels (L-VGCCs) and requires ERα activity. ERα signaling modulates the function of L-VGCCs in both sexes and some of the observed E2 effects in females may be due, at least in part, to gonadal E2.

Conclusions: Our work provides important insight into sex-specific mechanisms by which E2 influences synaptic function critical for modulating motivated behaviors. We identify sex-similar roles for ERα in MSNs while latent sex differences may be the key factor underlying the involvement of ERα in behavior and plasticity in females. Identifying key factors involved in plasticity within the reward system advances our understanding of the neurobiological basis of motivated behaviors and offers potential targets for studying related disorders and developing therapeutic treatments.

Disclosure: Nothing to disclose.

Panel

5. Decoding Pain: Brain Structural and Functional Biomarkers

5.1 Brain morphometry and recovery of pain signatures following surgery for trigeminal neuralgia

Mojgan Hodaie

University Health Network, Toronto, Canada

Background: Trigeminal neuralgia (TN) is a debilitating neuropathic facial pain condition that can be effectively treated with surgery. Imaging-derived brain biomarkers for chronic pain have been limited, and predicting surgical response remains a challenge. Machine learning (ML) can aid in the identification of objective brain imaging biomarkers that comprise dynamic pain signatures to explain the neural underpinnings of TN. In this study, we investigated whether structural magnetic resonance imaging (MRI) metrics could aid in predicting surgical response.

Methods: MRI scans were obtained from 1068 healthy controls (HC) and 117 TN patients before and after pain-relieving surgery. All TN patients were age- and sex-matched with HC. FreeSurfer 7.0 was used to derive 259 whole-brain MRI metrics. Ensembles were optimized to detect pain signatures that differentiated HC from TN and were used for brain age prediction. All ensembles were validated on 100 local HC.

Results: A subcortical pain signature comprised of cognitive regions showed that 96/117 TN (82%) shifted towards a healthier brain phenotype after pain-relieving surgery (q < 0.001). Nonlinear data decomposition illustrated clustering of pre- and post-surgery TN and HC, suggesting that normalization is nonlinear in nature. The most important feature was the left accumbens area, with larger volumes being more predictive of a recovery from TN. A cortical thickness pain signature replicated these findings, where thicker gyri of the left occipito-temporal area and cuneus were most predictive of TN recovery. As all 117 patients responded to surgery, patients with more prominent pain signatures preceding surgery may be more responsive to surgical pain relief. TN patients showed a trend of accelerated brain aging compared to HC.

Conclusions: Our longitudinal study identified novel, reversible TN pain signatures that may help predict surgical response. We illustrated that brain structure alone is sufficient for ML to distinguish between TN and being pain-free, and that recovery from neuropathic pain may be detectable within a year of pain-relieving surgical intervention. These findings provide a foundation for mechanistic and ML-based studies of cortical and subcortical regions in TN, many of which are related to cognition, and support the potential for ML to augment clinicians.

Disclosure: Nothing to disclose.

5.2 Neuroimmune signatures of pain persistence in youth: a longitudinal multi-site biomarker study

Laura Simons

Stanford University, Palo Alto, California, United States

Background: Chronic musculoskeletal (MSK) pain during adolescence poses a substantial risk for lifelong disability, yet current treatments often fail to address early neurobiological risk factors. The SPRINT study—a multisite, prospective longitudinal cohort—was designed to identify prognostic signatures by integrating high-dimensional data.

Methods: Youth aged 11–18 years (N = 152; 85% female) presenting for treatment of musculoskeletal (MSK) pain at one of three tertiary pediatric pain clinics were enrolled. At baseline, participants underwent structural and functional MRI, quantitative sensory testing (QST), blood collection for immune profiling via mass cytometry (CyTOF), and completion of validated self-report measures assessing pain-related functioning. Clinical outcomes were assessed regularly from baseline to 12 months. Gradient-boosted decision trees (XGBoost) were applied to identify prognostic markers from multimodal data spanning neural, immune, and psychosocial domains. All models adjusted for age, sex, pain duration, and study site.

Results: Multimodal data spanning CyTOF (1,960 features), resting-state fMRI (1,431), multisensory fMRI (1,017), structural MRI (1,718), QST (23), and questionnaires (63) were analyzed to identify early predictors of pain outcomes at 12 months. A network-based visualization revealed strong intramodal clustering across feature types, indicating distinct but interrelated biological and psychosocial signatures. Late-fusion models demonstrated significant performance in predicting pain unpleasantness at 12 months. Among top predictive features were immune signatures—particularly memory regulatory T cells activated by LPS stimulation—associated with worsening pain unpleasantness trajectories, and structural MRI features such as decreased surface area, curvature, and folding index in the left medial premotor and dorsolateral prefrontal cortices (A8m, A9m). These neural features were negatively associated with pain unpleasantness at 12 months.

Conclusions: This study identified multimodal biomarker signatures that predict long-term pain outcomes—particularly those related to cortical structure and T cell profiles. These findings support the potential of integrative, systems-level modeling to inform precision treatment strategies.

Disclosure: Nothing to disclose.

5.3 Clinical pain increases with accelerated brain ageing, yet placebo effects are preserved

Luana Colloca

University of Maryland Baltimore, Baltimore, Maryland, United States

Background: Chronic pain is associated with accelerated brain aging, as estimated through neuroimaging biomarkers like brain-age difference (BAD), the gap between chronological and estimated brain age. It is unknown if the placebo effect, which some studies showed decreases with age, is associated with brain aging. We tested this question in participants with a primary diagnosis of temporomandibular disorders (TMD) and healthy controls (HC) in 2 cross-sectional studies.

Methods: Study 1 included 401 TMD participants and 400 pain-free HC participants. TMD participants first completed the Graded Chronic Pain Scale to measure orofacial pain severity and interference. Next, we assessed the placebo effect in all participants using a classical conditioning and verbal suggestion procedure. In Study 2, we used magnetic resonance imaging (MRI) to examine structural features associated with brain aging in 84 TMD participants from Study 1 and 84 sex- and age-matched HC participants from the Cambridge Centre for Ageing and Neuroscience database. A Gaussian process regression (GPR) model was used to estimated brain-age from cortical thickness measures.

Results: In Study 1, older chronological age was associated with worsening chronic pain severity. Older age was associated with greater pain interference before mid-to-late adulthood (47.9 years), but not later in life. There was a significant group-by-age interaction in influencing placebo hypoalgesia. Specifically, placebo hypoalgesia decreased with age in HC but not TMD participants. In Study 2, TMD participants showed older brain-age compared to HC. Older brain-age was associated with worsening pain severity, and brain-age statistically mediated the association between chronological age and pain severity. Estimated brain-age was not associated with or mediated placebo hypoalgesia in TMD participants. Results confirm prior evidence of accelerated brain aging in chronic pain and demonstrate that brain-age statistically mediates age-related increases in pain severity.

Conclusions: Age-related reductions in placebo hypoalgesia were observed in HC but not in TMD participants. Importantly, placebo hypoalgesia in TMD participants was not decreased despite accelerated brain aging highlighting distinct cognitive-affective pathways for non-pharmacological interventions in older adults.

Disclosure: Nothing to disclose.

5.4 In vivo examination of mGlu5 receptor in people with chronic pain

Irina Esterlis

Yale Translational Brain Imaging Program, New Haven, Connecticut, United States

Background: Chronic pain (CP) is a significant source of personal and public health burden but the lack of safe, effective, and widely available treatment for CP is a critical concern. Preclinical researchers have identified the upregulation in metabotropic glutamate receptor type 5 (mGlu5) as a consequence for the experience of pain and as a promising treatment target. Here, we examined the relationship between mGlu5 availability, pain, and CP in vivo in human for the first time.

Methods: One hundred and twelve individuals from a transdiagnostic sample [n = 42 healthy (HC), n = 38 major depressive disorder, n = 31 bipolar disorder; n = 57 no pain, n = 55 pain] completed comprehensive clinical, pain (BPI), and cognitive assessments and interviews, and participated in an [18F]FPEB positron emission tomography (PET) scan to measure mGlu5 availability. Volume of distribution (VT: equilibrium ratio of parent radioligand concentration in tissue relative to that in blood) was the PET outcome measure.

Results: There were no significant differences in demographic variables in the pain vs no pain groups. Two-way ANOVAs demonstrated a significant main effect of pain experience on mGlu5 availability. Negative correlations were observed between pain on the BPI and mGlu5 availability (r’s (29) = −0.41–0.47, p’s < .02). Additionally, VMPFC mGlu5 availability was negatively correlated with average pain levels (r(18) = −0.48, p = 0.04) and pain severity (r(18) = −0.48, p = 0.04). Finally, mGlu5 was negatively correlated with the perceived impact of pain on mood (r(18) = −0.52 to −0.60, p’s < 0.03). On cognitive tasks, mGlu5 was negatively correlated with errors on an executive control task and time on attention task (r’s −0.44–0.51, p’s < 0.01) in the no pain group (r’s −0.34–0.38, p’s < 0.04). In the pain group, mGlu5 availability was negatively correlated with errors on an executive control task (r(44) = −0.31, p = 0.04). Conversely, mGlu5 availability was positively correlated with reaction time on the task of attention (r’s 0.30–33, p’s < 0.04).

Conclusions: Contrary to preclinical findings in nonpsychiatric animals, we show lower mGlu5 availability in people with pain. Importantly, we observed that mGlu5 availability was associated with mood and cognitive symptoms in people with pain, suggesting this may be a treatment target to reduce the experience of pain.

Disclosure: Nothing to disclose.

Panel

6. Neuromodulation Underlying Social Deficiencies

6.1 MDMA restores cortico-accumbal signaling and rescues autism related social deficits

Jessica Walsh

University of North Carolina at Chapel Hill/School of Medicine, Chapel Hill, North Carolina, United States

Background: Autism spectrum disorder (ASD) involves social impairments from diverse causes, but shared symptoms suggest common mechanisms. Disrupted serotonin (5-HT) signaling and altered excitation/inhibition (E/I) balance are key hypotheses. We show a novel 2-dose MDMA regimen rescues social deficits across five ASD mouse models and restores E/I balance in the mPFC–NAc circuit, offering a promising circuit-based therapeutic strategy for ASD.

Methods: Male and female C57BL/6 mice and transgenic lines (Sert-Cre, 16p11.2flx/flx, Cntnap2-/-, Fmr1-/y,-/-, Arid1bflx) aged 8–20 weeks were used. VPA mice were made by injecting 600 mg/kg VPA or saline into pregnant C57BL/6 at E12.5. Controls were littermates or age-matched C57BL/6. Juvenile mice (3–5 weeks) were used in social assays. Mice had four test days: baseline, two MDMA doses (7.5 mg/kg, 48h apart), and a post-test. For sociability, time near juvenile vs. empty was measured. For optogenetics, AAV viruses were injected into mPFC or NAc, optic fibers implanted in NAc. Voltage clamp recorded mEPSCs, mIPSCs, and optically evoked EPSCs/IPSCs in NAc MSNs to assess E/I balance.

Results: A 2-dose MDMA regimen (7.5mg/kg, i.p.) causes long-lasting rescue of social deficits in five distinct ASD mouse models up to one week after the second dose. Rescue is independent of 5-HT1B receptor activation, as repeated 5-HT1B agonism failed and antagonism did not block MDMA's effect. Optogenetic activation of mPFC-to-NAc mimics the drug effect, while inhibition during MDMA blocks rescue, showing a bi-directional role. Synaptic changes likely underlie this effect in Sert-Cre+/−:Arid1bflx/+ mice.

Conclusions: This study shows that a short-term, 2-dose MDMA regimen sustainably reverses social deficits across diverse ASD mouse models, aligning with clinical trials where MDMA-assisted therapy reduced social anxiety in autistic adults for up to six months. The mPFC-to-NAc circuit is key to this effect in Sert-Cre +/−:Arid1bflx/+ mice. Optogenetic activation mimics MDMA’s effects, while inhibition during or after MDMA blocks rescue. Electrophysiology indicates presynaptic weakening, suggesting a target for therapies.

Disclosure: Nothing to disclose.

6.2 Elucidating mechanisms that provide sustained benefits for the rescue of social deficits: how social valence adjusts long-term social needs through top-down control of neuromodulation

Xiaoting Wu

Icahn School of Medicine At Mount Sinai, New York, New York, United States

Background: The ability to adjust social need dependent on the quality of social interactions is crucial for a healthy social life, but its underlying neural mechanism is unclear. Given there is no effective medication for sustained improvement of social deficits in autism spectrum disorder, achieving long-term regulation of prosocial behavior will likely be transformative for the development of new treatments. Our previous work suggests that the ventral (v) CA1 encodes social valence. Here, we will focus on the vCA1 to medial prefrontal cortex (mPFC) projection and its outputs to neuromodulation centers for the regulation of social homeostasis.

Methods: To manipulate the vCA1 to mPFC projection and mPFC outputs, optogenetic inhibition and excitation was applied during an initial social exposure. Mice were then subjected to sociability and social valence 3-chamber tests (n = 10–14, both sexes, 8–12 weeks old) without stimulation to assess learned sociability and valence or fiber photometry recordings (n = 5–6) to assess neuromodulator release. Moreover, subjects (n = 3–6 both sexes, 7–10 weeks old) underwent repeated valenced social interactions and acute slices were prepared 2 h later. A viral intersectional strategy was used to visualize mPFC neurons receiving inputs from the vCA1. Current-clamp recordings were performed from the fluorescently labelled neurons (n = 10–23) in experienced and naïve mice.

Results: We found that inhibition of the vCA1-mPFC projection ablates positive and negative social valence. Repeated valenced social experiences induced long-term excitability changes in mPFC neurons receiving inputs from the vCA1. Excitation of the vCA1-mPFC-dorsal raphe (DR) circuit enhanced sociability long-term (2 h after stimulation), whereas the activation of the vCA1-mPFC-pareventricular nucleus of the thalamus (PVT) circuit reduced sociability in a sustained manner. Excitation of the vCA1-mPFC projection increased both DR 5-HT and PVT neurotensin (NT) neuron activity.

Conclusions: Our results show that repeated valenced social experiences activate the vCA1-mPFC projection to induce differential neuromodulator release, which bi-directionally adjusts long-term social needs. These findings have broad therapeutic implications for treating long-term social deficits.

Disclosure: Nothing to disclose.

6.3 Effects of postpartum resource scarcity on maternal behavior and brain circuits

Debra Bangasser

Georgia State University, Atlanta, Georgia, United States

Background: In 2024, the U.S. Surgeon General highlighted a growing parental stress crisis, with poverty being a common stressor. Postpartum parents may be especially vulnerable to this stress due to heightened brain plasticity supporting nurturing and protective behaviors. However, little is known about how postpartum resource scarcity alters molecular signatures in brain circuits. Using a rat model of resource scarcity, limited bedding and nesting (LBN), we mimic aspects of poverty postpartum to study changes in nurturing, defense, and related circuits.

Methods: In LBN, rat dams and pups were housed with limited nesting material and no enrichment. Controls had ample resources. We assessed maternal care quantity and patterns. Poverty increases basolateral amygdala (BLA) activation to threat in humans postpartum, which can alter defensive behavior. In LBN, we tested defensive responses to an intruder. Ongoing long-read native RNA sequencing will examine gene, RNA isoform, and epitranscriptomic changes in the BLA of LBN vs. control dams.

Results: LBN dams increased pup-directed care (nursing, licking/grooming) at the expense of self-care (self-grooming, resting). Transition probability analysis revealed that, unlike control dams, LBN dams had unpredictable sequences of care. In response to an intruder, LBN dams attacked less than controls, with a striking reduction in pinning, a form of dominance. This pattern suggests that LBN dams find the intruder more threatening than control dams. These altered threat responses will be linked to gene, isoform, and epitranscriptomic differences in the BLA.

Conclusions: Postpartum brain plasticity supports infant care and defense, but resource scarcity alters these behaviors in this rat model. Identifying molecular signatures in the BLA may reveal targets for future interventions to promote adaptive maternal responses under stress. These findings provide a biological framework for understanding how socioeconomic hardship affects caregiving.

Disclosure: Nothing to disclose.

6.4 Accumbal calcium-permeable AMPA receptors mediate attachment

Zoe Donaldson

University of Colorado Boulder, Boulder, Colorado, United States

Background: The nucleus accumbens (NAc) is a central node in social attachment. Calcium-permeable AMPA receptors (CP-AMPARs), which are enriched on fast-spiking interneurons (FSIs) and mediate their excitation, are key regulators of accumbal circuit function. We investigated whether CP-AMPAR and FSI activity gate the formation of coordinated neuronal ensembles that encode partner-specific information in monogamous prairie voles.

Methods: Voles (n = 24, both sexes) received bilateral intra-NAc infusions of IEM-1460 or vehicle. We combined unilateral cannula-mediated pharmacology (IEM-1460) infusion prior to one-photon calcium imaging to monitor accumbal neuronal activity during social bonding (n = 15 animals, both sexes). Neuropixels 2.0 examined fast-spiking interneuron (FSI) activity and coordination with MSN ensembles.

Results: Bilateral CP-AMPAR blockade (IEM-1460) during cohabitation prevented partner preference formation (t(24) = 3.26, p = 0.003), despite normal mating and total social interaction.

CP-AMPAR inhibition disrupted temporally coordinated partner-encoding ensembles (mixed lm, treatment Β = −0.022, P = 0.015). CP-AMPAR blockade impaired across-day stability of partner neurons. while partner information remained decodable from overall neural activity (IEM-1460: T(6) = 2.11, P = 0.079), ensemble-based decoding failed (T(6) = 0.236, P = 0.821), indicating a specific loss of structured coactivity.

neuropixels recordings revealed that fast-spiking interneurons (fsis) exhibit monosynaptic inhibition of msns. bursts of fsi activity were tightly time-locked to msn ensemble activation, with significant deviation from shuffled controls.

together, these results show that CP-AMPARS are required for forming stable social preferences and organized neural representations of the partner, with effects likely mediated via interneuron coordination of MSN ensembles.

Conclusions: Our findings reveal a microcircuit mechanism in which CP-AMPARs and fast-spiking interneurons (FSIs) gate the formation of coordinated neuronal ensembles in the nucleus accumbens (NAc) that underlie pair bond formation. Social attachment depends on CP-AMPAR-mediated FSI control over ensemble dynamics, linking receptor-level plasticity to social attachment.

Disclosure: Nothing to disclose.

Panel

7. Human Neurodevelopmental Trajectories From Birth Through Adolescence and Risk for Psychiatric Disorders

7.1 Maternal childhood maltreatment and the newborn brain

Catherine Monk

Columbia University Vagelos College of Physicians and Surgeons, New York, New York, United States

Background: Childhood maltreatment affects 25% of the U.S. population and is associated with increased risk for psychopathology. Maternal history of childhood maltreatment is associated with greater infant resting-state functional connectivity (rsFC) between the amygdala and key regions of the prefrontal cortex (PFC) implicated in stress processing. Greater prenatal maternal depression is associated with similar alterations in infant amygdala-PFC rsFC. We hypothesized that maternal history of childhood maltreatment will be associated with greater amygdala-PFC rsFC, in regions involved in stress processing (vmPFC, ACC, dorsal-medial SFG, precentral gyrus), mediated by maternal mood.

Methods: This is a secondary analysis of an existing data set. N = 59 pregnant individuals, maternal age M = 36.3 years, 3rd trimester self-report of childhood maltreatment (CTQ), stress (PSS), depression (CES-D), pregnancy distress (PDQ), sleep problems (PSQI), pregnancy experiences (PES), and attachment insecurities (ECR), and infant fMRI at 2–7 weeks (N = 23/59 male). fMRI data were processed using the neoRS pipeline, and mean time series were extracted using the AAL atlas. We calculated the rsFC of amygdala with vmPFC, ACC, dorsal-medial SFG, and precentral gyrus using Pearson's correlation coefficients. We performed linear regression and mediation analyses. Bootstrapping with 1000 re-samplings was used to compute p-values.

Results: In mediation models, greater CTQ was associated with increased amygdala–dorsal SFG rsFC, mediated by PSQI (p = 0.036–0.042), and decreased amygdala–medial SFG rsFC, mediated by PDQ and ECR (p = 0.020–0.044). When stratified by sex, CTQ to amygdala to PreCG, dorsal and medial SFG rsFC associations were mediated by PDQ (p = 0.004–0.046). In females, CTQ to amygdala–medial and dorsal SFG rsFC associations were mediated by ECR and PSQI (p = 0.004–0.032).

Conclusions: Maternal history of childhood maltreatment is associated with increased newborn amygdala connectivity with regions implicated in spatial and self-referential processing and voluntary motor movements. Maternal pregnancy distress mediates these associations for males, and stress and sleep problems mediate these associations for females. Results suggest intergenerational transmission of maternal experience identified prior to parenting influences.

Disclosure: Nothing to disclose.

7.2 The developing visual system in autism: links to behavior, cognition, and genetic liability

Jessica Girault

University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States

Background: Evidence from neuroimaging studies of infants at familial (genetic) high likelihood (HL) for autism spectrum disorder (ASD) suggests that the visual system may develop atypically from infancy through school-age in ASD. Here we present new evidence from several lines of inquiry linking the atypical development of the visual system to indices of genetic liability, social behavior, and cognition from infancy through school-age.

Methods: Analyses utilize an overall sample of 385 (59% male) HL infants and a comparison sample of 107 (58% male) typically developing (TD) infants. MRIs were collected at 6, 12, and 24m of age, and at follow-up (ages 6–14yrs; n = 319). Diagnoses for ASD were made at 24m and/or follow-up (n = 89 ASD, 77% male). Linear models evaluated associations between visual system development and (1) social behavior and (2) visual-cognitive processing, adjusted for sex and age. Group-by-brain phenotype interactions tested for unique associations in ASD. Pearson correlations evaluated the strength of association between parental social behavior and infant brain development. We investigated white matter microstructure (fractional anisotropy; FA) in the splenium of the corpus callosum and surface area (SA) in primary and extrastriate visual cortex, guided by prior work.

Results: Splenium FA was positively related to social gaze at 12m (b = 0.45, 95% CI [0.05, 0.86], p = 0.028) and matrix reasoning (i.e., visual pattern recognition) at follow-up (b = 0.41, 95% CI [0.11, 0.71], p = 0.008) among HL children who developed ASD (HL-ASD), associations that were much weaker or non-existent in TD children. Cortical SA in several visual regions was negatively associated with autistic social behavior in HL-ASD children at follow-up, especially in secondary visual cortex (b = −1.02, 95% CI [−1.52, −0.52], p < 0.0001), such that larger SA was associated with a milder social phenotype. Maternal social behavior explained ~30% of the variance in infant secondary visual cortical SA in HL-ASD.

Conclusions: Features of visual cortical circuitry are related to genetic liability and associated with aspects of social behavior and visual-cognitive processing among infants and children with ASD. This suggests that the visual system develops atypically in ASD and may play a unique role in cognition and social behavior not observed in typical development.

Disclosure: Nothing to disclose.

7.3 Impact of early adverse exposures on brain development and child psychopathology: insights from longitudinal MRI studies

Cynthia Rogers

Washington University School of Medicine, St. Louis, Missouri, United States

Background: Mounting data supports the effects of early adverse exposures on child psychopathology. The impact that various early adverse exposures have on the trajectory of structural and functional brain development beginning at birth through adolescence and how these alterations may mediate the development of psychopathology is less well studied. Data from three longitudinal studies relating adverse exposures (preterm birth, social disadvantage, and prenatal cannabis use) to childhood psychopathology are discussed.

Methods: These studies include more than 500 caregiver-infant dyads recruited during pregnancy or near birth with measures of income, neighborhood poverty, and maternal psychopathology. Infants had MRI scans as neonates, during early childhood and/or up to ages 14–15. Structural, diffusion, and function MRI scans were obtained and analyzed to extract measures of volume, diffusion metrics and functional connectivity. Anatomically-Constrained Multimodal Surface Matching was used to compute cortical expansion between time points. Child social-emotional development was assessed with parent-report measures, and semi-structured interviews. Early adversity variables were related to brain measures and assessments of psychopathology.

Results: Greater prenatal social disadvantage (PSD) was linked to greater age 2 externalizing and dysregulating symptoms. PSD-linked reductions in neonatal brain volumes mediated both PSD-externalizing and PSD-dysregulating relations. PSD linked to greater mean cortical expansion from 0 to 3 in the insula and medial frontal lobe (ps < 0.05). Cortical expansion increased from 0 to age 9–10 and decreased from age 9–10 to14–15 with greater expansion among those born very preterm (<30 weeks). Less global cortical expansion from 0 to age 9–10 was linked to more ADHD, anxiety, and ASD symptoms. Prenatal cannabis exposure was linked to differential functional connectivity between cannabinoid receptor rich regions (amygdala, hippocampus, cerebellum, striatum) and prefrontal regions, diffusion measures linking these regions, (ps < 0.05) and to more childhood externalizing symptoms (p < 0.02).

Conclusions: Early adversity significantly affects brain development from birth through age 15 which then mediates psychopathology. Addressing these can reduce long-term impacts on mental health.

Disclosure: Nothing to disclose.

7.4 Precision functional mapping of the individual human brain near birth

Alyssa Labonte

Washington University in St. Louis, St. Louis, Missouri, United States

Background: Many psychiatric disorders originate from individual differences in early functional brain development. Thus, models of psychiatric disorders likely require tracking personalized brain functional organization and development from birth onwards. Yet, little is known about whether functional brain development can be reliably tracked in individual humans or when individual differences first emerge. Here, we collect large amounts of fMRI data in individual neonates to perform precision functional mapping (PFM), a technique used in adults to capture reliable individual-specific functional brain properties. We test feasibility and reliability of neonatal PFM and examine whether there are individual differences in functional brain organization already near birth.

Methods: Each PFM dataset (n = 8, n = 5 male) was split into two roughly equal halves of data from different days to measure within-subject reliability and across-subject similarity of whole-brain functional connectivity (FC) and cortical area organization. Individual areal organization was derived using FC boundary mapping.

Results: Infants tolerated an average of 99.5 minutes (range 40.2–154.1) of scanning over 2–5 consecutive days, with an average of 77.9 minutes (range 36.6–143.8) of low-motion data (FD < 0.1-mm). Whole-brain patterns of FC reached a median within-subject, across-day reliability of r = 0.78 with 41.9 minutes of data. Across subject similarity was r = 0.62 on average and significantly lower than within-subject similarity using data from different days (p < 0.001). Areal organization was individually reliable across split-halves (p < 0.001) but areas derived for one individual performed poorly in other individuals (in 29/30 across subject comparisons, p > 0.01).

Conclusions: Neonatal PFM is feasible and measures reliable, individually specific brain organization. There is substantial individual variation in brain organization (cortical area arrangement) already near the time of birth. Viable developmental models of psychiatric disorders will thus require tracking individualized functional brain trajectories. Future work can determine whether individual variation in brain organization present near birth relates to psychiatric risk.

Disclosure: Nothing to disclose.

Mini Panel

8. Rethinking Striatal Organization and Function—Exploring the Emerging Roles of Unique Striatal Subpopulations in Health and Disease

8.1 3D Anatomical mapping and functional characterization of striatal dopamine receptor heterogeneity

Jenesis Kozel

University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Background: Striatal dopamine (DA) neurotransmission is heavily involved in goal-directed behaviors, motivations, and reward-seeking. Consequently, its dysfunction is also implicated in a wide variety of neuropsychiatric diseases, including substance use disorders and schizophrenia. The striatum is composed of GABAergic spiny projection neurons (SPNs) that traditionally have been categorized into two subpopulations based on the expression of either D1-like receptors or D2-like receptors. These receptors differ on several levels, including in cellular, circuitry, and behavioral characteristics. More recent evidence demonstrates that there are SPNs that co-express multiple DA receptor subtypes, suggesting that SPN subpopulations may not be as dichotomous as previously thought. Due to past technical limitations, these co-expressing SPN subpopulations are not as well-characterized as their sole expressor counterparts. Thus, we aimed to further characterize co-expressing SPN subpopulations using a combination of imaging, transcriptomic, and physiology methods.

Methods: We used multiplex RNAscope in situ hybridization to map DA receptor mRNA expression of the most widely expressed striatal DA receptors, D1R, D2R, and D3R, in 3D across both dorsal-ventral and rostral-caudal axes in adult mouse striatum. In parallel, we conducted multi-species transcriptomic analyses, including new RNA-seq data from human nucleus accumbens, to generate a merged transcriptomic atlas of SPNs based on DA receptor identities. We generated a new mouse line, Drd1Cre/+; Adora2aFlpO/+, to selectively label and target SPNs that express both D1R and D2R (D1/2R SPNs) versus SPNs that express only D1R (D1R-only) in the same brain via viral expression. After confirmation via ribbon-scanning microscopy of cleared whole brains and immunohistochemistry, we utilized electrophysiology to measure active and passive membrane qualities of D1/2R and D1R-only SPNs.

Results: Our RNAscope mapping confirms distinct subpopulations of SPNs based on DA receptor mRNA expression including several co-expressing populations: D1/3R, D1/2R, and D2/3R. We find graded expression of co-expressing SPNs distinct from SPNs that express only one DA receptor subtype, with enrichment of these subpopulations in the ventral striatum. Transcriptomic analyses reveal that these SPN subpopulations are transcriptomically unique from one another and are conserved across species from rodents to monkeys to humans. Using NeuroEstimator, a deep learning model that uses single-cell gene expression profiles to infer neuronal activity, we hypothesized that co-expressing D1/2R SPNs have a unique electrophysiological profile compared to D1R-only SPNs. Our electrophysiological studies confirm our hypothesis, showing that D1/2R SPNs have significantly higher spontaneous and evoked firing frequencies vs D1R-only neurons (*p < 0.05, **p = 0.0074).

Conclusions: Overall, this work definitively maps SPN DA receptor expression across adult mouse striatum. We show that SPNs that co-express multiple DA receptors have unique spatial and transcriptomic qualities distinct from SPNs expressing only one DA subtype. Focusing on D1/2R SPNs, we further find that these differences can translate to cellular function, presenting an opportunity for further studies of these neurons’ roles in behavior in health and disease.

Disclosure: Nothing to disclose.

8.2 Atypical nucleus accumbens neurons locally regulate dopamine and shape opioid withdrawal and relapse behaviors

Jason Tucciarone

Stanford University School of Medicine, Stanford, California, United States

Background: The opioid epidemic creates an urgent demand for effective treatments for opioid use disorder. The negative emotional state of withdrawal, along with environmental cues linked to opioid use, strongly contributes to relapse and elevates the risk of overdose. Although dopamine (DA) signaling in the nucleus accumbens (NAc) is known to increase during drug use and decrease during withdrawal, the precise neural circuits underlying these shifts remain unresolved and are the subject of ongoing debate. Finally, recent transcriptomic studies have uncovered greater cellular diversity within motivation-related circuits, suggesting that distinct cell types may play specific and critical roles across different stages of addiction and opioid use disorder.

Methods: We used female and male wild-type and transgenic mice to study cell-type-specific mechanisms in opioid use and withdrawal. Single-cell RNA sequencing of mouse NAc and human striatum identified distinct cell populations. Morphine induced dependence and withdrawal (n = 10–20), while neural activity was monitored with dopamine and calcium sensors (n = 6–8) and manipulated using opto- and chemogenetics (n = 8–14). Cre-mediated deletion of opioid receptors targeted specific neuronal types (n = 10–16). Withdrawal aversion was tested via naloxone-induced CPA (n = 8–16), and fentanyl self-administration, extinction, and reinstatement were paired with chemogenetic tools to probe behavioral regulation (n = 8–10).

Results: Morphine withdrawal produced robust behavioral aversion and a marked decrease in dopamine (DA) release within the nucleus accumbens (NAc). In vivo recordings confirmed strong inhibition of DA axon activity during withdrawal, independent of midbrain GABAergic inputs. Single-cell RNA sequencing identified a distinct NAc cell population co-expressing the highest transcript level of mu opioid receptor (Oprm1) and dopamine receptor D1 (Drd1), but largely lacking the canonical marker dynorphin (Pdyn). Instead, this population was defined by high expression of the transcription factor Tshz1 and was also observed in human striatal tissue. Tshz1 neurons were suppressed by morphine but exhibited rebound excitation during withdrawal. In naive mice, activating Tshz1 neurons strongly inhibited DA release in the NAc via local GABAergic signaling onto DA axons. Targeted chemogenetic inhibition or Oprm1 deletion in these cells prevented both withdrawal-induced aversion and DA suppression. Further, Tshz1 expressed a cellular specific, druggable GPCR that when agonized led to reduced withdrawal aversion. Finally, chemogenetic excitation of NAc Tshz1 neurons during fentanyl IV self administration led to accelerated extinction and reduced reinstatement with ongoing experiments delineating the effects of chemogenetic inhibition.

Conclusions: These findings reveal Tshz1 neurons as a conserved and functionally distinct D1 medium spiny neuron population that modulates DA signaling during opioid withdrawal and suggest a novel, cell-type-specific therapeutic target for alleviating withdrawal symptoms and reducing relapse risk.

Disclosure: Headlamp Health, Consultant, Self

8.3 Circuit tuning across species: dopamine and serotonin in the basal ganglia

Veronica Alvarez

NIH/NIMH, Bethesda, Maryland, United States

Background: Therapeutic drugs targeting serotonin (5-HT) and dopamine (DA) receptors are widely used to treat or alleviate symptoms of neurodevelopmental and neuropsychiatric disorders, including ADHD, depression, anxiety, PTSD, OCD, and schizophrenia. However, the precise mechanisms by which these drugs and their target neuromodulators exert their effects remain poorly understood. As monoamines, serotonin and dopamine play critical roles throughout the brain, particularly in the basal ganglia, where their densely expressed receptors regulate sensory processing, motor control, and motivation.

Recent genetic studies have uncovered greater-than-anticipated diversity among striatal neurons, both medium spiny neurons and interneurons, prompting a renewed evaluation of serotonin and dopamine signaling in this region. Although these neuromodulatory systems share an evolutionary origin, with homologous receptors and synthetic pathways, they have diverged across species to support distinct roles in emotional, sensory, and motor functions. As a result, findings from rodent models may not fully capture the complexity of striatal neuromodulation in primates. Targeted studies in non-human primates are therefore critical to elucidate the specific roles of serotonin and dopamine in the primate striatum and advance our understanding of neuromodulation in the human basal ganglia.

Methods: The study employs enhancer-AAVs to target distinct subpopulations of striatal neurons in both mice and macaques, combined with ex vivo slice electrophysiology, voltammetry, and photometry to assess how exogenously and endogenously released dopamine and serotonin influence synaptic strength and plasticity across neuronal subclasses and species.

Results: The experiments demonstrate that in the mouse basal ganglia, dopamine can modulate synaptic strength through its action on serotonin receptors, revealing an unexpected level of cross-talk between these neuromodulatory systems. We are currently investigating whether a similar mechanism exists in the macaque. Our goal is to identify both shared and distinct features of serotonin and dopamine modulation in the basal ganglia across rodents and primates.

Conclusions: The study identifies both shared and divergent aspects of dopamine and serotonin neuromodulation in the basal ganglia of rodents and macaques. These findings offer new insights into the cellular mechanisms underlying serotonin-enhancing antidepressants and their effects on basal ganglia circuitry.

Disclosure: Nothing to disclose.

Study Group

9. Centering Lived Experience in Psychiatric Neuroscience Research: Challenges, Opportunities, and Calls to Action

Eric Nestler, Brandon Staglin, Uma Chatterjee, Maya Schumer, Devin Effinger, Nev Jones, Noel Vest

Icahn School of Medicine at Mount Sinai, New York, New York, United States

Study Group Summary: The increasing participation of researchers with lived experience (PWLE) of serious mental illness (SMI) is reshaping psychiatric neuroscience. Researchers who openly live with SMIs, such as obsessive compulsive disorder (OCD), bipolar disorder, schizophrenia, substance use disorder (SUD), post-traumatic stress disorder (PTSD), and major depressive disorder (MDD), add essential pluralism: they integrate scientific, experiential, and critical knowledge and expose blind spots in prevailing animal models, imaging paradigms, and clinical metrics. Their work highlights the complexity and lived realities of psychiatric disorders and challenges persistent binary notions of “normal vs. abnormal.” Despite having unique insights that can advance scientific merit, PWLE expertise is too often discounted and marginalized; stigma and epistemic injustice continue to deter disclosure and limit career advancement.

With dimensional and transdiagnostic frameworks increasingly embraced in psychiatric research, integrating and centering lived experience is vital for maximizing comprehensive inquiry. Still, PWLE scientists must decide when and how to disclose diagnosis, secure appropriate accommodations, and counter perceptions that they are a “risk” or “red flag.” Institutions, funding agencies, and journals alike must acknowledge and address the systemic biases that devalue contributions by PWLE.

This Study Group will examine the impact of lived experience on research quality and translational relevance. Some of the panelists are researchers with lived experience of SMI across various career stages who will share how their lived experience has informed their research methods and measures, reframed data interpretation, and reconceptualized dominant models of their condition. Discussion will focus on governance structures—shared decision-making committees, joint authorship guidelines, and budget authority—that can move the field from tokenistic inclusion toward genuine power-sharing. Attention will also be given to ethical considerations, community trust, and evaluation metrics that extend beyond publications and grants.

International efforts to mainstream lived experience involvement in mental health research in the U.K., Australia, and U.S. public-sector research show that meaningful coproduction can accelerate translation to clinical practice. Principal investigators without lived experience who mentor PWLE trainees will speak to why this is not a “risk,” but an investment in the future of the field; their outcomes demonstrate that such inclusion improves scientific quality and broadens research impact.

The session concludes with a call for structural and systemic change: policies that protect early disclosure, dynamic accommodation guidelines, funding mechanisms that prioritize meaningful coproduction, and upliftment of PWLE leadership at every career stage. By advancing epistemic justice, complexity-oriented methodologies, and authentic power-sharing, ACNP can position psychiatric neuroscience and aligned fields for more rigorous, inclusive, and clinically-relevant discovery. This first-of-its-kind Study Group presents an opportunity for ACNP to lead the global shift toward scientifically-grounded, complex, lived-experience-informed mental-health research.

Disclosure: Nothing to disclose.

Panel

10. Prospects of Novel GLP-1 Therapies for Addictions: What’s All the Hype About and Where Do We Go From Here?

10.1 Effects of GLP-1R and GIPR agonism on binge-like alcohol drinking in male and female mice

Howard Becker

Medical University of South Carolina, Charleston, South Carolina, United States

Background: Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are incretin hormones, and drugs targeting their receptors (GLP-1R and GIPR, respectively) are used in treatment of diabetes and obesity. Recent preclinical and clinical evidence has emerged indicating these drugs can reduce alcohol consumption. Here, we assess the effects of the dual GLP-1R/GIPR agonist tirzepatide (TZP) on alcohol consumption in a binge-like drinking model and examine the ability of GLP-1R and GIPR antagonists to reverse the effects of TZP.

Methods: Adult male and female C57BL/6J mice were given 2-hr access to alcohol (20% v/v) for three consecutive days and on Day-4 access was extended to 4-hr. This 4-day procedure was repeated over several weeks. Mice (N = 9–10/dose/sex) received injections (ip.) of vehicle 4-hr prior to drinking sessions on Days 1–3 and TZP (0, 0.018, 0.036, 0.072 mg/kg) on Day 4. The same doses were used to examine effects on sucrose (1% w/v) intake in the same paradigm. Separate mice were used to test the effects of a cocktail of GLP-1R (extendin9–39; 0.84 mg/kg) and GIPR (Pro-GIP; 0.124 mg/kg) antagonists against TZP (0.018 mg/kg) on alcohol intake. The dual antagonist was given 30-min prior to the 4-hr TZP pretreatment.

Results: TZP significantly reduced alcohol intake in a dose-related manner [Dose: F(3,72) = 26.40, p < 0.001)], and this effect was similar in males (74–87% reduction) and females (55–98% reduction). Likewise, TZP reduced sucrose intake in a dose-related manner [Dose: F(3,72) = 66.81, p < 0.001)], and this effect was similar in males (47–82% reduction) and females (48–80% reduction). In males and females the combined GLP-1R/GIPR antagonist cocktail attenuated reduced alcohol intake produced by TZP (0.018 mg/kg) [Group: F(3,69) = 56.58, p < 0.001)].

Conclusions: The dual GLP-1R/GIPR agonist TZP reduced alcohol consumption in a dose-related manner in a binge-like drinking paradigm, with similar potency and efficacy in males and females. TZP also significantly reduced sucrose intake. Finally, a dual GLP-1R/GIPR antagonist cocktail was found to attenuate the ability of TZP to reduce alcohol consumption. Collectively, these data provide important information regarding the conditions under which these drugs may alter alcohol consumption and mechanisms that mediate such effects.

Disclosure: Epivario, Contracted Research, Self, NeuroEpigenix, Consultant, Self, Alkermes, Contracted Research, Self, Kuleon Bioscience, Consultant, Self

10.2 Repurposing the GLP-1 receptor agonist (GLP-1RA) semaglutide for alcohol and opioid use disorder: recent evidence from rodent and human studies

Abstract Not Included

10.3 Real world evidence on GLP-1 receptor agonists and substance use disorders

Jingchuan Guo

Purdue University, Indianapolis, Indiana, United States

Background: Glucagon-like peptide-1 receptor agonists (GLP-1RA), approved for type 2 diabetes (T2D) and obesity treatment, may modulate reward pathways and reduce substance-related behaviors. This study assessed the association between GLP-1RA use and hospitalization risk for substance use disorder (SUD), including alcohol use disorder (AUD) and opioid use disorder (OUD), in older adults with comorbid T2D and SUD.

Methods: A retrospective cohort study using 2016–2020 Medicare data assessed the association between GLP-1RA use and substance use–related hospitalizations among adults aged ≥ 65 years with comorbid T2D and SUD at baseline. GLP-1RA initiators were compared to new users of sodium-glucose cotransporter 2 inhibitors (SGLT2I) or dipeptidyl peptidase-4 inhibitor (DPP-4I). The primary outcome was hospitalization for any SUD; secondary outcomes included hospitalizations for AUD and OUD.

Results: A total of 4,620 matched patients were included in the GLP-1RA vs SGLT2I cohort, and 4920 in the GLP-1RA vs DPP4I cohort. In the GLP-1RA vs SGLT2I cohort, the incidence rate of SUD hospitalization was similar between groups (160.17 vs 161.47 per 1000 person-years). In contrast, in the GLP-1RA vs DPP4I cohort, GLP-1RA users had a lower incidence rate (67.53 vs 75.76 per 1000 person-years). Compared to DPP4I, GLP-1RA use was associated with a lower risk of hospitalization for SUD (HR, 0.76; 95% CI, 0.67–0.86) and OUD (HR, 0.64; 95% CI, 0.43–0.96). A reduction in AUD hospitalization risk was also observed but it was not statistically significant (HR, 0.76; 95% CI, 0.53–1.08).

Conclusions: In this study of older adults with T2D, compared to DPP4I, GLP-1RA use was associated with lower risk of SUD hospitalizations, suggesting potential for repurposing these agents in SUD treatment and highlighting the need for validation in future research.

Disclosure: Nothing to disclose.

10.4 Considering the blood-brain barrier with GLP-1 receptor agonists

Elizabeth Rhea

University of Washington, Seattle, Washington, United States

Background: One way GLP-1 receptor agonists (GLP-1RAs) can act within the brain is by crossing the blood-brain barrier (BBB). The BBB is a selective, semi-permeable structure regulating substrate entry from blood to brain. BBB penetration allows for direct action within the brain. We characterized the BBB penetration of 13 GLP-1 receptor agonists, identified physiochemical properties regulating this transport, examined the regional transport rates, and identified the impact on the BBB.

Methods: We radioactively labeled each GLP-1RA and measured BBB transport following intravenous injection in young, CD-1 male mice, accounting for vascular volume (n = 10–18). In follow up studies, we investigated the regional transport rates in male and female mice (n = 6/sex), as well as the acute (co-administration) and long-term (two weeks) effects of GLP-1RA treatment on BBB function (n = 6/sex), by assessing insulin BBB transport. We used multiple time linear regression analysis to calculate and compare the transport rates.

Results: Of the 9 GLP-1RAs that were transported within 1 hour, there was a 27-fold difference in the rates of transport. The biological active fragment (BAF) of dulaglutide exhibited varying regional transport rates (p = 0.001), with the frontal cortex and olfactory bulb exhibiting some of the faster rates of transport. The presence of excess insulin enhanced the transport rate for dulaglutide (BAF) into the whole brain (p = 0.047). Semaglutide treatment either acutely (Vi, p = 0.043) or long-term (Ki, p = 0.025) reduced insulin BBB interactions specifically in female mice.

Conclusions: Our work has identified GLP-1RAs enter the brain at varying rates, that acylation retards BBB transport, and lipophilicity and molecular weight correlate with transport rates. Regional differences in transport rates exist, that are differentially mediated by insulin levels. Indirect mechanisms, such as actions at the BBB, may also play a role in the central effects of GLP-1RAs and these mechanisms appear to differ by sex.

Disclosure: Nothing to disclose.

Panel

11. Closing the Gap: Understanding Sex-Specific Mechanisms in Reward, Decision-Making, and Addiction

11.1 Sex differences in decision making emerge from stable behavior

Nicola Grissom

University of Minnesota, Minneapolis, Minnesota, United States

Background: Cognitive flexibility requires individuals to adaptively shift between rules based on environmental feedback, but it also requires stable performance of an adopted rule when feedback is clear. The continuous transitions between flexible and stable choices may be supported by the computational mechanisms underlying the explore-exploit tradeoff. One critical variable well known to influence individual differences in neuropsychiatric risk is sex, and sex differences have been previously seen in explore-exploit tradeoffs, but whether sex reflects a major source of variation in cognitive flexibility remains unknown.

Methods: To directly assess sex-biased individual differences in cognitive flexibility, we developed a novel touchscreen Set Shift task that permits robust and continuous testing in mice (32 mice (16 male/16 female, wildtype strain B6129SF1/J). Following training and testing, we employed a suite of computational models (reinforcement learning, drift diffusion, and hidden Markov models) to identify latent contributions to sex-biased individual differences in the computations underlying cognitive flexibility.

Results: Female mice completed significantly more rule shifts with fewer errors than males. Sex differences were found in choice precommitment and value updating, and hidden Markov modeling revealed that females were more likely to transition from exploration into a new rule state. Following rule shifts, female mice learn the new rule faster and commit to exploiting rule choices sooner compared to males–sometimes because they commit to multiple rules simultaneously.

Conclusions: Increased choice stability in female rodents enhances commitment to a strategy during periods of uncertainty and directly contributes to improved performance in a set shifting task. These findings suggest that the stability of decision making as a result of prior outcomes may be an underrecognized variable supporting cognitive flexibility, and that differences in this aspect of explore-exploit computations may underlie individual differences in neuropsychiatric risk and resilience.

Disclosure: Nothing to disclose.

11.2 Estradiol potentiates dopamine release through estrogen-receptor-independent actions on nicotinic acetylcholine receptors

Erin Calipari

Vanderbilt University, Nashville, Tennessee, United States

Background: For many psychiatric disorders, sex is a critical biological variable and the mesolimbic dopamine system is causally linked to these phenotypes in addiction, depression, anxiety, and other conditions. While work has focused on sex differences in relative dopamine levels and the anatomy of this system, an important characteristic of dopamine release in the nucleus accumbens (NAc) is that it is rapidly modulated through nicotinic acetylcholine receptors (nAChRs) located directly on dopamine axons. This effect is striking, widely reproduced, and plays a critical role in cognition and learning. We show that this effect is absent in intact adult females and changes how acetylcholine-dopamine interactions control behavior.

Methods: Using subsecond dopamine recordings—in males, intact females, and ovariectomized females—paired with pharmacology and behavior we outlined how nicotinic receptors regulate dopamine release across groups and how estradiol influences these effects. Using operant behavior, chemogenetic approaches, and nicotine self-administration we outlined how changes in dopamine-acetylcholine interactions influenced motivated behavior and decision-making.

Results: Cholinergic modulation of dopamine release was not present in adult intact females. In defining the mechanism underlying these sex differences, we identified an estradiol binding site on nAChRs that overlaps with binding sites for other known nAChR agonists. In males and ovariectomized females, estradiol increases dopamine release through potentiation of nAChRs. These receptors desensitization when potentiated, and, indeed, both estradiol actions and the regulation of dopamine release through this mechanism are absent in intact females. We link this sex difference in this receptor function to motivated behavior for both non-drug and drug reinforcers.

Conclusions: Overall, we show that estradiol has rapid, non-estrogen receptor-mediated, effects through nAChRs that alter the relationship between dopamine and acetylcholine in females. We find that nAChR regulation of dopamine release is not present in intact females under most conditions. Finally, using chemogenetic approaches in awake and behaving animals, we link these sex differences to sex-specific motivated behaviors.

Disclosure: Nothing to disclose.

11.3 Precision mapping of the role of sex differences and sex hormones in reward value computations in human opioid addiction

Anna Konova

Rutgers University - New Brunswick, Piscataway, New Jersey, United States

Background: The opioid epidemic remains a serious global health crisis that has, among other vulnerable groups, disproportionately impacted women, who experience higher rates of relapse and early treatment dropout than men. To personalize treatments and improve outcomes for women, we must first understand the mechanisms and factors contributing to opioid reuse vulnerability in women. Prior work suggests dopamine-mediated decision-making indices of reward learning and valuation precede and follow states of increased opioid vulnerability (reuse, craving), in line with a central role of these neurocognitive processes in addiction and relapse across substances. Here, we examined whether these processes are subject to sex-specific influences, which could explain the divergent outcomes observed in women.

Methods: In Study 1, tying repeated fMRI scanning to phases of the menstrual cycle in women (N = 12, n = 5 with opioid use disorder (OUD); range: 3–6 MRIs/participant, total of 65 [data collection ongoing]), we examined how within-person fluctuations in sex hormones interact with neural computations of the value of risky rewards on a validated decision-making task. In Study 2, using daily ecological momentary assessments (EMA) over 28 days in treatment-engaged OUD participants (N = 67, n = 25 women) and controls (N = 52, n = 27 women), we assessed for sex differences in drug craving, drug-cue/context exposure, and subsequent drug-use events in participants’ natural environments, and the mediating role of changes in reward-based decision-making.

Results: Within-person increases in estradiol levels correlated with increased risk tolerance on the decision-making task. These changes in behavior paralleled increased sensitivity to the value of risky rewards in the ventromedial prefrontal cortex and ventral striatum, brain regions innervated by estrogen-sensitive dopaminergic pathways. In the EMA study, exposure to drug cues in daily life predicted both increased risk-taking behavior and next-day drug use, with effects stronger in women.

Conclusions: Our findings show sex and hormonal fluctuations influence reward-based decision-making and cue sensitivity, key dopamine-mediated processes implicated in addiction, which may help explain the heightened vulnerability to relapse and treatment challenges among women with OUD.

Disclosure: Nothing to disclose.

11.4 Sex and hormonal effects in prefrontal cortical cue reactivity, emotion regulation, and naturalistic drug-biased processing in human drug addiction

Abstract Not Included

Panel

12. Antidepressant Efficacy and Mechanisms of Pramipexole

12.1 Efficacy and mechanisms of high-dose pramipexole for anhedonic depression

Daniel Lindqvist

Lund University, Lund, Sweden

Background: We propose that dopamine D3 agonist pramipexole could be an effective treatment for anhedonic depression. Clinical observations have shown that high-dose pramipexole can lead to significant improvement in patients with treatment resistant depression. Existing research indicates that D3 receptor agonism, especially at higher doses, may enhance reward responsiveness and reduce anhedonia. Pramipexole improves anhedonia and related symptoms in patients with Parkinson's disease (PD) and may help normalize reduced dopaminergic activity also in individuals with non-PD anhedonic depression. The main aim of this study is to demonstrate that high-dose add-on pramipexole is efficacious in a subtype of depression with anhedonic features.

Methods: Patients with unipolar depression, dysthymia or bipolar depression were randomized to receive either add-on flexible-dose pramipexole or identical placebo for nine weeks. All patients had significant anhedonia, per the Snaith-Hamilton Pleasure Scale (SHAPS). Primary outcome measure was change in the SHAPS. A subset of the patients underwent fMRI with the Monetary Incentive Delay Task pre/post treatment. We used linear mixed model with repeated measures (week 3, week 6 and week 9) to test if pramipexole outperforms placebo on the primary outcome.

Results: 82 patients with at least one post-baseline were included in the intention-to treat sample. One of these patients only reached week 3 and one of these patients only reached week 6. Missing data for these two patients were imputed using last observation carried forward.

At the 9-week primary endpoint, the mean decrease in SHAPS score from baseline in the pramipexole group was 6.5 points compared to 2.4 in the placebo group. The difference in mean change was 4.1 (95% CI −6.9 to −1.2, p = 0.005). The effect size according to Hedge's g was 0.63.

We will now analyze the secondary outcomes including fMRI data, and this will be presented at the meeting if the proposal is accepted.

Conclusions: Our results suggest that pramipexole is efficacious for treating anhedonic depression.

Disclosure: Eli Lilly, Stock / Equity - Publicly Traded Company, Self

12.2 A behavioral and molecular profile of reward function predicts response to pramipexole in individuals with major depressive disorder

Alexis Whitton

University of New South Wales, Randwick, Australia

Background: Dopaminergic dysfunction has been implicated in the pathophysiology of major depressive disorder (MDD), particularly in symptoms related to reward processing, such as anhedonia. The dopamine D3-preferring agonist pramipexole (PPX) has shown antidepressant effects, but the neurobiological mechanisms supporting this response remain unclear. This study tested whether behavioral, functional, and molecular measures of reward processing relate to clinical response to PPX in MDD.

Methods: Twenty-six unmedicated adults with MDD and 26 healthy controls (50% female) completed a probabilistic reward task (PRT) at baseline. Individuals with MDD repeated the PRT after six weeks of open-label PPX treatment (0.5–2.5 mg/day). Depression (HAM-D), anhedonia (SHAPS) and global illness severity (CGI) were assessed weekly. Participants also underwent fMRI during a reinforcement learning task to assess striatal reward prediction error (RPE) signaling, and PET imaging with [¹¹C]-(+)-PHNO to quantify D2/D3 binding potential (BPND).

Results: MDD participants showed blunted PRT response bias at baseline relative to controls. While response bias did not improve from pre- to post-treatment, higher baseline response bias predicted greater reductions in anhedonia (SHAPS scores) post-PPX (β = −0.77, p = 0.001). Similarly, stronger baseline striatal RPE signals predicted greater week-on-week improvement in global illness severity following PPX (p = 0.004). PET imaging revealed that a lower BPND ratio in ventral pallidum (a D3-rich region that [¹¹C]-(+)-PHNO binds to with high affinity) relative to caudate (a D2-dominant region) – suggestive of lower D3 or relatively higher D2 receptor availability – was associated with greater baseline anhedonia (r = −0.50, p = 0.02) and greater week-on-week improvement in anhedonia, depression and global illness severity following PPX (all ps < 0.02).

Conclusions: Together, these findings suggest that individuals with relatively preserved phasic reward signaling but reduced D3 receptor availability may derive greater benefit from D3-preferring agonists like PPX. This pattern points to a potential mechanism wherein PPX may enhance tonic motivation through D3 receptor stimulation in individuals who retain sensitivity to reward cues, helping to clarify dopaminergic contributions to anhedonia and PPX response.

Disclosure: Nothing to disclose.

12.3 Circuit-based precision medicine for reward circuit dysfunction in depression: from retrospective discovery to prospective validation

Teddy Akiki

Stanford University School of Medicine, Palo Alto, California, United States

Background: Major depressive disorder is a heterogeneous condition, and first-line treatments are ineffective for a substantial portion of patients. Anhedonia, a core symptom reflecting reward circuit dysfunction, predicts poor response to standard antidepressants. We hypothesized that baseline reward circuit function could guide treatment selection more effectively than symptoms. We present three complementary studies examining whether reward circuit dysfunction predicts response to traditional antidepressants and a dopaminergic intervention.

Methods: For functional MRI data, the Stanford EtCere pipeline was used to compute personalized measures of brain circuit function for each participant, normalized to healthy references. Reward circuit activity/connectivity assessed via ventral striatum (VS) and ventromedial prefrontal cortex (vmPFC) function during emotional faces task.

Study 1: Retrospective analysis of iSPOT-D trial (n = 198; 51% female) randomized to SSRI (escitalopram, sertraline) or venlafaxine. Using logistic regression models, we tested if baseline circuit function predicted treatment response.

Study 2: Open-label pilot of pramipexole (target = 2mg/day) in 5 MDD patients (20% female) with prominent anhedonia (MASQ-A > 35).

Study 3: A prospective trial (SPARCLE; target n = 60) was initiated, enrolling individuals meeting criteria for moderate-to-severe MDD, not pre-selected for anhedonia. The study was designed with the pre-specified hypothesis that individuals with baseline reward circuit dysfunction would preferentially respond to pramipexole.

Results: Study 1: In SSRI-treated patients, baseline reward circuit dysfunction predicted non-response (p = 0.03, AUROC = 0.68).

Study 2: Pramipexole improved anhedonia (p = 0.02, d = 2.0) and depression (p = 0.05, d = 1.5), and increased VS activation (p = 0.05, d = 1.3).

Study 3: The prospective trial is ongoing to test if reward circuit function identifies pramipexole responders.

Conclusions: These findings show a translational path to clinical use. Baseline reward circuit function can be a predictive biomarker identifying MDD patients unlikely to respond to standard antidepressants. For these patients, the dopamine agonist pramipexole is a promising alternative. The ongoing SPARCLE trial is critical to validate this precision approach for patient stratification.

Disclosure: Nothing to disclose.

12.4 Pramipexole augmentation for acute phase and maintenance therapy of treatment-resistant depression: a placebo-controlled, randomized trial

Michael Browning

University of Oxford, Oxford, United Kingdom

Background: There has been interest in the use of dopaminergic agonists in patients with treatment resistant depression (TRD), although they have only been assessed in small-scale, short-term studies. We assessed the effect and safety/tolerability of the dopamine agonist pramipexole in a substantial randomized controlled trial.

Methods: Male and female participants, aged ≥18, who had not responded to at least two antidepressants were recruited from 9 UK sites. Participants were randomized to 48 weeks of either pramipexole or placebo augmentation, with doses titrated up to 2.5mg daily. The primary outcome was change in the QIDS-SR scale to week 12. Secondary outcomes included change in symptoms of depression, anhedonia (SHAPS) and functioning (WSAS) over 48 weeks, as well as dropout rates due to intolerance. 150 eligible participants were randomized (n = 75 per group, 56% female). Pre-specified, intention to treat analyses using mixed-effect models will be presented.

Results: Mean (SD) QIDS-SR score at baseline was 16.4 (3.4) in the pramipexole group and 16.2 (3.5) in the placebo group. By week 12 these scores had reduced by a mean 6.4 in the pramipexole group and 2.4 in the placebo group (difference 3.9 [CI 5.4–2.5], d = 0.89, p < 0.0001). All other secondary efficacy outcomes were significant in favor of pramipexole, up to final assessment at week 48. Significantly more people in the pramipexole group discontinued treatment due to side effects (15 (20%) vs. 4 (5.3%), p = 0.01).

Conclusions: Pramipexole augmentation was effective at reducing symptoms of depression across the course of a year. The effect size was large, comparing favorably to that reported for other common interventions for TRD. Adverse effects limited the use of pramipexole in 20% of patients.

Disclosure: Alto Neuroscience, Consultant, Self, Empyrean Neuroscience, Consultant, Self, J and J, Consultant, Self, Engrail Therapeutics, Consultant, Self.

Panel

13. Sleep, Mood, and Arousal Symptoms in Early Alzheimer's Disease: Focus on Brainstem Monoaminergic Circuits

13.1 Selective vulnerability of serotonergic neurons to tau pathology and hyperexcitability: implications for neuropsychiatric symptoms in Alzheimer’s disease

Catherine Marcinkiewcz

University of Florida College of Pharmacy, Gainesville, Florida, United States

Background: Alzheimer's disease (AD) is preceded by prodromal neuropsychiatric symptoms (NPS), during which time early intervention may be possible but not yet realized. Elucidating the neuronal populations involved in prodromal AD is a key area for research into early diagnosis and prevention. The present study assessed the role of serotonin (5-HT) neurons in the dorsal raphe nucleus (DRN) in behavioral changes associated with early AD and identified neuronal populations that may be driving those changes in two distinct mouse models.

Methods: Sert-cre mice aged 8–12 weeks (N = 16 per group) were injected with AAV-FLEX-P301Ltau or AAV-FLEX-mCherry in the DRN prior to behavioral testing at 4 and 8 weeks (EPM, open field, social interaction, sucrose preference, novelty suppressed feeding (NSF), Y Maze, and Novel Object Recognition (NOR)). Promethion metabolic chambers were used to assess food/water intake, activity, and O2/CO2 exchange. REM/non-REM sleep and spectral power analysis were examined with EEG/EMG recordings in a separate cohort.

The Visium platform was used to identify genes implicated in tau aggregation and hyperexcitability in the DRN of 16-week-old Htau and C57 mice (N = 4 per group). Gene expression was validated by RNAscope and immunofluorescence, and whole-cell patch clamp electrophysiology was used to assess excitability in 5-HT subpopulations.

Results: Viral induction of tau pathology in 5-HT neurons resulted in a persistent increase in non-REM sleep duration and bout length in males (**p = 0.002) but not in females (ns). There was also a sex-specific increase in the latency to feed in the NSF in htau males at 8 wks (**p = 0.0035) and 16 wks (****p < 0.0001), which may indicate anxiety.

In htau mice, 5-HT neurons co-expressing Vglut3 in the centromedial DRN exhibited altered expression of K+ and Na+ channel subunits Kcna4 (*****p < 0.0001) and Scn4b (**p = 0.0079). Ex vivo electrophysiological recordings confirmed increased excitability/reduced rheobase (**p = 0.0055) and current-dependent changes in AP kinetics (*p = 0.0492) in these neurons that aligned with gene expression patterns.

Conclusions: AD-related neuropathology in 5-HT DRN neurons recapitulates sleep and affective disturbances in early AD. 5-HT/Vglut3 neurons neurons in the DRN exhibited pathological changes that may drive prodromal NPS and promote tau spread to the cortex.

Disclosure: Nothing to disclose.

13.2 Linking locus coeruleus degeneration to slow-wave sleep in Alzheimer’s disease

Neus Falgas

Hospital Clínic de Barcelona, Barcelona, Spain

Background: Locus coeruleus (LC) degeneration, a hallmark of Alzheimer’s disease (AD), occurs early in the disease course, preceding cognitive deficits. This noradrenergic nucleus of the brainstem is linked to tau pathology accumulation within key nuclei regulating sleep and behavior, contributing to prodromal neuropsychiatric symptoms such as depression and sleep disturbances. Slow-wave activity (SWA) plays a crucial role in memory processing, both of which are impaired in AD. However, the relationship between LC degeneration and changes in slow-wave sleep remains unclear.

Methods: We recruited 58 participants diagnosed with AD based on cerebrospinal fluid (CSF) biomarkers (n = 54) or amyloid-PET (n = 4) at the Hospital Clínic de Barcelona. Participants underwent overnight video-polysomnography (PSG) and neuromelanin-sensitive MRI to assess LC integrity. CSF noradrenaline was measured using high-performance liquid chromatography. Sleep parameters, including power in the slow oscillation (SO, 0.5–1 Hz), delta (1–4 Hz), and SWA (0.5–4 Hz) frequency bands, were computed from deep non-rapid eye movement (NREM) sleep stages (N2 and N3) using PSG frontal electrodes (F3 and F4). Linear regression models evaluated the relationship between LC integrity or CSF noradrenaline and SWA, adjusting for age, sex, Clinical Dementia Rating (CDR), and prescribed medications.

Results: The sample had a mean age of 69 years, balanced by sex (50% women), and included participants in early AD stages (mild cognitive impairment or mild dementia) (Table 1). Twenty-four percent and 43% of participants were prescribed sleep and antidepressant medications, respectively. LC integrity was positively associated with SWA (β = 0.27, p = 0.043), independent of age, sex, CDR, and medications. Similar trends were observed for SO (β = 0.27, p = 0.059) and delta power (β = 0.25, p = 0.07). No significant association was found between SWA and CSF noradrenaline levels.

Conclusions: These findings suggest that LC integrity contributes to SWA alterations in AD, highlighting its potential role in the disruption of sleep-related neurophysiological processes. This study emphasizes the importance of LC degeneration in the sleep pathology of AD and supports further exploration of LC-targeted interventions to address sleep and cognitive deficits.

Disclosure: Nothing to disclose.

13.3 Gene expression in the mid-life human locus coeruleus across Alzheimer’s risk factors and neuromelanin content

Bernard Mulvey

Lieber Institute / Johns Hopkins University, Nashville, Tennessee, United States

Background: Two lifelong histopathologic processes occur in the noradrenergic locus coeruleus (LC): aggregation of Alzheimer’s disease (AD)-associated phosphorylated tau (pTau), and deposition of neuromelanin (NM). Importantly, LC NM begins to decline by age 65, around when early signs and symptoms of sporadic AD often emerge. In AD, the LC undergoes accelerated NM loss, and eventually, degeneration; moreover, MRI measurements suggest LC NM loss is prognostic for further cognitive decline. The transition of LC from dysfunction (depigmentation) to degeneration is concurrent with the spread of AD pathology and evolution of AD symptoms, suggesting a role of LC in pre-AD pathology and symptomatology. However, it remains unclear whether NM or general AD risk factors such as female sex, African ancestry, or the APOE4 genotype cause a molecular predisposition to pTau accumulation and/or AD in the human LC.

Methods: We obtained spatial transcriptomic profiles (10x Genomics Visium and Xenium) of postmortem human LC tissue from 30 middle-aged control brain donors with neither psychiatric disorders nor symptoms of neurodegenerative disease. Donors were balanced for sex, APOE2/4 genotype, and European/African ancestry.

Results: Gene expression clustering classified ~2,375 µm2 Visium ‘spots’ by their predominant cell types, such as astrocytes or LC neurons. Differential expression analyses of LC revealed proteostasis-related gene expression changes in APOE4 carriers. Quantitative NM measures from resulting high-res H and E images were used to modeled NM relationships, including for single LC neurons (Xenium), with gene expression, revealing LC NM content to be associated with expression of 1) genes involved in redox balance (GPX3) and autophagosome biogenesis (MAP1LC3B), and 2) genes regulated by proteostasis-associated transcription factors (e.g., ATF3).

Conclusions: These findings lend previously unavailable molecular contexts to the state of the aging human LC, and to NM as a promising biomarker for early/preclinical AD.

Disclosure: Nothing to disclose.

13.4 Compensatory locus coeruleus hyperactivity drives behavioral symptoms in prodromal Alzheimer's disease

Abstract Not Included

Panel

14. Digital Solutions for PTSD: Markers, Mechanisms, and Intervention Optimization

14.1 Passive screening for PTSD in primary care settings

Camilo Ruggero

University of Texas at Dallas, Richardson, Texas, United States

Background: Most mental health care in the US occurs in primary care settings, not psychiatric ones. Undetected PTSD is common in primary care with high downstream costs for individuals and society from the lack of detection and treatment. This places a tremendous burden on primary care providers to screen for PTSD, but time and resource constraints limit these opportunities. Screening for PTSD through use of AI-based passive monitoring of behavioral signatures in facial expressions, speech, language, and activity, hold promise for integration into primary care settings to assist providers, but the accuracy and validity of this screening remain unproven.

Methods: Primary care patients (N = 700) were video recorded as they spoke with their provider about lifestyle change to improve cardiometabolic health and then asked to wear a Fitbit to monitor their activity and sleep for 2 weeks. All patients were 9/11 responders and thus trauma-exposed (10.1% have current PTSD diagnosis), but present visits were unrelated to behavioral health. Features were extracted using state-of-the-art models from videos (language, speech, and facial expressions) and the 2-week Fitbit monitoring. Pre-registered models previously trained to predict PTSD checklist (PCL-5) scores were tested individually. Next, an ensemble model was trained using machine learning to predict PCL-5 using all modalities in 500 patients and tested in 200 held-out patients. We shared predictions of resulting model with providers, collecting systematic feedback.

Results: Performance of passive detection models reached as high as r = 0.42 for language congruence with PTSD checklist, but were modest for other passively detected markers including activity, sleep, speech, and facial expressions (r’s < 0.20). Integrating all modalities improved performance over any one and effects were independent of sex. Provider feedback supported feasibility and utility of implementation.

Conclusions: Passive detection of PTSD in primary care holds tremendous promise for bridging the resource gap faced in these settings. Results provide preliminary support for their use as an initial screening tool to signal a need for further evaluation. However, specialized training for the detection of PTSD remains important and results suggest AI-based passive monitoring cannot replace this need entirely.

Disclosure: Nothing to disclose.

14.2 Digital biomarkers as personalized predictive markers of accelerated aging, biomarkers of stress, neurocognitive performance and mental health

Katharina Schultebraucks

NYU Langone Medical Center, New York, New York, United States

Background: Traumatic experiences significantly increase the risk of mental disorders, impair neurocognitive performance, and affect biomarkers of stress. Traditional methods for assessing these risks rely on subjective self-reports, which are prone to biases. We propose a new digital phenotyping approach and large language models (LLMs) to identify objective digital biomarkers from video recordings. This approach aims to predict mental health and neurocognitive functioning, as well as to detect subtle differences in stress biomarkers and epigenetic markers of accelerated aging.

Methods: We enrolled 300 trauma survivors (age = 37.61 ± 12.90, 26.29%women) admitted to the Emergency Department (ED) within 24 hours of a traumatic event and meeting DSM-5 PTSD criterion A. In the ED we video-recorded unstructured trauma narratives. Using deep learning, we extracted digital biomarkers to develop a prognostic model for PTSD risk. Separately, we applied a zero-shot LLM to analyze trauma narrative transcripts alone, predicting PTSD diagnosis after trauma. Additionally, we enrolled 300 ED clinicians (age = 38.4 ± 10.6; 65.5%women) and video-recorded narratives about work-related stressors.

Results: Digital biomarkers from the ED accurately forecasted future PTSD diagnosis after trauma (AUC = .82, f1-score = .81). LLM analysis of trauma narratives predicted PTSD diagnosis with an AUC of 0.73, f1-score of 0.71, and sensitivity of 0.79. In addition, zero-shot LLM prompt engineering accurately predicted clinical phenotypes from work-related narratives (accuracy = 70.9%; F1-score = 71.8%; sensitivity = 77.1%). Digital biomarkers also accurately predicted biomarkers of stress, accelerated aging and neurocognitive functioning.

Conclusions: Digital biomarkers derived from naturalistic speech in clinical settings can risk-stratify mental disorders in real-world settings. This is the first study showing that deploying reliable, AI-driven tools for PTSD risk assessment in the ED can enhance patient care and enable early identification of at-risk individuals. Furthermore, we demonstrate the potential of digital biomarkers for assessing biomarkers of stress and mental health, marking a significant step towards unlocking the clinical potential of digital phenotyping and for revealing novel links between brain and behavior.

Disclosure: Nothing to disclose.

14.3 Elucidating personalized maintenance mechanisms of PTSD using smartphone sensors

Whitney Ringwald

University of Minnesota, Minneapolis, Minnesota, United States

Background: Available therapies for PTSD take a one-size-fits-all approach, but it is likely the disorder is maintained by different mechanisms for different people. Four key behavioral mechanisms theorized to maintain PTSD could be targeted with personalized treatment: sleep disruption, low physical activity, social disengagement, and avoidance. An ideal tool for assessing these behaviors are smartphone sensors. By unobtrusively monitoring patients in the flow of everyday life, sensor data can measure how these behavioral processes precipitate symptoms. The effects of behavior on PTSD symptom fluctuations can be personalized with dynamic modeling; however, no studies to date have done so.

Methods: I will present results of a study that explicated personalized markers of behavioral mechanisms that maintain PTSD. Data were drawn from a sample of 1000 trauma-exposed patients who completed a 90-day ambulatory assessment protocol involving smartphone sensor data collection and daily PTSD symptom ratings. Raw sensor data were aggregated at the daily level into the following variables: 1) minutes inactive at night (sleep duration); 2) step count (physical activity) from accelerometer; 3) phone unlock count (social engagement) from screen data; and 4) minutes at home (withdraw) from GPS. I used dynamic structural equation models (DSEMs) to extract person-specific behavior markers for maintenance mechanisms.

Results: On average, two within-person effects were significant, showing reduced physical activity (standardized beta = −0.11) and lower sleep duration (beta = −0.04) predict worsening symptoms for traumatized patients. Importantly, there was significant heterogeneity in all maintenance mechanisms, revealing substantial subgroups of patients with very strong effects of behavior on symptom change (betas >0.50). Results were robust to effects of sex.

Conclusions: We identified objective behavioral markers that can only be detected by smartphone sensors. As the first study to extract person-specific effects of sensed behavior on symptom changes, results showcase a new method of classifying patients based on modifiable behavioral mechanisms. I will discuss a potential path forward for translating these markers into tailored treatments for PTSD.

Disclosure: Nothing to disclose.

14.4 Leveraging digital biomarkers to predict treatment adherence in trauma survivors: insights from the two studies in emergency departments

Arieh Shalev

New York University Langone Medical Center, Beit Zait, Israel

Background: Early preventive interventions have been shown to be effective for high-risk trauma survivors, but only a minority seek help within the first critical months after the trauma. We sought to accurately identify trauma survivors at risk of treatment non-acceptance and non-adherence.

Methods: To identify high risk survivors seen in the Emergency Department (ED), we analyzed an ongoing observational study (PREDICT) and re-analyzed a previous RCT (J-TOPS). We applied advanced computational approaches to video- and audio-recorded narratives in the ED, integrating these with Electronic Health Records. PREDICT participants are 300 trauma survivors (38.1 years, 27.3% females) admitted to two Level-1 Trauma Centers, and J-TOPS participants are 957 consecutive admissions to ED (36.3 years, 54.1% females). All experienced a DSM-5 criterion A trauma.

Results: In PREDICT, only 6.6% sought help within the first 6 months. They were younger (36.1 ± 15.6 vs. 38.2 ± 13.5 years), more likely female (55.5% vs. 28.2%), and more likely suffered a physical trauma (45.5% vs. 15.6%). Across all follow-ups (1-, 3-, and 6-month), individuals who sought help consistently reported higher PTSD symptom severity (CAPS-5: 30.7 ± 4.16 vs 7.67 ± 2.52, PCL-5: 35.3 ± 6.81 vs. 11.67 ± 4.7). In J-TOPS, we found that only individuals in the Slow Remitting symptom trajectory responded to early interventions, with a growth factor parameter estimate of −0.96 (S.E. = 0.49, p < 0.05). In both studies, I will present early predictors, identified using advanced computational techniques, of major outcomes: (a) attended clinical assessments and subsequent CBT treatment within one month of trauma, (b) showed consistent treatment adherence, and (c) achieved good treatment outcome. Furthermore, I will present on whether digital biomarkers extracted from video-recorded trauma narratives in the ED can be used to forecast treatment adherence.

Conclusions: Data from ED and one-week assessment can provide valuable insights for identifying individuals at risk who would benefit from early interventions. These findings can guide individualized clinical decision-making in the ED, potentially improving outcomes for trauma survivors.

Disclosure: Nothing to disclose.

Mini Panel

15. Microglial Diversity Unveiled: Mapping Broad State Transitions, Species-Specific States, and Modulators of Lasting Immune Memory

15.1 CSF1R PET: delineating age-driven microglial shifts in early cognitive decline

Jennifer Coughlin

University of Texas Southwestern Medical Center, Dallas, Texas, United States

Background: Recent transcriptomic approaches using human brain tissue suggest a complex, spatial heterogeneity and shifting character of microglial populations across the course of Parkinson’s disease (PD) or Alzheimer's disease (AD). Aging is a modulator of microglial transcriptional states. Toward tracking broad shifts in regional abundance of microglia in aging and neurodegeneration, we use [11C]CPPC PET to image the colony stimulating factor 1 receptor (CSF1R). The CSF1R is key to microglial survival and proliferation, and is expressed chiefly by microglia within select areas of brain parenchyma. Using [11C]CPPC PET, we recently demonstrated that, relative to demographically-matched healthy controls, individuals with mild cognitive impairment (MCI) from early PD lacked the higher brain CSF1R that was found in those with moderate severity of PD. Guided by transcriptomic data, we use [11C]CPPC brain PET to test for a hypothesized, modest increase in CSF1R density with aging over the later decades of life that does not differ in amnestic MCI compared to cognitively intact (CI) individuals.

Methods: The study was approved by the Johns Hopkins IRB. Each participant provided written informed consent. The study enrolled adults who were a) between 45–80 years of age and b) assessed as CI or meeting Petersen criteria for amnestic MCI. Exclusion criteria consisted of nicotine use, substance use disorder, a non-MCI condition assessed as influencing cognitive performance, or contraindication to PET or MRI. A clinical interview, the Clinical Dementia Rating scale, neuropsychological testing, and laboratory values were used at screening. Each participant completed a brain MRI and a 90 minute [11C]CPPC PET scan. Partial volume correction (PVC) was applied to the PET data. [11C]CPPC binding (VT) in nine brain regions was estimated using Logan graphical analysis with a metabolite-corrected arterial input function. Composite VT was derived from the mean of regional VT values.

Results: Twenty-five CI individuals (11 females; age: range 47–80 years, mean ± SD = 64.5 ± 9.7 years) and seven individuals with amnestic MCI (1 female; age: range 47–80 years, mean ± SD = 71.9 ± 5.5 years) completed the study. Within the CI group, age correlated with composite [11C]CPPC VT (r = 0.61, P = 0.001), and with VT in each of the nine regions of interest. Within MCI, age correlated with composite [11C]CPPC VT (r = 0.76, P = 0.049). The groups (CI, MCI) did not differ in regional [11C]CPPC VT after accounting for age. There was no observed effect of sex on those findings. Use of VT values derived from PET data without PVC did not change the results.

Conclusions: These data support a rise in the CSF1R across multiple brain regions in aging after middle-age. After accounting for age, the CSF1R was not higher in MCI compared to CI individuals. The higher CSF1R with older age may reflect subtle proliferation of shifting microglial populations over aging, as suggested by some transcriptomic data.

Disclosure: D and D Pharmatech, Stock / Equity - Publicly Traded Company, Spouse/Partner

15.2 Spatial-omic methods to uncover novel inflammatory subsets of microglia in the brain

Rebecca Beiter

UMass Chan Medical School, Worcester, Massachusetts, United States

Background: Senescence is a physiological process, which has historically been associated with aging and an inability to undergo cell division. At the same time, senescent cells enter a chronic inflammatory state, which includes secretion of the senescence-associated secretory phenotype or SASP - a cocktail of secreted inflammatory mediators (cytokines, matrix metalloproteases, etc.) that impacts the function of surrounding cells. In addition to aging, recent evidence now implicates senescent cells in neurodegeneration in diseases such as Alzheimer’s Disease (AD) and Multiple Sclerosis. However, it remains to be determined where these senescent cells are localized in the brain during neurodegeneration and whether senescence influences the molecular phenotype of these cells.

Methods: We have used MERFISH (multiplexed error robust fluorescence in situ hybridization), an innovative spatial transcriptomic technique to measure the copy number and spatial distribution of 300 senescence-related genes directly in male and female human and mouse brain tissue. We are further using pharmacological strategies to inhibit specific factors secreted by senescent microglia to uncover novel mechanisms by which they contribute to AD-related phenotypes.

Results: We have identified that senescent cells are highest in AD-relevant neurodegeneration vs. normal aging or acute neuroinflammation in mice (n = 3 per condition). Further, of the cell types that have this senescent signature, microglia are the most pronounced and they are TREM2-dependent. We have since validated these findings in human AD tissue (n = 3 per condition) and shown that these senescent microglia increase with AD severity. In cultured cells, these senescent microglia are induced by amyloid beta and they secrete SASP factors. Finally, if we inhibit one of these SASP factors, CXCL3, it attenuates risk assessment behavioral defects in an AD-relevant mouse model (n = 8 per condition).

Conclusions: Senescent microglia are the pronounced senescent cell type in neurodegeneration in mouse and human brain. They are induced by activation of TREM2 and amyloid beta. Inhibition of a senescence factor secreted by microglia results in attenuation of AD-related behavioral defects in mice.

Disclosure: Nothing to disclose.

15.3 Prenatal immune stress leads to protection against age-related cognitive decline and microglia activation only in females

Lindsay Hayes

University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States

Background: A major hallmark of aging is cognitive decline and microglia activation. Numerous studies demonstrated that high levels of immune action in the brain is correlated with poor cognitive performance in aging in both human and mouse models. Interestingly, we found that maternal immune activation (MIA) induced a tolerized or blunted immune activation phenotype in microglia that was persistent from development into adulthood (Hayes et al. 2022). Therefore, we hypothesized that these tolerized microglia may be resilient against age-related immune activation. We now examine if offspring from MIA animals exhibit protection against age-related pathologies including cognitive decline and microglia activation.

Methods: Cognitive decline during aging was assessed in MIA and control (CON) offspring in adulthood (4 months) and aging (19–22 months) using Barnes maze and fear conditioning assays to assess spatial and contextual memory. Furthermore, locomotion and anxiety were assessed using the open field test. Behavior was performed on 38 young CON (18 female, 20 male), 38 young MIA (18 female, 20 male), 33 old CON (16 female, 17 male) and 34 old MIA (14 female, 20 male) offspring. Microglia immune activation was assessed using bulk cell and single-cell RNA sequencing and microglia morphometric analysis. Sequencing was performed on 4 mice per group and microglia morphology was performed on 20–30 cells per group (young CON, aged CON, young MIA, aged MIA). Data was analyzed using two-way ANOVA and linear regression analysis.

Results: We found that, with aging, female MIA offspring show resilience against cognitive decline in both the Barnes maze and trace fear conditioning tests in comparison to CON aging (p = 0.046, p = 0.004). In addition, we find the aged female MIA offspring have increased locomotor activity (p < 0.02) with no evidence of change in anxiety as measured by time in the center of an open arena (p > 0.05). Next, microglia from aged MIA offspring show a sex and age dependent morphologic change with female MIA microglia having a more ramified morphology in aging compared to CON (p < 0.046) and there was no effect in aged male microglia (p > 0.05). Microglia activation was evaluated by the lysosomal content that showed a pronounced increase with age (p < 0.001) and only a mild difference between MIA and CON microglia with aged MIA microglia showing a slight increase in lysosomal content. Finally, microglia sequencing data shows that aged MIA female microglia indeed have a reduction in the age-related increase in inflammation and a decrease in disease-associated microglia markers that is not found in male microglia.

Conclusions: In sum, we found that prenatal inflammation leads to a tolerization of microglia that is persistent into aging, particularly in females. Altogether, the data suggests that decreased age-related microglia activation may lead to a protection against cognitive decline in female MIA offspring. We are now exploring molecular mechanisms driving the female specific protection against aging pathologies in MIA offspring with a focus on the anti-inflammatory role of sex hormones in females. In sum, these data have implications for both aging and neuropsychiatric disorders that are linked to prenatal inflammation.

Disclosure: Nothing to disclose.

Study Group

16. The ‘Litmus Test’ for Biomarkers: Does Their Use in a Clinical Trial Lead to Better Outcomes for Patients?

Aristotle Voineskos, Anissa Abi Dargham, Ginger Nicol, Ishrat Husain, Benjamin Zebley, Katherine Burdick

University of Toronto, Toronto, Canada

Study Group Summary: Despite considerable investment, no biomarkers are regularly in use to help people with mental health and substance use problems. Yet, there may be opportunities to evaluate biomarkers in the clinic, and potentially change clinical practice and care. The time is now to conduct randomized controlled trials that directly assess the utility of promising biomarkers in ordinary clinical practice. Prediction of outcomes, events, or treatment response does not need to be perfect. It needs to be better than chance, to provide more benefit than harm, and, where possible, to be cost-effective.

The proposed Study Group will introduce four large multi-center clinical trials, either funded by the National Institute of Mental Health or Wellcome Trust which are currently in progress: all directly comparing the use of biomarker guided and informed treatment algorithms vs. usual care. Of note, these trials span much of the human lifespan from youth with early psychosis, to adults with depression, to elderly people with late-life treatment resistant depression. They also span different health care settings, from publicly insured systems, to private systems, and also from higher income countries (e.g. Canada, the U.S., the U.K.) to lower income countries (e.g. Pakistan, Nigeria). Biomarkers guiding treatment decisions in these studies range from a personalized side effect recommender plus pharmacogenetics, to multi-scale modeling incoporating symptom profile, imaging profile, and genetic profile, to presence or absence of discrete biomarkers such as functional genetic markers with high odds ratios for weight gain or agranulocytosis. Importantly these studies are designed to balance both improvements in treatment response outcomes and reductions in side effect outcomes.

The Study group will discuss (and debate) what may come next if some or all of these studies are successful. For instance, if the use of biomarkers to guide treatment decisions are shown to lead to better outcomes, how will they make it into clinical practice? How will neuroscientists, clinical trialists, and the psychiatric services field work together for successful implementation? Engaging patients and family members with lived experience will also be essential, and some of the studies that will be discussed are models of such engagement. Patients and families are incredible advocates for advances in care, and data show that they are interested in more objective feedback about diagnosis and treatment. Finally, engaging policy makers who may have a say in health system incentives early in the process, as well as the relevant regulatory agencies, will also be crucial for success. All of these strategies to 'set the stage' for successful implementation, will be an essential focus of discussion and debate.

Disclosure: Nothing to disclose.

Mini Panel

17. If the Brain is Immune Privileged, Then What are Immune Cells Doing in the Brains of People With Schizophrenia and is This Related to a Leakier BBB?

17.1 Inflammation at the gate: physical evidence of immune cell transmigration and brain blood vessel pathology in schizophrenia

Cyndi Weickert

Upstate Medical University, Clay, New York, United States

Background: In schizophrenia brain, increased macrophage transcript, CD163, is the most robust transcriptional change detected by RNAseq and pathway analysis identified increased diapedesis or immune cell transmigration. Thus, we hypothesized that molecular and cellular changes consistent with a breakdown of the blood-brain barrier (BBB) would be found in the brains of people with schizophrenia.

Methods: We studied over 200 post-mortem human brains (~90 schizophrenia and ~120 controls) from three brain banks SMRI, TRC and NIMH. We determined inflammation status by measuring cytokines and performing clustering analysis (those with high inflammation are termed neuroinflammatory). Fresh frozen (14μm) coronal sections from prefrontal cortex, midbrain and caudate were generated on a cryostat followed by immunohistochemistry. We measured mRNA levels by RT-PCR from total RNA isolated using Trizol and measured proteins using ELISAs. We isolated single nuclei using 10x Genomics kits, made cDNA libraries and performed sequencing on Novaseq 6000. We performed filtering of low-quality nuclei and doublets, normalization, and data scaling. We identified 33 transcriptionally distinct cell populations. We focused on immune cells and BBB cells to determine proportional shifts and differential gene expression analysis between diagnostic groups. We applied t-tests, ANOVAs, ANCOVAs, chi-square, and snRNA seq analysis approaches to test for diagnostic and inflammation subgroup differences. Both male and female brain were used with an approximate 60% male/40% female split.

Results: Robust increases in our macrophage marker, CD163 mRNA (F = 41.35, p < 0.0001), and increases in levels of an ECM protease, MMP9, mRNA (F = 24.45, p < 0.0001) were found. These changes were accompanied by increases in immune cell chemoattractant (CCL2) and angiogenic factors SERPINE1 [mRNAs (both p < 0.001) and proteins (both p < 0.05)]. We discovered blood vessels showing fragmented pathology in 75% of people with neuroinflammatory schizophrenia and only 19% of controls (χ2(4) = 19.65, p < 0.0001). Using snRNA, we generated over a billion reads/500,000 nuclei and found increased CD163+ macrophages. We identified many T cells (CD3+, CD4+ and CD8+) in brain homogenates and in tissue. We found that macrophages were pro-inflammatory with increased MHC (Log2 fold change12.96, p < 0.0001) and evidence of activated T cells (increased CD8 and CD28 mRNAs, p < 0.01). We found an 80% increase in endothelial cell proportion (Coef = 0.7, p.adj = 0.025) and changes consistent with endothelial cell damage in schizophrenia brain.

Conclusions: We find more activated and inflammatory immune cells in the brains of people with schizophrenia. Increased transcripts important in cellular communication between the innate and adaptive immune system suggest that both classes of immune cells are actively recruited to schizophrenia brain. We discovered morphological and molecular changes consistent with destruction of small blood vessels, implicating a leakier BBB and increased angiogenesis in people with schizophrenia.

Further, we have evidence that these peripheral immune cells appear to be responding and presenting antigens from the schizophrenia brain.

Disclosure: Nothing to disclose.

17.2 Peripheral markers of blood brain barrier disruption and immune cell transmigration are related to mesial temporal lobe cortical thickness reductions and are reduced with canakinumab in neuroinflammatory schizophrenia

Thomas Weickert

State University of New York Upstate Medical University, Syracuse, New York, United States

Background: Inflammation is linked to schizophrenia pathophysiology and increased CD163+ macrophages are found in multiple brain regions in schizophrenia. Immune cell transmigration into human brain involves blood brain barrier (BBB) disruption resulting in increased Vascular Endothelial Growth Factor (VEGF), matrix metalloproteinase-9 (MMP9), and CD163. Thus, we predicted that soluble CD163 (sCD163) and VEGF would be increased in peripheral serum of people with schizophrenia especially in those with other markers of increased inflammation. We also expected serum levels of VEGF and/or sCD163 would inversely correlate with brain cortical thickness and that treatment with a monoclonal antibody to reduce inflammation would reduce elevated CD163, MMP9 and VEGF.

Methods: Serum samples were obtained from the Australian Schizophrenia Research Bank (n = 1,143, males = 581, females = 562) and VEGF, sCD163 and CRP proteins were measured by ELISA in 499 people with schizophrenia or schizoaffective disorder and 644 healthy controls. All individuals were classified as normal (<3 µg/ml) or elevated CRP levels (>3 µg/ml). Structural 1.5T MRIs (n = 280) were used to determine cortical thickness via FreeSurfer. Diagnostic X inflammatory subgroup differences were determined by ANOVA. ELISA data for CD163, MMP9 and VEGF from peripheral blood were analyzed in an independent sample of 29 patients with schizophrenia or schizoaffective disorder who were part of a randomized, double-blind, placebo control trial of canakinumab which blocks Interleukin 1beta binding in which planned t-tests were used to compare these BBB integrity markers after 4 and 8 weeks of treatment to baseline levels.

Results: Schizophrenia patients had elevated sCD163 t(1085) = 4.32, p < 0.0001, and VEGF levels t(1082) = 4.51, p < 0.0001, Cohen's D = 0.31, relative to healthy controls. There were significant differences in sCD163 and VEGF (both F's > 13.00, p's < 0.00001) based on inflammation subgroups. The elevated inflammation schizophrenia subgroup displayed higher VEGF and sCD163 levels than healthy control subgroups (all p’s < 0.0001). sCD163, but not VEGF, correlated positively with age and duration of illness (p < 0.01 and p < 0.02 respectively). VEGF levels were inversely correlated with parahippocampal gyrus cortical thickness (r = −0.40, p < 0.01, Cohen's D = 0.83, power > 0.90) in neuroinflammatory schizophrenia. There were significant reductions from baseline of sCD163, t(12) = 1.9, p = 0.04, MMP9, t(10) = 2.8, p = 0.02, and VEGF, t(12) = 2.9, p = .006, (Cohen’s D's = 0.40) in patients receiving canakinumab but not in patients receiving placebo.

Conclusions: Serum proteins indicative of BBB changes and macrophage migration are increased in neuroinflammatory schizophrenia. These changes do not appear to resolve but may worsen with time and relate to brain tissue damage of the mesial temporal lobe. Further, a treatment blocking inflammation reduced peripheral levels of immune cell transmigration markers in patients with schizophrenia.

Disclosure: Nothing to disclose.

17.3 Beyond barriers: blood-brain barrier leakage in schizophrenia spectrum disorders revealed by DCE-MRI

Joanna Moussiopoulou

LMU University Hospital, LMU Munich, Germany, Munich, Germany

Background: Our previous study reported increased blood-brain barrier (BBB) leakage in schizophrenia-spectrum disorders (SSDs) compared to healthy controls (HCs), using dynamic contrast-enhanced MRI (DCE-MRI) in the largest cohort to date (41 SSD, 40 HC). Replication is needed, and underlying mechanisms remain unclear. This study aimed to replicate these findings and explore potential mechanisms using a transcriptomic approach.

Methods: We conducted a cross-sectional study including 82 individuals with SSD (both sexes, 41 newly recruited, 41 from the original cohort) and 52 age- and sex-matched HCs (both sexes, 40 from the original cohort). BBB permeability was assessed with DCE-MRI using the volume transfer constant Ktrans. Group differences in Ktrans were examined with voxel-wise ANCOVA in both the replication and full samples. To investigate genetic underpinnings, we performed imaging transcriptomics using the abagen and pyGSEA Python toolboxes. We computed spatial Spearman correlations between unthresholded Ktrans maps and gene expression data from the Allen Human Brain Atlas across Brainnetome atlas regions. These correlations (~15,000 genes) were input for gene set enrichment analysis (GSEA) to test for enrichment of cell types implicated in BBB function and SSD.

Results: SSD patients showed significantly increased BBB leakage compared to HCs (p < 0.001, FWE-corrected at α = 0.05). In the replication sample, 6,894 affected voxels overlapped by 28.3% with those from the original cohort. Combined analysis revealed 4,412 significant voxels, largely subcortical (e.g., thalamus, hippocampus, amygdala, brainstem). A small subgroup (9 %) drove the effect. Imaging transcriptomics with GSEA revealed significant enrichment (q < 0.05) of glial cell types, particularly astrocytes and microglia.

Conclusions: This study, confirms BBB dysfunction in the largest SSDs cohort to date and is the first to link this with regional gene expression profiles. The findings suggest that glial cell dysfunction and neuroinflammatory processes—particularly involving astrocytes and microglia—may be associated with BBB breakdown in SSD. Further research is needed to elucidate the mechanisms and clinical implications of these findings.

Disclosure: Nothing to disclose.

Panel

18. Molecular and Functional Characterization of Opioid Hotspots in Brain Reward Circuits Across Species

18.1 Spatiomolecular characterization of transcriptionally distinct DRD1-expressing islands in the human NAc

Robert Phillips

Lieber Institute for Brain Development, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States

Background: The nucleus accumbens (NAc) is a GABAergic midbrain structure that is dysregulated in a variety of neuropsychiatric diseases, including substance use disorders and schizophrenia. Recent studies have used single nucleus RNA-sequencing (snRNA-seq) and spatial transcriptomics to identify distinct cell types that control specific behaviors. These studies identified a novel cell type with high expression of dopamine receptor D1 (DRD1) and mu-opioid receptor (OPRM1), organized into circular clusters known as D1-islands, which regulates components of drug-induced behaviors. However, no such spatial transcriptomics data exists for the human brain. Understanding the spatial topography of transcriptionally distinct cell types within the human NAc is essential for translating findings from animal studies and for understanding the spatiomolecular architecture of reward circuitry.

Methods: A 100 gene panel was used to generate Xenium spatial transcriptomics data from 20 tissue sections ~500 microns apart across the anterior-posterior (AP) axis of the NAc from two donors (1M/1F). Spatial clustering was performed with Banksy and a 3D reconstruction of the human NAc was performed using STAligner. Topography of identified cell types was validated using in situ hybridization in an independent donor.

Results: Spatial transcriptomics of the human NAc across the AP axis identified transcriptionally heterogenous neuronal cell types, including DRD1- and DRD2-expressing medium spiny neurons present along the AP axis of the human NAc. We identified two populations of transcriptionally distinct D1-islands that are differentially abundant along the AP axis, exhibit high expression of RXFP1, DRD1, and OPRM1, and differ based on expression of genes such as CPNE4. Cross-species analyses also identified that these populations are highly conserved across rodents, non-human primates, and humans. Our panel also included genes from opioid use disorder and schizophrenia GWAS, allowing us to identify the cell types and spatial domains that exhibit high expression of risk genes.

Conclusions: Cellular resolution spatial transcriptomics successfully mapped the spatiomolecular architecture of the human NAc across the AP axis, providing the ability to probe expression of disease risk genes and translate findings from rodent studies.

Disclosure: Nothing to disclose.

18.2 Spatial and transcriptional characterization of a μ-opioid receptor-enriched D1 medium spiny neuron population in the nucleus accumbens shell

Olivia Drake

The University of Alabama at Birmingham, Birmingham, Alabama, United States

Background: Opioid use disorder remains difficult to treat due to limited therapies targeting the neural substrates of opioid motivation. Opioids act via mu opioid receptors (μORs) to modulate mesolimbic dopamine circuits, and signaling in the nucleus accumbens (NAc) is central to opioid reward. Recent transcriptomic studies reveal that μOR (Oprm1) expression is unevenly distributed among subpopulations of medium spiny neurons (MSNs), but the identity and contributions of these distinct Oprm1-expressing neurons to opioid behaviors remain poorly defined.

Methods: Publicly available transcriptomic datasets from mice and rats were analyzed to identify Oprm1-expressing MSN populations. To assess spatial localization and gene expression changes following opioid exposure, we used 10x Genomics Xenium spatial transcriptomics after voluntary heroin self-administration and naloxone-precipitated withdrawal in male and female C57BL/6 mice (n = 8/group). Cell type identity was assigned using canonical marker genes and validated via Allen Institute’s MapMyCells tool.

Results: Analysis of published rodent data revealed a unique NAc shell dopamine receptor one (Drd1)-expressing MSN subtype expressing high levels of Oprm1 and marked by Chst9 (encoding carbohydrate sulfotransferase 9). This population also expresses Tshz1 and Tac3 (the rat ortholog of Tac2 in mice), genes linked with striatal cell types involved in reward and aversion. Xenium analysis of coronal mouse brain sections identified 36 transcriptionally defined cell types, including 23 neuronal populations. Of five distinct MSN subtypes, one corresponds to the Oprm1-enriched, Drd1+, Chst9+ population concentrated in islands in the medial and ventral NAc shell. Ongoing analyses aim to determine how heroin and withdrawal alter gene expression in this population. To enable functional studies, we have generated a Chst9-Cre-tdTomato transgenic rat for cell-type-specific manipulation, including CRISPR-based interrogation of Oprm1.

Conclusions: These findings confirm a transcriptionally and spatially defined subpopulation of Oprm1-enriched MSNs. Planned studies will investigate this population’s relevance to opioid-related behaviors. This work provides new insight into the cell-type-specific mechanisms of opioid reinforcement and may reveal novel treatment targets for OUD.

Disclosure: Nothing to disclose.

18.3 Dynorphin and reward seeking in the dorsal nucleus accumbens shell in a mouse model

Ream Al-Hasani

Center for Clinical Pharmacology, Washington University in St. Louis, St. Louis, Missouri, United States

Background: It has been well-established that the kappa opioid system modulates negative affective states. However, we previously showed for the first time that photo stimulation of dynorphin cells in the dorsal nucleus accumbens shell (dNAcSh) drives reinforcement-like behavior, as compared to the ventral NAcSh which drives aversion, as predicted. Since this discovery we have been working towards better understanding the function of this localized, non-canonical reward-like phenotype of dynorphin in the dNAcSh.

Methods: For all expts: preprodynorphin-Cre mice were injected with either AAV-DIO-ChR2-eYFP or AAV-DIO-eYFP virus into the dNAcSh for 30 days.

Sucrose self-admin: Mice underwent fixed ratio 1 (FR1) training in daily 1-hour sessions. On test day mice received an FR1 session plus 20 Hz stimulation.

Food-restriction: As above but mice were food restricted overnight, receiving only 2g of food.

Fentanyl self-admin: Mice were trained to self administer fentanyl in a two-bottle choice assay. During a test session mice received saline or DCZ (DREADD ligand) prior to water and fentanyl. During extinction training mice received 2 sippers containing water. During the reinstatement test mice were given saline or DCZ prior to fentanyl and water.

Social Interaction: Test mouse explored an arena containing 2 mesh-wired cups to habituate. The same procedure was repeated with a stranger mouse in the mesh-wired cups plus 20Hz stimulation. Time spent in a defined zone were scored using ethovision XT.

Results: Activation of dNAcSh dynorphin neurons significantly decreased operant responding for sucrose pellets/pellets consumed compared to baseline in male and female mice.

Following food restriction mice typically increase number of nose pokes/pellets consumed. However, activation of dNAcSh dynorphin neurons in food restricted mice did not show an increase in nosepokes/pellet consumption.

Chemogenetic activation of dNAcSh dynorphin neurons significantly decreased fentanyl consumption/preference compared to controls. Photostimulation of dNAcSh dynorphin neurons significantly decreased interaction time as compared to no stim.

Conclusions: Overall, activation of dynorphin cells in the dNAcSh blocks a number of rewarding behaviors. We believe this may be due to mice being in a heightened reward state, which we are investigating further.

Disclosure: Nothing to disclose.

18.4 Functional and transcriptomic adaptations in the ventral pallidum drive opioid intake despite negative consequences

Meaghan Creed

Washington University School of Medicine, St. Louis, Missouri, United States

Background: Most individuals can use prescription opioids such as oxycodone (OXY) as prescribed, while only a subset (~20–30%) continue intake despite negative consequences, a hallmark of OUD. The chronicity of OUD is driven by adaptations in the ventral basal ganglia. While prior work has mostly focused on the ventral tegmental area (VTA) neurons and their downstream target; the nucleus accumbens (NAc), the ventral pallidum (VP) is reciprocally connected with both NAc and VTA, and its activity is necessary for drug self-administration, sensitization and reinstatement. Yet little is known about how opioids induce plasticity in the VP, and how these changes drive OUD.

Methods: snRNA-Seq: Mice (60) self-administered OXY (12 days) prior to introducing air-puff paired to drug intake; following classification as punishment sensitive (PS) or resistant (PR), the VP was collected and cDNA libraries from individuals were sequenced (10X Genomics 3’ V3.1).

Patch clamp: We measured excitability, opioid sensitivity and synaptic output (16–32 cells/group) of candidate clusters following OXY-SA. Synaptic output was measured by transfecting neurons with channelrhodopsin, and measuring the PPR and asynchronous EPSCs.

Function: We altered opioid sensitivity (CRISPR-editing oprm1) and activity (synaptic silencing with Tet-Tox and increased excitability with NaChBac) to establish causality between cluster function and PR OXY intake (8–15 mice/group).

Results: Mice segregated into punishment-resistant (PS, 49/60) and punishment-resistant (PR, 12/60) pheontypes based on extinction in response to punishment; based on OXY-induced transcriptional changes, we prioritized the lypd1_chst9, slc17a6_masp and slc17a6_trp3 clusters for follow up.

slc17a6 clusters exhibited reduced excitability and reduced excitatory drive following OXY self-administration, and their activity and opioid sensitivity was necessary for PR OXY intake.

Conclusions: PR OXY intake emerges only after chronic self-administration, suggesting OXY-induced plasticity as a contributing factor. The Slc17a6-Masp1 neuronal cluster expressed the largest number of differentially-expressed genes, exhibit concomitant functional adaptations, and silencing their activity rendered all mice PR, establishing Slc17a6-Masp1 VP neurons as critical regulators of PR OXY self-administration.

Disclosure: Nothing to disclose.

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19. New Vistas on Interactions of GABAergic and Glutamatergic Inputs to Midbrain Dopamine Neurons: Implications for Addiction

19.1 Pallido-tegmental endocannabinoids actuate dopamine-based action selection

Joseph Cheer

University of Maryland School of Medicine, Baltimore, Maryland, United States

Background: Proactive behavioral control over threat-predictive stimuli allows individuals to avoid aversive events and maximize environmental fitting by diminishing generic threat responses (i.e., freezing). This learning process relies on phasic dopamine signals in the mesolimbic system that encode the association between threat-predictive stimuli and aversive outcomes. In previous research using appetitive learning tasks, we demonstrated that these associations are critically dependent on endocannabinoid (eCB) signaling within the ventral tegmental area (VTA).

Methods: In this study, we explore how the eCB system modulates dopamine signaling in scenarios involving negative reinforcement. We use viral-genetic tools to selectively delete the enzyme diacylglycerol lipase alpha (DGLa) in VTA dopamine neurons, which impairs the synthesis of the eCB 2-arachidonoylglycerol (2-AG) from these cells. We similarly excise, via cre-lox recombination, cannabinoid receptor type 1 (CB1) from ventral pallidum inhibitory afferents to dopamine dendrites. Next, we use fiber photometry to measure phasic dopamine release (GrabDA) in the nucleus accumbens (NAc) and eCB release (GrabeCB2.0) in the VTA during operant active avoidance.

Results: Our findings reveal that midbrain dopamine neurons require 2-AG mobilization to shape NAc dopamine release events that are predictive of active avoidance learning. Deletion of DGLα in VTA dopamine neurons disrupts active avoidance performance but does not affect unconditioned escape behaviors. We also find that VTA dopamine neurons release 2-AG in response to foot-shock presentations. To identify the presynaptic target of this 2-AG retrograde signal, we delete cannabinoid receptor type 1 (CB1R) in ventral pallidum (VP) terminals that project to the VTA. We show that this manipulation mimics the effects of DGLa deletion on NAc dopamine signals and active avoidance learning.

Conclusions: These results uncover a novel VTATH → VPCB1 2-AG message sculpting NAc dopamine release events and therefore orchestrating active avoidance learning. This mechanism may have implications for developing new treatments for anxiety disorders by enhancing proactive coping strategies.

Disclosure: Nothing to disclose.

19.2 Fentanyl distorts processing of natural rewards and aversive stimuli via opposing effects on phasic dopamine responses to predictive cues

Thomas Jhou

University of Maryland School of Medicine, Baltimore, Maryland, United States

Background: Mu opioid receptor (MOR) agonists produce rewarding and addictive effects by inhibiting GABAergic inputs to midbrain dopamine (DA) neurons, thereby increasing tonic DA. However, MOR agonists also distort processing of natural rewards and aversion-related stimuli, e.g. by reducing the value of natural rewards, and blunting the negative affect of unpleasant stimuli, also leading to increased drug use. These distortions are not well understood, but may involve phasic DA responses to these stimuli, but again, little is known about how these are influenced by MOR agonists.

Methods: We performed fiber photometry in C57BL/6J mice that received AAV expressing the fluorescent DA sensor GRAB-DA1m, along with optical fibers, into the nucleus accumbens (NAc) core or shell. Recording sessions consisted of 50–75 Pavlovian trials in which distinct auditory cues were followed 3 seconds later by either liquid sucrose, footshock, or no outcome (randomly interleaved trial types). Sessions were preceded immediately by a single acute injection of either saline or fentanyl (0.1mg/kg or 0.2mg/kg sc). In a separate group of mice, we measured glutamatergic signaling onto DA neurons using a cre-dependent fluorescent glutamate sensor iGluSnFR.A184S injected into the VTA of Dat-cre mice.

Results: Relative to saline, acute fentanyl dose-dependently reduced phasic dopamine activations to sucrose cues, while also reducing anticipatory licking responses to these cues, even as overall locomotion slightly increased. iGluSnFR signals at VTA DA soma also showed phasic excitations to sucrose cues, which were again abolished by fentanyl, showing that opioids inhibit excitatory reward-related DA neuron inputs. In contrast, fentanyl increased phasic dopamine responses to cues predicting footshock, and/or caused a shift from inhibition to excitation, consistent with opioid-induced loss of GABAergic phasic aversion-related input. Fentanyl also reduced freezing responses to shock cues.

Conclusions: MOR agonists distort reward-related and aversion-related DA phasic responses, likely through distinct effects on glutamatergic and GABAergic inputs that are anatomically (and possibly pharmacologically) separable. These results suggest mu opioid agonists targeting these distinct afferents might differentially alter reward- and aversion-related behaviors.

Disclosure: Nothing to disclose.

19.3 Validation of SOX14 as a selective marker of gabaergic neurons in mouse tVTA: towards the dissection of inhibitory inputs to midbrain dopaminergic neurons

Jennifer Kaufling

CNRS INCI, Strasbourg, France

Background: At the beginning of this century, a brain structure exerting strong tonic inhibition on dopamine neurons was identified and named the “tail of the VTA” (tVTA) or “rostromedial tegmental nucleus” (RMTg), due to its caudal position relative to the VTA and its extension into the pons. Prior work then elucidated tVTA roles in motor control, addiction, and aversion. However, functional studies in mice have been limited by the absence of selective molecular markers. We recently identified the transcription factor SOX14 as a selective marker of mouse tVTA neurons and characterized their cellular identity, anatomical boundaries, and connectivity. We also validated SOX14-IRES-Cre mice as the first genetic model allowing selective tVTA manipulation.

Methods: Histological analyses combined RNAscope and immunohistochemistry. To examine tVTA behavioural function we performed optogenetic Real-Time Place Aversion (RTPA). Male SOX14-IRES-Cre mice (n = 8) received AAV5-FLEX-ChrimsonR injections in the tVTA or control virus (n = 8) and while wild-type males (n = 9) received AAV5-ChrimsonR in the LHb. tVTA light illumination (635 nm, 5 ms, 60 Hz) was paired with one chamber for 15 min/day over 3 days, following a habituation session. Time spent and immobility were recorded.

Results: SOX14 positive neurons colocalized with GABAergic and mu opioid receptor-expressing tVTA neurons, but not with dopaminergic or serotonergic populations. Optogenetic stimulation of LHb terminals in the tVTA significantly reduced time spent in the paired chamber across 3 days (p < 0.001 vs habituation), indicating aversion. In contrast, global stimulation of tVTA SOX14+ neurons increased immobility on the first day (p < 0.001 vs habituation) followed by delayed aversion on days 2 and 3 (p < 0.01 vs habituation).

Conclusions: These results suggest functional heterogeneity within tVTA subpopulations. We hypothesize that the LHb–tVTA–VTA circuit mediates aversion, while the tVTA–SNc pathway contributes to motor suppression. Their combined recruitment may underlie the observed temporal dissociation between immobility and aversion, leading to locomotor inhibition followed by delayed aversion.

Disclosure: Nothing to disclose.

19.4 Mu opioid receptors couple to different G proteins in GABA and glutamate terminals Onto VTA neurons

Elyssa Margolis

UCSF, San Francisco, California, United States

Background: Mu opioid receptor (MOR) activation in the ventral tegmental area (VTA) is rewarding, and likely contributes to opioid use disorder. It is generally thought that the key MOR function in the VTA is presynaptic inhibition of GABA release to disinhibit dopamine neuron activity. Yet, seemingly paradoxically, MOR activation also inhibits glutamate release onto VTA neurons. However, it is not known whether MOR inhibition of GABA and glutamate afferents use the same intracellular signaling pathways. This raises the possibility that MOR mediated inhibition of neurotransmitter release at these VTA terminals is mediated by alternative signaling. If MOR coupling differs in VTA GABA and glutamate terminals then ligands might preferentially activate the receptor complexes on one type of terminal compared to the other.

Methods: We performed ex vivo whole cell voltage clamp recordings in VTA neurons from adult male SD rats. Electrically evoked GABA and glutamate synaptic currents (I/EPSCs) were pharmacologically isolated. Slices were incubated in 100 ng/mL pertussis toxin (PTX) for > 4 hr and myristoylated Gα blockers (1 uM) for > 1 hr.

Results: Consistent with prior work, DAMGO inhibited the amplitude of electrically evoked GABAAR mediated IPSCs to 30 ± 4% (n = 14) of baseline (Emax) with an EC50 of approximately 200 nM. Surprisingly, there was no impact on the DAMGO response in VTA slices incubated in PTX to block Gαi and Gαo signaling (26 ± 11% of baseline, n = 4; t = 0.3, p = 0.8). Yet DAMGO induced inhibition of electrically evoked glutamatergic EPSCs was diminished by PTX pretreatment (in PTX 73 ± 6% (n = 6) vs ctrl 55 ± 6% (n = 7); t = −2.2, p = 0.05). PTX is slow to act and does not block Gαz, a member of the Gαi/o family. Therefore we designed and validated myristoylated blockers for Gαi1, Gαi3, Gαo, Gαz, and Gαq for improved membrane penetration and Gα coverage. Gαi1/i3/o blockers diminished DAMGO inhibition of EPSCs (93 ± 11% of baseline, n = 5; t = −5.0, p = 0.0005). The Gαz inhibitor decreased DAMGO inhibition of evoked IPSCs (51 ± 8%, n = 11, vs interleaved controls 19 ± 6%, n = 4; t = 3.1, p = 0.009).

Conclusions: The differential signaling organization discovered here may enable functional selectivity of endogenous opioid peptides preferring one or the other of these two structural sites within the VTA (Gomes et al., 2020). Such selectivity may also be harnessed in future drug discovery.

Disclosure: Neumora Therapeutics, Consultant, Self

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20. Beyond the Static Brain: Clinical Relevance of fMRI Temporal Dynamics

20.1 Transient network functioning: methods, validation, and application to depression

Roselinde Kaiser

University of Colorado Boulder, Boulder, Colorado, United States

Background: Large-scale functional brain networks show dynamic (changing over time) properties. Understanding dynamic properties can provide insight into cognitive processes that correspond with external (cue-related) or internal (cue-unrelated or resting-state) events. Aberrations in dynamic properties and related cognitive processes may be especially relevant for mood disorders: people with or at risk for depression report intrusive, “sticky” introspective thoughts and difficulty sustaining attention to external goals. The present study tested and validated methods for evaluating dynamic network properties, and applied methods to evaluate risk for future depression.

Methods: Functional magnetic resonance imaging and behavior were collected during a working-memory task in n = 154 adolescents ages 13–19. Depressive symptom severity was evaluated quarterly for two years. Co-activation pattern analysis identified transient network states using k-means clustering and test-retest reliability analyses. A smoothing function was applied to the probabilistic time course of each state and state labels assigned based on the smoothed distance metric. Validation analyses tested the associations between transient network functioning and task events or behavior. Predictive analyses used dynamic structural equation modeling to model depressive symptom trajectories over two years, and associations between individual differences in dynamic network functioning and future depression.

Results: Results identified eight network states. Transient network functioning corresponded with condition type, X2(7) = 2442, p < 0.001, and block onset, X2(7) = 3228, p < 0.001, and predicted slower RT, X2(7) = 28.12, p < 0.001, and errors, X2(7) = 63.21, p < 0.001. Persistence of networks involving frontoparietal, B = 0.216, p = 0.010, 95% CI [0.050, 0.355], or midline regions, B = 0.196, p = 0.030, 95% CI [0.015, 0.353], predicted higher variance in future depression. Behavioral deficits also predicted depression variance, B = −0.167, p = 0.006, 95% CI [−0.281, −0.047], an effect partially mediated by frontoparietal network persistence.

Conclusions: Findings support methods for investigating transient networks and their dynamic properties, and suggest that aberrant dynamics of frontoparietal regions may be a marker of depression risk.

Disclosure: Nothing to disclose.

20.2 Methodological considerations for the use of brain signal variability in psychiatric neuroimaging

Lucina Uddin

University of California Los Angeles, Los Angeles, California, United States

Background: A burgeoning neuroscience literature reveals that temporal variability of neural responses constitutes an important and clinically-relevant signal. Brain signal variability (BSV) as measured using fMRI is a robust marker of lifespan neurodevelopment. Younger adults demonstrate higher BSV than older adults, and cognitive decline accompanies brain-wide loss of BSV in old age. We have shown that BSV is linked to symptom severity in children diagnosed with ADHD and autism. Still, lack of methodological standardization creates barriers to interpreting findings from the BSV literature.

Methods: We investigated several aspects of BSV in resting-state fMRI data. First, we assessed how different data analytic approaches (z-score normalized time-series vs. percent-change normalized time-series) influence relationships between BSV metrics. Second, we quantified the test-retest reliability of BSV metrics across four 15-minute resting-state scans. Finally, we used a multivariate analysis technique to characterize the relationship of BSV metrics with behavioral tests of executive function. Data from 416 subjects (mean age = 28.59 (3.71); 22–36 years old; 216 female) from the Human Connectome Project were analyzed using three BSV metrics: standard deviation (SD), mean square successive difference (MSSD), and sample entropy (SampEn).

Results: Average within-subject correlations of whole-brain voxel-wise BSV measures across all subjects were high (between 0.87 and 0.99), and were influenced by the time-series normalization procedure. SD, MSSD, and SampEn showed high test-retest reliability (intraclass correlation coefficients, ICCs between 0.5 and 0.9) in gray matter voxels across all four scan sessions. ICC’s were higher in gray matter for percent-change normalization than z-score normalization. All BSV measures showed similar relationships to behavioral measures of executive function that depended on whether percent change normalization or z-score normalization was applied.

Conclusions: We quantify how the normalization of the fMRI time-series influences the association between resting-state BSV measures, their test-retest reliability, and their relationship to cognitive performance. These findings underscore the importance of methodological choices in producing reliable BSV findings for clinical applications.

Disclosure: Nothing to disclose.

20.3 Non-neuronal bold signals as both a confound and a sensitive probe of cerebral hemodynamics and autonomic nervous system function

Blaise Frederick

Harvard Medical School, McLean Hospital Brain Imaging Center, Belmont, Massachusetts, United States

Background: Non-neuronal systemic low frequency oscillations (sLFO) in fMRI data are a major confound, causing widespread spurious “connectivity” unless addressed. Various methods have been developed to remove non-neuronal signals, but many, such as global signal regression, have major pitfalls. Our discovery that the sLFO signal moves with the blood led to the development of the Regressor Interpolation at Progressive Time Delays (RIPTiDe) method, which cleanly separates the sLFO from neuronal activation, without causing negative correlations, while simultaneously characterizing blood flow throughout the brain. Recent work shows that the global mean signal (GMS) (which is generated by the sLFO) is correlated with several peripheral physiological signals that reflect autonomic nervous system (ANS) function, specifically arousal. We therefore propose using the sLFO “noise”, extracted from the fMRI data, as a probe ANS function.

Methods: To separate the neuronal and system physiological portions of the BOLD signal, we used the “rapditide” open source package to perform retrospective RIPTiDe analyses on several existing datasets (a sample collected at McLean Hospital, the HCP-YA, the Midnight Scan Club dataset (OpenNeuro ds000224), an EEG/fMRI sleep study (OpenNeuro ds003768) and a simultaneous fMRI/pupilometry study (OpenNeuro ds003673). This allowed us to consider the two neuronal and sLFO signals independently.

Results: sLFO amplitude increases as arousal decreases, which frequently occurs over the course of an fMRI exam. We found consistent increases in sLFO amplitude within and between resting and task scans in all tested data sets. For example, over the first 15 minute HCP rs-fMRI scan, sLFO variance approximately doubled, and brain-wide functional connectivity (FC) increased by 71%. RIPTiDe denoising decreased the initial sLFO variance by ⅔, and brainwide FC increased only 27% during the scan.

Conclusions: Non-neuronal sLFO signals are large and intermingled with neuronal BOLD. With careful modelling, however, these signals can be efficiently parsed in BOLD data. If these signals are not separated, neuronal connectivity will be conflated with ANS effects, yielding spurious results. Conversely performing this processing step provides a new, rich ANS information source from existing data.

Disclosure: Nothing to disclose.

20.4 Dynamic brain signals in addiction: clinical relevance of neuronal and non-neuronal fMRI components

Abstract Not Included

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21. The Emerging Role of the Cerebral Cortex in Sleep Regulation

21.1 Novel tools to study sleep-active cortical neurons

Thomas Kilduff

SRI International, Menlo Park, California, United States

Background: We previously identified a cortical GABAergic neuron population that is active during slow wave sleep (SWS) in three rodent species. These cells co-express somatostatin (Sst), neuronal nitric oxide synthase (Nos1), Neurokinin-1 receptor (Tacr1) and chondrolectin (Chodl). These SNTC cells are the Type 1 nNOS neurons that have long-range intracortical projections. SNTC cells express c-Fos during SWS proportional to homeostatic sleep drive. We have proposed that cortical SNTC cells link sleep drive arising from subcortical regions with EEG SWA through their long-range projections. Here, we utilized Tacr1-T2A-Cre;Sst-IRES-FlpO mice and an enhancer virus to investigate the role of cortical SNTC neurons in sleep/wake.

Methods: Expt 1: To label SNTC neurons (1) Tacr1-T2A-Cre; Sst-IRES-FlpO mice were bred with Ai65 mice and (2) the AiP12689 enhancer virus (EV) was injected retro-orbitally into C57BL6/J mice. The sensitivity/specificity of each was determined by nNOS immunohistochemistry. Expt 2: SNTC neuron responses to Substance P were measured by slice electrophysiology. Expt 3: One group of mice underwent 6h sleep deprivation (SD) and another group was allowed 2h of recovery sleep (RS) after 6h SD. Expt 4: AAV8.nEF.Con/Fon.DREADD(Gq)-mCherry.WPRE.hGH was injected at 16 sites across the cortex in Tacr1-Cre;Sst-FlpO mice implanted for EEG/EMG recording. For chemogenetic activation, deschloroclozapine (DCZ; 0.3mg/kg, i.p.) or saline was administered at ZT18 on alternate recording days.

Results: Expt 1: Sensitivity/specificity of Tacr1/Sst/Ai65 cells and EV cells for nNOS protein was 91.5%/59.2% and 65.0%/85.5%, respectively. Expt 2: Substance P activated 78% of Tacr1/Sst/Ai65 neurons (14/18 cells) and 67% of EV cells (8 of 12). Expt 3: Consistent with our previous findings, 64.5+/−1.2% of Tacr1/Sst/Ai65 neurons expressed c-Fos during RS compared to 4.8+/−0.3% during SD (p < 0.0001). Expt 4: As shown by the Batista-Brito lab in Nos1/Sst mice, chemogenetic activation of cortical Tacr1/Sst neurons increased NREM sleep (p = 0.0041).

Conclusions: Consistent with our previous results, Tacr1/Sst/Ai65 cells are active during sleep. Moreover, activation of these cells can drive NREM sleep. These observations show that Tacr1-Cre;Sst-FlpO mice and the AiP12689 EV will be useful to characterize the role of SNTC neurons in sleep/wake control.

Disclosure: Nothing to disclose.

21.2 Bidirectional modulation of sleep in mice via prefrontal cortex chemogenetics

Lukas Krone

University of Oxford, Oxford, United Kingdom

Background: The prefrontal cortex (PFC) enables mammals to perform the most complex cognitive tasks. It is also the first to ‘get tired’: PFC functions are among the earliest to become compromised during sleep deprivation, and electrophysiological markers of sleep pressure increase most prominently in this region. However, the possibility that PFC activity not only reflects sleep need but also actively contributes to sleep homeostasis—the regulation of sleep as a function of prior wake duration and intensity—has been largely overlooked. In this study, we tested the hypothesis that layer 5 pyramidal neurons—the primary output neurons of the PFC—regulate sleep depth and duration under varying levels of sleep pressure.

Methods: We employed a viral vector strategy to express inhibitory and excitatory Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) in layer 5 pyramidal neurons of the mouse PFC. We assessed sleep-preparatory behaviors and sleep initiation, alongside chronic EEG/EMG recordings to quantify sleep amount, architecture, and electrophysiology. In a counterbalanced design, mice received intraperitoneal injections of low-dose clozapine-N-oxide (CNO) or saline under low, medium, and high sleep pressure conditions to compare the effects of DREADD activation with control.

Results: Chemogenetic inhibition increased the amount of NREM sleep during the first two hours following DREADD activation compared to saline control and modulated sleep architecture and electrophysiological parameters in a manner consistent with increased sleep depth. The most pronounced NREM sleep increase was observed under low sleep pressure conditions. In contrast, chemogenetic excitation reduced NREM sleep and altered sleep architecture and electrophysiology in a pattern indicative of reduced sleep efficiency, particularly under high sleep pressure conditions.

Conclusions: Our findings demonstrate that bidirectional modulation of sleep homeostasis markers can be achieved through excitation and inhibition of a subpopulation of layer 5 pyramidal neurons in the mouse PFC. Alongside recent evidence implicating other PFC neuronal populations in sleep regulation, this positions the PFC as a promising target for neuromodulatory strategies to modulate sleep in human sleep studies and clinical settings.

Disclosure: Nothing to disclose.

21.3 Neocortical long-range GABAergic neurons coordinate state-dependent network synchronization and promote sleep

Renata Batista-Brito

Albert Einstein College of Medicine, Bronx, New York, United States

Background: Cortical brain states shift with behavioral states such as sleep and wakefulness, marked by dynamic changes in network synchronization. While subcortical circuits are classically viewed as drivers of these state transitions, the role of neocortical circuits—particularly inhibitory neurons—in regulating local cortical dynamics remains unclear. We investigate a rare, conserved population of long-range inhibitory neurons that co-express somatostatin (Sst), neuronal nitric oxide synthase (Nos1, also known as nNOS), the Neurokinin-1 receptor (Tacr1), and chondrolectin (Chodl), i.e., “SNTC cells.”

Methods: We used 2-photon calcium imaging in head-fixed mice to record SNTC cell activity across defined behavioral states, alongside simultaneous measures of movement and local field potentials (LFPs). To test causality, we manipulated SNTC activity using optogenetics (local stimulation) and chemogenetics (pan-cortical activation). Multisite electrophysiology assessed network-wide effects.

Results: SNTC cells were selectively active during NREM sleep and quiet wakefulness—low-arousal states characterized by high LFP synchrony. Local optogenetic stimulation of SNTC cells induced synchronized cortical states, increasing low-frequency LFP power and spike synchrony, regardless of the animal’s global behavioral state. These effects propagated across cortical areas, consistent with SNTC cells’ widespread projections. Pan-cortical chemogenetic activation of SNTC cells promoted sleep, reducing sleep latency and increasing total sleep time.

Conclusions: Our findings reveal SNTC cells as key cortical effectors of state-dependent synchronization. These neurons not only read out global behavioral state but also influence it, actively promoting sleep. This challenges the classical view of subcortical control of sleep and supports a cortical contribution to the generation and modulation of brain states.

Disclosure: Nothing to disclose.

21.4 The Roles of Calcium and Phosphorylation in Excitatory and Inhibitory Neurons in Sleep Homeostasis

Abstract Not Included

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22. Smartphones, Social Media, and Adolescent Brain, Behavior, and Physical Health: Leveraging Big Data and Novel Methods to Unravel Contributions of Technology to Health in the Digital Era

22.1 Smartphone ownership in youth is associated with poorer cognition and differences in cortical thickness

Arielle Keller

University of Connecticut, Storrs, Connecticut, United States

Background: The transition from childhood to adolescence is a critical developmental inflection point marked by substantial cognitive and neurobiological maturation. Some, but not all, youth acquire smartphones during this time period, yet the effect of smartphone ownership on cognitive neurodevelopment remains unclear.

Methods: Here, we leverage a naturalistic experiment in a large longitudinal sample of youth from the Adolescent Brain Cognitive Development (ABCD) Study (n = 7807, ages 11–15, 46.82% female), where a subset of these participants (72%) reported acquiring a smartphone (n = 5621, 48.94%). We assess cognition using performance on behavioral tasks from the NIH Toolbox and assess brain structure using cortical thickness across brain regions defined by the Desikan-Killiany brain atlas. We model associations of smartphone ownership and age of smartphone acquisition with cognition and brain structure using mixed-effects regression with random intercepts.

Results: First, we find that smartphone ownership and earlier age of smartphone ownership onset are consistently associated with poorer cognitive performance on memory, vocabulary, and reading tasks (Picture Sequence Memory: psFDR < 0.001; Picture Vocabulary: psFDR < 0.001; Reading Recognition: psFDR < 0.001) but not on tasks assessing general executive functioning (Flanker Task, Pattern Comparison Processing Speed). Second, we find that smartphone ownership and is associated with lower cortical thickness in occipital regions such as the bilateral cuneus, pericalcarine, and lateral occipital cortices and left lingual gyrus (psFDR < 0.05) as well as higher cortical thickness in frontal regions such as the bilateral pars opercularis and left hemisphere pars orbitalis and superior frontal cortices (psFDR < 0.05). Aligning with this pattern, younger age of onset for smartphone ownership is associated with lower cortical thickness in occipital cortices (psFDR < 0.05) and higher cortical thickness in frontal cortices (psFDR < 0.05).

Conclusions: These results suggest that youth smartphone ownership may be associated with poorer cognition and different patterns of structural neurodevelopment in the occipital and frontal cortices.

Disclosure: Nothing to disclose.

22.2 Beyond screentime: how smartphone ownership and the digital exposome shape adolescent mental and physical health

Ran Barzilay

Perelman School of Medicine University of Pennsylvania, Philadelphia, Pennsylvania, United States

Background: Adolescent health is increasingly shaped by the digital environment, particularly through widespread smartphone use, yet the specific health impacts of smartphone use and related digital exposures remain unclear.

Methods: Utilizing data from the Adolescent Brain Cognitive Development (ABCD) Study, we tested longitudinal associations between smartphone ownership and depression, obesity, and sleep outcomes in thousands of U.S. youth from ages 12 to 14. Multivariable models adjusted for multiple confounders (e.g., demographics, puberty, parental monitoring). We applied data-driven methods to characterize the digital exposome, enabling us to disentangle distinct health effects of smartphone engagement duration (screentime) from those of specific online experiences (e.g., social media use, cyberbullying).

Results: Smartphone ownership increased from 63.7% to 89.1% across three annual assessments (mean ages 12.0, 12.9, and 14.1). Smartphone owners had higher odds of depression (OR = 1.38, 95% CI: 1.09–1.75, p = 0.001), obesity (OR = 1.31, 95% CI: 1.01–1.69, p = 0.013), and insufficient sleep (OR = 1.63, 95% CI: 1.47–1.80, p < 0.001), with these effects more pronounced in girls. Among youth without a smartphone at age 12 (n = 3486), acquiring a smartphone by the subsequent annual follow-up (n = 1546) was associated with increased psychopathology and reduced sleep compared to those who remained without a smartphone (n = 1940), even after adjusting for prior mental health and sleep. Accounting for several offline confounders, screentime was longitudinally associated with depression (OR =1.26, 95% CI: 1.09–1.47, p = 0.001), obesity (OR = 1.43, 95% CI: 1.25–1.63, p < 0.001), and insufficient sleep (OR = 1.53, 95% CI: 1.35–1.72, p < 0.001). However, further adjustment for online (digital exposome) factors eliminated the association between screentime and depression (OR = 1.03), while only modestly attenuating associations with obesity (OR = 1.38) and insufficient sleep (OR = 1.33).

Conclusions: Smartphone ownership and specific digital exposures are independently associated with various adverse early-adolescence health outcomes. Prevention efforts for adolescent depression should prioritize the quality and context of digital engagement rather than focusing solely on reducing screentime.

Disclosure: Taliaz Health, Advisory Board, Self, Taliaz health, Stock / Equity - Privately Held Company, Self

22.3 Daily links from adolescent smartphone communication to mood and depression

David Pagliaccio

New York State Psychiatric Institute, Columbia University, New York, New York, United States

Background: Smartphones and social media have become central to adolescent’s social lives. Concerns have been raised about the impact of smartphones and digital communication on mental health. Yet, research has been fairly inconclusive, yielding small or mixed effects and little support for causal associations. Intensive longitudinal studies allow for nuanced temporal examination of potential bidirectional effects between smartphone communication and youth depression.

Methods: Adolescents (13–18 years) were recruited as part of two studies on mental health. Data was analyzed from N = 135 youth from a study on depression recurrence and N = 145 youth from a study on suicide risk. All youth completed clinical interviews on their mental health. Youth installed the Effortless Assessment Research System (EARS) app on their personal smartphone to collect daily mood and passive smartphone sensor data for 6 or 12 months. Quantity, timing, and content of smartphone keyboard usage was linked to daily mood.

Results: Greater quantity of social communication (number of characters, person-mean-centered) related to worse next-day mood. Using more personal pronouns in social apps related to lower daily affect. Effects were driven by texting apps, particularly in the morning. Effects were generally small in magnitude (np2 < .003). Higher daily sentiment (more positive than typical) related to higher daily affect. This was consistent across both samples (B > 1.49, Z > 7.33, p < .001). Sentiment effects were seen across texting and social media. Preliminary analyses suggest specific language content around depressive mood further predicts worse daily mood, beyond negative sentiment.

Conclusions: Replicating across two cohorts of adolescents, greater quantity of outgoing smartphone communication and more negative sentiment related to worse mood day-to-day. Effects were specific to social vs. non-social usage. Quantity of direct messaging was more impactful than social media, whereas sentiment was predictive in both types. More self-focus (first-person pronouns), was also linked to worse mood. Communication during morning and late-night may be most predictive. Results support our understanding of the temporal impact of smartphone communication and potential directions for just-in-time interventions triggered by smartphone sensors.

Disclosure: Nothing to disclose.

22.4 Understanding social media’s role in mental health: causal perspectives and interdisciplinary pathways

Abstract Not Included

Mini Panel

23. Potential Benefits of Buprenorphine for Suicidality

23.1 Suicidal ideation trajectories in a comparative effectiveness trial of buprenorphine-naloxone vs. extended-release naltrexone for opioid use disorder

Mina Rizk

Icahn School of Medicine At Mount Sinai, New York, New York, United States

Background: Individuals with opioid use disorder (OUD) are at elevated risk for suicide. While OUD treatments improve co-morbid depression, their effects on suicidal ideation remain unclear. This study examined changes in suicidal ideation during treatment with buprenorphine-naloxone or extended-release naltrexone in treatment-seeking adults with OUD.

Methods: 570 adults with OUD (29.6% female) were recruited into a National Drug Abuse Clinical Trials Network randomized trial (NCT02032433) comparing extended-release naltrexone (n = 283) versus buprenorphine-naloxone (n = 287) for opioid relapse prevention (X:BOT). Suicidal ideation was assessed at baseline and regular intervals over 24 weeks using continuous self-reported and binary clinician-rated measures from the Concise Health Risk Tracking-Self Report and the Hamilton Depression Rating Scale, respectively. A linear mixed-effects model was conducted with continuous self-reported suicidal ideation as the outcome, and time, treatment, and baseline suicidal ideation as covariates. Similarly, a logistic model was fit for the binary clinician-rated suicidal ideation measure.

Results: Continuous self-report suicidal ideation scores decreased in both groups with a significant time-by-treatment interaction indicating that the treatment effect differed over time (F(11, 3497) = 1.81, p = 0.0464). Scores were lower in the buprenorphine group only in weeks 1 (p = 0.0022) and 3 (p = 0.0496) and when averaged across weeks 1–4 (p = 0.0343). In both groups, the continuous self-reported suicidal ideation scores dropped rapidly over the first 4 weeks of treatment (F(11,3508) = 5.94, p < 0.0001). Binary clinician-rated suicidal ideation dropped from 15 (5.25%) and 12 (4.24%) at baseline, to 5 (1.89%) and 3 (1.49%) at week 1, with buprenorphine and naltrexone, respectively. Odds of binary clinician-rated suicidal ideation were significantly different between the treatment groups across all visits, with odds for the buprenorphine group 53% lower than those for the naltrexone group (OR = 0.47, p = 0.0348).

Conclusions: OUD treatment with extended-release naltrexone or buprenorphine-naloxone was associated with suicidal ideation reductions from the first week. Suicidal ideation was slightly lower with buprenorphine-naloxone in the first 4 weeks, with no differences thereafter. Despite low baseline severity and modest between-group differences, findings suggest that both medications may have beneficial effects on suicidal ideation in individuals with OUD.

Disclosure: Nothing to disclose.

23.2 A randomized controlled trial of low-dose buprenorphine to prolong ketamine’s antisuicidal effects in treatment-resistant depression

Igor D. Bandeira

Stanford University School of Medicine, Stanford, California, United States

Background: Suicide continues to pose a major global public health concern, with increasing rates in the United States and limited effective treatments for acute suicidal crises. Ketamine, an NMDA receptor antagonist, has shown rapid and substantial reductions in suicidal ideation, offering an important option for individuals in acute suicidal states. However, the transient nature of ketamine’s antisuicidal effects and concerns surrounding repeated use highlight the need for strategies to sustain its benefits. Preclinical and clinical findings suggest that opioid receptor activity may play a role in mediating ketamine’s therapeutic effects. Notably, recent data indicate that low-dose buprenorphine can produce significant clinical benefits starting two weeks into treatment. Building on these findings, we evaluated the efficacy and safety of low-dose buprenorphine—a partial mu-opioid receptor agonist—as a maintenance strategy following ketamine administration.

Methods: We conducted a randomized, double-blind, placebo-controlled trial involving patients with suicidal ideation who met criteria for Major Depressive Disorder or Bipolar II Disorder during a current major depressive episode (MDE), all of whom exhibited treatment resistance. Participants first received a single open-label intravenous ketamine infusion (0.5 mg/kg over 40 minutes). Forty-eight hours later, they were randomized 1:1 to receive either low-dose buprenorphine (0.2 mg/day, titrated to a maximum of 0.8 mg/day) or placebo for four weeks, followed by a two-week safety follow-up. The primary outcome was the change in suicidal ideation measured by the Beck Scale for Suicide Ideation (BSSI) from day 1 to day 31. The secondary outcome was change in depressive symptoms, assessed by the Montgomery-Åsberg Depression Rating Scale (MADRS). We used linear mixed-effects models to evaluate treatment effects over time.

Results: Fifty participants received IV ketamine and were randomized; five withdrew before completing one week of follow-on treatment. Both groups showed significant reductions in BSSI scores (ketamine + buprenorphine: Δ mean = −11.3 ± 6.4, n = 23; ketamine + placebo: Δ mean = −7.7 ± 6.7, n = 22). However, the buprenorphine group exhibited significantly greater reductions in suicidal ideation over the study period (time-by-treatment interaction: p < 0.001; Glass’s d = 0.7). No significant differences were found between groups in depression severity.

Conclusions: Low-dose buprenorphine significantly extended the antisuicidal effects of a single ketamine infusion for at least four weeks in patients with treatment-resistant depression. This represents the first pharmacological approach shown to sustain ketamine’s antisuicidal efficacy over time.

Disclosure: Nothing to disclose.

23.3 Geographic and temporal patterns of buprenorphine dispensing and associations with opioid-related suicides and unintentional overdose deaths

Yunyu Xiao

Weill Cornell Medical College of Cornell University, New York, New York, United States

Background: Opioid-related suicides and unintentional overdose deaths have increased dramatically across the U.S. over the past three decades. Buprenorphine may reduce suicidal ideation and risks of opioid-related deaths. Prior studies found that counties in the U.S. with high buprenorphine dispensing had lower opioid-related suicide and overdose death rates. However, whether such associations differed geographically and temporally remains unaddressed.

Methods: This cross-sectional study included buprenorphine dispensing from the IQVIA Claims Database and opioid-related suicides and unintentional overdose deaths, as well as total suicides from the Centers for Disease Control and Prevention WONDER database across 3147 U.S. counties between 2007 and 2018. County-level geographical and temporal distributions of buprenorphine dispensing and suicide and death rates were calculated and aggregated into three-year intervals. Spatial associations of the buprenorphine dispensing with opioid-related suicides and unintentional overdose deaths were estimated by geographically weighted regression (GWR) models controlling for age, sex, and race/ethnicity. Negative binomial models were tested in sensitivity analyses.

Results: From 2007 to 2018, buprenorphine dispensing rates in the U.S. increased steadily from 0.7 to 3.2 per 100. Counties with high buprenorphine dispensing rates were both clustered in New England and central Appalachia and sparsely located in the Midwest and West, with the highest dispensing rates increasing from 33.6 in 2007–2009 to 189.8 in 2016–2018. Spatial association analysis by GWR models showed that more buprenorphine dispensing were associated with higher opioid-related suicide rates in the West and Southwest and such associations decreased from the years of 2007–2009 to 2016–2018 (highest GWR coefficient from 0.19 to 0.13, p-value < 0.05). More buprenorphine dispensing in the West, Northwest, and Southwest were correlated with higher unintentional overdose death rates across the years, with such positive associations decreasing from the years of 2007–2009 to 2016–2018 (highest GWR coefficient from 4.41 to 2.23, p-value < 0.05). Counties in the Southwest and Northwest reported positive associations between buprenorphine and total suicide rates (highest GWR coefficients: 0.9–1.9, p-value < 0.05). Negative binomial regression showed weak (coefficients: 0.003–0.034, p-value < 0.05) or insignificant associations of buprenorphine dispensing with opioid-related suicides, unintentional overdose deaths and total suicides.

Conclusions: Buprenorphine dispensing increased from 2007 to 2018 and concentrated in New England and central Appalachia. Contrary to prior research, results revealed that counties with high level of buprenorphine prescriptions also experienced more opioid-related suicides, unintentional overdose deaths, and total suicides in the western U.S. over the years. It is possible that the buprenorphine prescription rate reflects levels of opioid use disorder (OUD) and are also insufficient or ineffective in controlling suicide risk in this population. Burpenorphine has been shown to reduce suicidal ideation in depressed patients but has not been tested in a randomized controlled trial for this effect in OUD. The findings highlight the need for studies of buprenorphine antisuicidal effects in both OUD and major depression.

Disclosure: Nothing to disclose.

Study Group

24. How to Compare Developmental Stages Across Species?

Christoph Kellendonk, Sarah Canetta, Ileana Hanganu-Opatz, Mark Ansorge, Kristen Delevich, James Bourne, Marta Andujar, Laurel Gabard-Durnam

Columbia University/New York State Psychiatric Institute, New York, New York, United States

Study Group Summary: Understanding the developmental risk factors and brain alterations preceding onset of psychiatric and neurological disorders can open new avenues for earlier and more effective intervention and even prevention. However, human studies of development are limited both ethically by the potential vulnerability of this population and technically by the inability to determine who will develop a particular disease later in life. Animal studies of development can therefore provide valuable complimentary insights. Key to maximizing the utility of these studies, however, is our ability to translate developmental stages across species. Despite the importance of this question, it remains contentious how to define these cross species developmental equivalencies. In this panel, we will explore this topic by examining evidence from multiple metrics of development in rodents, monkeys and humans. Our panelists will tackle several key and timely questions on this topic as outlined below.

Disclosure: Nothing to disclose.

Mini Panel

25. Precision Medicine in Bipolar Disorder - Targeting Molecular Mechanisms of Pathophysiology

25.1 Probing the role of sodium and potassium channels in modulating neuronal excitability in human iPSC-derived cortical neurons

Rakesh Karmacharya

Harvard University, Boston, Massachusetts, United States

Background: Aberrant neuronal excitability is hypothesized to play a role in the disease biology of bipolar disorder (BP). Several current and putative therapeutics for BP regulate the activity of specific ion channels. Examples include lamotrigine, which modulates the activity of voltage-gated sodium channels, and beta-hydroxybutyrate, which modulates the activity of potassium channels. The molecular mechanisms mediating their effects on mood stabilization are not known. Human cortical neurons differentiated from induced pluripotent stem cells (iPSCs) of BP patients provide new avenues to interrogate mechanisms mediating clinically relevant effects of these treatments. Systematic electrophysiological analyses can be utilized to decode BP-specific channelopathies that modulate neuronal activity and dissect mechanisms of putative therapeutic agents.

Methods: Cortical neurons from 6 control and 6 BP iPSC lines (3M, 3F) were studied in the setting of exposure to lamotrigine, using dose-response (0.1 uM-100 uM) and time-course (30 min-24 hr) experiments. Electrical activity was recorded using microelectrode arrays (MEA). Neuronal excitation was induced with high potassium (25–50 mM), low magnesium (0.1–0.5 mM), and MEA stimulation (biphasic square pulses; 100–1,000 mV). We collected MEA data in cortical neurons exposed to acute or chronic lamotrigine treatment in presence of annotated ion channel blockers (0.1–10 uM from the following categories: phase 1 action potential (i.e., voltage-gated sodium channel blockers) and phase 2 action potential (i.e., voltage-gated potassium and HCN channel blockers). MEA recordings were validated using the voltage-sensitive dye PMPI (plasma membrane potential indicator). Lastly, we explored potential synergy between lamotrigine and ketosis-like conditions. To emulate ketosis-like conditions, we constituted a chemically defined medium supplemented with concentrations of glucose and beta-hydroxybutyrate (BHB) that maximized the activity of the beta-hydroxybutyrate dehydrogenase 1 (BDH-1), the rate-limiting enzyme in ketone metabolism that converts BHB to acetoacetate. We recorded electrophysiological and metabolic activity using an MEA and Seahorse Mito Stress test, respectively.

Results: Preliminary studies to date show that lamotrigine exerts disease-specific effects on neuronal activity in BP cortical neurons vis-à-vis healthy control neurons, in a dose-dependent manner. The MEA studies further show that excitatory stimulation modulates the electrophysiological effects of lamotrigine in the cortical neurons, and this is influenced by culturing the neurons under ketosis-like conditions. We show that phase 1/phase 2 ion channel blockade disrupts stimulation and interferes with the effects of lamotrigine.

Conclusions: This study begins to inform our understanding of the mechanistic underpinnings of mood-regulatory potential of anticonvulsants like lamotrigine. Furthermore, we found potential cross-talk between lamotrigine and cellular effects of ketosis, providing new hypotheses for synergy between two disparate therapeutic strategies.

Disclosure: Nothing to disclose.

25.2 Attenuated CaV1.2-BK channel interaction as a molecular signature of ‘switch’ in bipolar disorder

Rupali Srivastava

Johns Hopkins University School of Medicine, Baltimore, Maryland, United States

Background: Bipolar disorder (BP), the manic-depressive major mental disorder is a challenging disorder to treat due to its multifactorial nature including genetic, environmental and epigenetic factors. Medications based on molecular understanding and targeting a larger patient population are warrant, We sought to understand molecular deficits with a focus on calcium and potassium ion channel functioning in light of clinical phenotype of the patients (broader category, including both lithium responders and non-responders) for identifying novel drug targets. We also characterized a novel mouse model to study the ‘behavior switch’.

Methods: Excitatory induced neuronal (iN) cells from 25 healthy control and 25 BP patients were utilized for the initial calcium kinetics studies and the correlation analysis with the clinical phenotypes. Linear regression analysis adjusting for age, gender, race, smoking status, duration of illness, cuprizone, and mood stabilizer usage were conducted to test the correlations between calcium kinetics readouts and the main clinical variables, including number of manic episodes, number of depressive episodes, number of total episodes, global assessment scale, young mania scale total, ALDA total score. Induced pluripotent stem cells (iPSC)-derived excitatory neurons from 5 healthy controls and 5 stratified BP patients were generated for further calcium kinetics, electrophysiological and protein interaction studies using proximity ligation assay. The mouse model studies were done with a minimum of 10 black 6J male mice in each condition for each experiment. Behavior assays of forced swim test and sucrose splash test were used for characterizing ‘behavior switch’. Data analysis was performed the Graph pad prism, with ANCOVA for multiple comparisons, and t-test for in-group comparison.

Results: We discovered blunted calcium kinetics especially the delayed time to peak (p < 0.01), and found them to be stemming from the aberrant interaction between voltage gated calcium channel CaV1.2 and calcium-potential activated big potassium (BK) channel (p < 0.01). We found the number of manic episodes significantly correlated with calcium kinetics readout of blunted time to peak (q = 0.044). We also generated a novel ‘behavior switch’ mouse model by combining BK channel haploinsufficiency with the sleep deprivation stress (p < 0.05). Interestingly, we saw a rescue of the cellular phenotypes of blunted calcium kinetics and electrophysiological properties with BK channel agonists unoprostone and BMS204352 in the BP patient cells derived from both lithium responders and non-responders under clinical settings (p < 0.05). We also observed rescue in ‘behavior switch’ in mouse model by utilizing these agonists (p < 0.05).

Conclusions: The study discovered aberrant CaV1.2-BK channel interaction in the excitatory neuronal cells derived from a broader sub-groups of BP patient samples; and this phenotype resulted in the downstream blunted calcium kinetics: both correlated with the number of mania in BP. Based on these results, the study further defined a novel gene + environment perturbation mouse model exhibiting ‘behavior switch’ thus highlighting the relevance of these channels functioning towards ‘switch’.

Disclosure: Sumitomo Pharma Co. Ltd., Consultant, Self

25.3 Modulation of circadian rhythms for the personalized treatment of bipolar disorder

Colleen McClung

University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Background: Circadian rhythm and sleep abnormalities are a core feature of bipolar disorder (BD). Multiple studies have found that individuals with BD have lower interdaily rhythm stability, greater rhythm fragmentation and weaker amplitudes. There are also dramatic differences in sleep/wake activity patterns as well as the phase of molecular rhythms during manic and depressive episodes. Episodes are also often precipitated by shift work, overseas travel or seasonal changes, indicating an inability to adapt to a new light/dark cycle. Individual rhythmic phenotypes can also predict treatment outcomes, suggesting that a personalized, and even state specific, approach to rhythm alignment and stabilization is needed to achieve optimal therapeutic effects.

Methods: We set out to develop novel pharmacotherapies which will either enhance rhythm amplitude, shift rhythms in a particular way, or facilitate faster and more robust rhythmic entrainment to light. We used computational modeling to perform in silico drug screens at selected targets to identify potential compounds that might achieve the desired effect. Then these compounds were subjected to a variety of assays in cell culture to determine if they bound their target, either activated or repressed specific protein functions, and how they impact molecular rhythmicity using reporter gene assays in both mouse and human fibroblasts. We then tested these compounds in mouse models to determine how they impact sleep/wake activity patterns, the response to light pulses and activity of the core molecular clock in the suprachiasmatic nucleus (SCN).

Results: Here I will discuss two of our approaches. One is work with the compound cordycepin and its novel analogues that we identified in our screens. Cordycepin is a naturally occurring compound that interacts with RuvB-like ATPase 2 and other circadian proteins to regulate circadian phase. We found that cordycepin is able to significantly increase molecular rhythm amplitude (P < 0.01) in cell culture assays and can both phase advance or phase delay rhythms when given at particular times of day. Moreover, in mouse models, i.p. administration of cordycepin and it’s analogues can entrain sleep/wake rhythms and provide a more robust response to light. The second approach involves the identification of novel compounds that bind and activate the circadian photoreceptor, melanopsin in the eye. Melanopsin is the primary photoreceptor by which light entrains the central clock in the SCN. Using computational approaches and then Presto/Tango assays in culture we identified existing as well as novel, custom synthesized compounds which specifically activate melanopsin with no impact on rhodopsin. We also found that oil emulsions can penetrate the retina and lead to significant expression when given via an eye drop. Most importantly we find that when mice are administered these compounds via an eye drop there is a significant activation of cFos in the SCN (p < 0.01), indicating SCN activation and mice show faster and more robust entrainment to a shift in the light/dark cycle (p < 0.05).

Conclusions: These results provide evidence that we can identify and create novel compounds which impact the circadian clock and the entrainment to light in highly specific ways. The development of these therapies can help those with BD either prevent episodes on a daily basis or in situations when they are vulnerable such as travel or before a change in season.

Disclosure: Nothing to disclose.

Panel

26. Neurobiology of Opioid Use Disorder Recovery: Effects of Methadone Versus Buprenorphine

26.1 Different patterns of Mu-opioid receptor availability in opioid use disorder patients treated with methadone or buprenorphine

Jacob Dubroff

Perelman School of Medicine University of Pennsylvania, Philadelphia, Pennsylvania, United States

Background: Methadone (MET), a full mu-opioid receptor (MOR) agonist, and buprenorphine (BUP), a partial MOR agonist, are effective and widely prescribed medications for treating opioid use disorder (OUD). Studies have shown that OUD patients are more likely to be adherent with MET than BUP. Studies with C-11-labeled carfentanil ([11C]CFN), a potent mu opioid agonist radiotracer, show a dose-dependent relationship between BUP and MOR occupancy, which is directly related to the suppression of opioid withdrawal signs and symptoms. We compared MOR availability in OUD patients maintained on MET or BUP with healthy control (HC) subjects using a prototype high-sensitivity, long axial field-of-view PET instrument.

Methods: We recruited 10 OUD patients—5 maintained on MET (5M/0F, mean age 38+/−2 yrs), and 5 on BUP (4M/1F, mean age 36.9+/−5.5 yrs)—and 13 HCs (7M/6F, mean age 29.1+/−8.3 yrs). Subjects underwent 70 min of dynamic PET imaging beginning with the intravenous administration of [11C]carfentanil (range 73.6–313.6 MBq of activity). We used PMOD software for analysis that included motion correction, co-registration with corresponding T1 brain MRI, normalization to the MNI template, and segmentation of the five a priori analysis regions (ventral tegmentum, thalamus, caudate, putamen, amygdala) using the AAL atlas. Distribution volume ratio (DVR) for each region was computed with the Logan reference tissue model using the visual cortex.

Results: MOR availability differed at all five regions (F10,34 = 5.6, p < 0.001). Compared to HCs, MOR availability was significantly lower in the BUP group across all regions (mean 39.1%+/−15.2) (all p < 0.001), and in the MET group in the ventral tegmentum and amygdala (p < 0.05). MOR availability was lower in BUP than MET in the thalamus, caudate, putamen, and amygdala (all p < 0.05). There was an inverse linear relationship between MET serum level and mean MOR availability (R2 = 0.83, p = 0.03) and an inverse logarithmic relationship between BUP level and MOR availability (R2 = 0.96).

Conclusions: MET and BUP are both MOR agonists that limit MOR availability. However, MOR availability was lower in BUP than MET across brain regions. MOR availability and serum levels were inversely related to both MET (linearly) and BUP (logarithmically).

Disclosure: Radmetrix, Contracted Research, Self

26.2 Dopamine receptor imbalance in opioid use disorder recovery

Peter Manza

University of Maryland School of Medicine, Baltimore, Maryland, United States

Background: Opioid use disorder (OUD) is associated with significant changes to the brain dopamine system, including blunted striatal dopamine D2/3 receptor availability and stimulant-induced dopamine release, relative to controls. It remains unknown whether these deficits resolve when individuals cease using opioids and recover from OUD, and whether treatment with medications (e.g., methadone and buprenorphine) affects the trajectory of recovery. Further, little is known about dopamine D1-like receptors, which are crucial for drug reward, nor the D1R-to-D2R ratio, in OUD.

Methods: We enrolled n = 85 people with OUD (52 male, 35 female), including n = 33 prescribed methadone, n = 29 prescribed buprenorphine, and n = 23 in recovery without medications; and n = 40 age/sex/BMI-matched healthy controls (25 male, 15 female), who received 3 PET scans, measuring whole-brain D1R ([11C]NNC112), and striatal D2R ([11C]raclopride) after both a placebo and a methylphenidate challenge (60 mg oral), to assess dopamine release (scans collected on different days).

Results: OUD vs. controls showed markedly higher D1R binding throughout frontal cortex (F = 8.57, p = 4.4e-06) and all striatal nuclei (e.g., for caudate head: F = 5.24, p = 6.5e-04). There were no significant deficits in striatal D2R nor in methylphenidate-induced dopamine increases (all p > 0.05). Together, this resulted in a greatly elevated D1R-to-D2R ratio for people with OUD, in all striatal nuclei (e.g., for caudate head: F = 6.63, p = 8.9e-05). No measures were significantly associated with OUD treatment duration (e.g., D1R in caudate head: r = 0.13, p > 0.05). There were no significant differences between: 1) males and females; 2) methadone/buprenorphine subgroups; 3) OUD medication subgroups and the ‘no medications’ OUD group.

Conclusions: People in OUD recovery, with or without medications for OUD, do not show deficits in D2R binding nor stimulant-induced dopamine increases, in contrast to prior studies in active OUD. The elevated D1R in OUD might reflect persistent changes and/or predisposing risk factors. Our findings document potential evidence of recovery on D2R signaling and dopamine release, indicative of their beneficial effects to brain recovery and distinguishing them from continued misuse of opioids.

Disclosure: Nothing to disclose.

26.3 Relationships Between opioid abstinence network strength, craving, and relapse in OUD patients maintained on methadone vs. buprenorphine

Margaret Davis

Yale University School of Medicine, Waterbury, Connecticut, United States

Background: Understanding the pathophysiology of opioid use and opioid use disorder (OUD) is essential to developing targeted strategies for prediction, prevention, and treatment. Promisingly, recent work by Lichenstein et al. (2021) used connectome-based predictive modeling (CPM) to identify patterns of connectivity associated with opioid abstinence vs. relapse (opioid abstinence network; OAN). Importantly, all participants in the original study were maintained on methadone (MET) precluding examination of potential differential effects of other maintenance therapies. The present study examined differences in OAN network strength among individuals with OUD maintained on MET vs buprenorphine (BUP) relative to healthy controls (HC).

Methods: Eighty-three individuals with OUD (31% female n = 49 BUP, n = 30 MET; 45% currently abstinent) and N = 90 HC (41% female) were recruited and completed 8-minute resting state magnetic resonance imaging (480TRs, TR = 1s). A subsample of n = 23 OUD and n = 18 HC participants completed 2+ scans each (total = 120 OUD scans, 109 HC scans). Network strength was computed using CPM-derived OAN weights (Lichtenstein et al., 2021).

Results: Consistent with original work, no group differences (MET, BUP, HC) were observed in aggregate OAN strength (F(2,229) = 0.399, P = 0.671; BUP vs. MET (B = −0.006, t = −0.53, P = 0.59)). Across OUD participants, OAN strength was related to past week (B = −0.005, P = 0.006), and current (B = −0.007, P = 0.006) opioid craving (less OAN involvement, higher craving). Interestingly, the relationship between OAN and current craving was stronger (Med*craving = B = −0.013, P = 0.015) in MET (B = −0.017, p < 0.001) vs. BUP (B = −0.004, P = 0.252). Subgroup analyses comparing network strength within and across MET/BUP participants based on follow-up (persistent abstinence vs. relapse at 90-days) will also be presented.

Conclusions: OAN strength did not differ across MET, BUP, and HC. However, OAN strength was inversely related to intensity of current and recent opioid craving across participants, and a stronger relationship between OAN and current craving was observed in MET. Preliminary analyses provide further support for significance of the OAN in OUD, with findings largely consistent across MET and BUP. Consideration of differences in the association between OAN and relapse across MET vs. BUP is a crucial next step.

Disclosure: Nothing to disclose.

26.4 Preliminary evidence for lower kappa opioid receptor availability in people with opioid use disorder: a positron emission tomography study with the agonist radiotracer [11C]EKAP

Gustavo Angarita

Yale University School of Medicine, New Haven, Connecticut, United States

Background: The kappa opioid receptor (KOR) /dynorphin system is an “anti-reward system” during withdrawal from opioids.

Findings from animal models support KOR medications as potential treatments for opioid use disorder (OUD).

Mixed findings have been reported regarding the relationship between the KOR system and opioid use in preclinical and clinical studies.

We aimed to determine whether differences in KOR were present in OUD with positron emission tomography (PET) imaging using the KOR-specific radiotracer [11C]EKAP.

Methods: Eleven individuals with DSM-5 OUD and 7 demographically matched healthy control (HC) subjects participated in a single PET scan.

OUD participants completed scanning after ≥7 days of inpatient detox (with buprenorphine or without opioid agonist agents) or as outpatients (with methadone); HC data obtained from our historical dataset.

Arterial line was placed, and blood samples were collected and analyzed during the scan to measure the tracer concentration over time as the input function for quantification of total volume of distribution (VT).

VT was defined by the ratio of tracer concentration in regions of interest (ROI)(i.e., amygdala, caudate, hippocampus, insula, putamen, and thalamus) to plasma at equilibrium. [11C]EKAP VT was estimated with multilinear analysis-1 (MA1, t* = 20 min) as previously validated.

Results: Lower [11C]EKAP VT was found in individuals with OUD (10.1 ± 3.2mL/cm3) compared with HC (13.9 ± 1.9mL/cm3) in the composite brain region, with a large effect size (−27%, d = 1.4, p = 0.01).

There was no difference in VT between OUD subgroups: H(4), p = 0.13. Comparing VT between OUD subgroup without opioid agonist agents (n = 2; 11.2 ± 0.3) and those treated with methadone (n = 3; 13.0 ± 4.5) revealed no significant differences: U = 2, p = 0.8.

Comparison between group without opioid agonist agents and those treated with buprenorphine (n = 6; 8.2 ± 1.5) revealed non-significant trend value: U = 0, p = 0.07.

Conclusions: Preliminary findings provide in vivo evidence of lower KOR-binding in key limbic structures for OUD.

We found no significant difference in availability between OUD subgroup without an opioid agonist agent and with MOUD.

Future studies are warranted to replicate results and to investigate the relationship between lower binding of KOR and clinical outcomes.

Disclosure: Nothing to disclose.

Panel

27. Neuroimaging-Guided Precision Brain Targeting in Mood Disorders

27.1 Biomarker informed optimization of DBS for depression

Helen Mayberg

Icahn School of Medicine at Mount Sinai, New York, New York, United States

Background: Longitudinal antidepressant effects of Subcallosal Cingulate Deep Brain Stimulation (SCC DBS) can now be indexed using multiple methods. Chronic electrophysiological monitoring of local field potentials (LFP) using next generation DBS systems, combined with multimodal serial MRI scanning enables further characterization of this chronology.

Methods: A LFP biomarker of stable DBS response, developed using explainable-AI (PC + S, n = 6, weekly in lab x 7mo; Alagapan Nature 2023) was evaluated in a new TRD cohort (RC + S, n = 7, BID home recordings, stim on/off x 7mo). Biomarker performance was evaluated under varying conditions (am/pm; on/off DBS). A third cohort (Percept, n = 7) additionally underwent 3.0T MRI (high-res T1, diffusion, and resting-state) at fixed time points during chronic DBS (baseline, 1, 3, 6 mo). Fractional Anisotropy (FA) in stimulated white matter (WM) bundles (forceps minor, FM, cingulum bundle, CB, and uncinate fasciculus, UF), and normalized Amplitude of Low-Frequency Fluctuations (ALFF) from 17-resting state networks were extracted and longitudinal changes were evaluated. Baseline abnormalities predicting timeline to stable LFP response was also assessed.

Results: The performance of the LFP biomarker to predict recovery status as indexed by weekly HDRS-17 was robust (accuracy: mean ROC AUC = 0.72 ± 0.2; original cohort: 0.85 ± 0.1), confirming reliability and consistency under different recording conditions. Similarly, WM integrity and SCC functional connectivity at baseline replicated the timeline of LFP response (rho = 0.9; p < 0.001). Increases in FA in L-CB, and bil UF (corrected p < 0.05); and increased ALFF in default mode network (corrected p < 0.05) were seen over time in Cohort 3 and correlated with changes in HDRS-17, similar to the FDG PET changes seen previously (Cha, Mol Psych 2024).

Conclusions: These findings support the feasibility and reliability of standardized brain-based biomarkers for objectively defining and tracking depression recovery with SCC DBS across platforms. These and related biomarkers will be critical to future scaling of DBS for depression and may further define mechanisms mediating the durable effects of this intervention.

Disclosure: Abbott Neuromodulation, Consultant, Self, Abbott Neuromodulation, Patent, Self, Cogwear, Advisory Board, Self, BlackRock Neuro, Advisory Board, Self, NextSense, Advisory Board, Self.

27.2 Identification, replication and targeting feasibility of a novel neuromodulation target for mania/hypomania: toward precision brain targeting in bipolar disorder (BD)

Mary Phillips

University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Background: We reported a positive relationship between reward/salience network left ventrolateral prefrontal cortex (vlPFC) activity to reward expectancy (RE) and mania risk in independent adult samples. We aimed to identify associations among left vlPFC functional connectivity (FC) and mania vs. depression risk; and feasibility of using Theta Burst Stimulation (TBS) to reduce mania symptoms by reducing RE-related left vlFPC activity.

Methods: In a discovery at risk sample (n = 171, 66%-female, 23.70 ± 3.35 yrs), we examined associations between RE-related left-vlPFC-wholebrain FC and MOODS self-report [MOODS SR] manic and depressive domain total, and cognitive, mood, energy subdomain, scores; and if these findings replicated in an independent at risk test sample (n = 232, 71.1% female; 21.68 ± 2.00 yrs). In an ongoing double-blinded study in BD and controls (present n = 57, 72% female; 25.58 + /−5.21 yrs), we target left vlFPC and control region left somatosensory cortex with continuous (inhibitory) TBS; and left vlPFC, with sham TBS. We examine relationships between pre-to-post TBS changes in RE-related left vlPFC activity and mania-linked arousal (Internal State Scale[ISS]-Activation) in each TBS condition (blinded: A,B,C).

Results: Discovery sample: There were positive associations between left-vlPFC–right central executive network dorsolateral prefrontal cortex (dlPFC) FC and MOODS depressive total and cognition scores (Pfwe < 0.05, cluster-level). Using extracted FC parameter estimates from this analysis, left vlPFC–right dlPFC FC was negatively associated with MOODS manic cognition score (β = –0.093, p < 0.001). Test sample: Left-vlPFC–right dlPFC FC was positively associated with depressive cognition (β = 0.035, p = 0.061), and negatively with manic cognition (β = –0.07, p = 0.002), scores. TBS: In condition C only, pre to post decrease in TBS RE-related left vlPFC activity positively correlated with pre to post TBS ISS Activation decrease (r = 0.315; R2 = 0.09; p = 0.023). The TBS condition blind will be broken in late 2025.

Conclusions: Elevated left vlPFC activity and inverse left vlFPC-right dlPFC FC during RE are replicated mania risk-specific markers. We show feasibility of using TBS to reduce left-vlPFC activity and mania-linked symptoms to help develop new pathophysiologically-based interventions for mania and mania risk.

Disclosure: Nothing to disclose.

27.3 Generalizable fMRI biomarkers for parsing heterogeneity and predicting TMS outcomes in depression

Conor Liston

Weill Cornell Medical College, New York, New York, United States

Background: Depression is a heterogeneous syndrome driven by distinct neurobiological mechanisms in subgroups of patients that co-occur with other psychiatric diagnoses and may require different forms of treatment tailored to individual biology. Previously, we developed an approach for identifying subtypes of depression based on fMRI measures of abnormal connectivity. Here, we extend this approach to a new sample of patients with major depressive disorder (MDD) and obsessive compulsive disorder (OCD) and develop fMRI biomarkers for predicting response to accelerated intermittent theta burst stimulation (aiTBS).

Methods: In a sample of N = 224 patients with treatment resistant MDD, with and without comorbid OCD, we used regularized canonical correlation analysis with nested cross-validation to identify brain-behavior dimensions representing associations between clinical symptom profiles and functional connectivity in mood-related networks. Next, we used hierarchical clustering to delineate subtypes of MDD. Finally, we tested whether these subtypes responded differently to a 5-day course of accelerated iTBS targeting the left dorsolateral prefrontal cortex

Results: We identified four brain-behavior dimensions explaining individual differences in mood, anhedonia, anxiety, and OCD symptoms (r = 0.37–0.74 for cross-validation in held-out data, P < 0.01). Hierarchical clustering revealed four subtypes with distinct clinical symptom and aiTBS response profiles (Kruskal Wallis ANOVA, P < 0.005). Support vector machine predicted aiTBS responses based on fMRI and clinical symptom measures with 74.3% accuracy (AUC = 0.753) in cross-validation.

Conclusions: These results identify one solution to parsing and predicting heterogeneity in TMS responses and matching neuromodulation treatments to the individual patients most likely to benefit from them.

Disclosure: Delix Therapeutics, Advisory Board, Self, Brainify.AI, Advisory Board, Self

27.4 Multimodal risk markers and targeted interventions in mood disorders: insights from neuroimaging, behavioral and health registry data

Abstract Not Included

Panel

28. Complement C4 in Schizophrenia: A Multimodal Dissection of Genomics, Environment, Cortical Pruning and Age of Onset

28.1 Complement C4 gene is associated with severity, age of onset, and suicidality in schizophrenia

Abstract Not Included

28.2 Sex-specific brain structural alterations linked to C4A expression and C4 haplotypes in schizophrenia spectrum disorders

Grace Jacobs

King's College London, Institute of Psychiatry, Psychology and Neuroscience, London, United Kingdom

Background: Complement component 4 (C4) plays a key role in synaptic pruning, and both C4A expression and structural variation in the C4 gene have been implicated in schizophrenia risk. Limited neuroimaging studies thus far have linked C4A to altered cortical structure and hippocampal volume. We examined associations between C4A/B expression, C4 haplotypes, and global brain metrics in healthy adults and those with schizophrenia spectrum disorders (SSDs).

Methods: MRI and genetic data were collected from 173 participants—healthy controls (n = 82, 50 females) and individuals with SSDs (n = 91, 33 females). Freesurfer (v6.0) was used to derive global brain measures and selected a priori regions. Copy numbers of C4A, C4B, and their long (C4L) and short (C4S) forms were quantified using TaqMan assays, and predicted C4A and C4B expression levels were calculated. Linear regressions assessed associations between C4 measures and imaging metrics, controlling for sex, age, diagnosis, and intracranial volume. Group and sex interactions were also tested. Multiple comparisons were corrected for using false discovery rate (FDR).

Results: C4A/B expression and haplotypes (C4AL, C4AS, C4BL, C4BS) did not differ by diagnosis or sex. In SSDs, higher C4A expression was linked to increased right lateral ventricle volume (SB = 0.3, pFDR = 0.03). In females with SSDs, elevated C4A expression was associated with larger ventricles (SB = 0.6, pFDR < 0.04) and reduced right thalamic volume (SB = 0.6, pFDR = 0.006). Higher C4AS correlated with greater subcortical gray matter volume in females (SB = 0.6, pFDR = 0.02). Higher C4BL was linked to reduced cerebellar white matter across groups (SB = 0.2, pFDR = 0.02) and increased hippocampal volume in healthy males (SB = 1.0, pFDR = 0.04). C4BS was associated with increased hippocampal volume in SSDs (SB = 0.4, pFDR = 0.01), and smaller ventricles (SB = 1.2, pFDR = 0.006) in females with SSDs.

Conclusions: C4 expression and haplotypes did not differ by diagnosis or correspond to widespread brain alterations, consistent with prior studies. However, in SSDs, especially females, C4A expression and haplotypes were linked to volumetric differences in ventricles and subcortical areas. Findings support a role of C4, particularly C4A and long forms (C4L), in the pathophysiology of schizophrenia, with potential protective effects from short forms like C4S.

Disclosure: Nothing to disclose.

28.3 Complement component 4 and longitudinal brain development in emerging psychosis

Leanna Hernandez

Semel Institute - UCLA, Los Angeles, California, United States

Background: Genetic variation at the complement component 4A (C4A) locus is a major risk factor for schizophrenia (SZ). In the brain, C4A expression is hypothesized to influence synaptic pruning and to act in a sex-specific manner, contributing to a higher risk of SZ in males. Our prior work showed that in children, higher genetically regulated expression (GREx) of C4A is linked to temporal lobe size and increased risk for psychotic-like experiences. However, it remains unknown whether C4A expression impacts longitudinal change in brain structure across adolescence and adulthood. We addressed this gap by conducting two large-scale, multi-ancestry studies examining how C4A GREx affects the rate of cortical thinning in: 1) a population-based sample of adolescents aged 10–14, and 2) individuals at clinical high risk for psychosis (CHR-P) aged 12–34.

Methods: Data were drawn from the ABCD (N = 2334) and NAPLS2 (154 CHR-P; 74 controls) studies for both sexes. C4 haplotypes were imputed using Beagle and C4 GREx was computed using previously published weights. Cortical thickness (CT) across 34 bilateral regions was extracted from structural MRI using FreeSurfer. Rate of change (ROC) in CT was estimated using longitudinal slopes in ABCD (three timepoints) and annual percent change in NAPLS2 (two timepoints). Linear mixed-effects models tested associations between C4A GREx and CT ROC, adjusting for C4B GREx, age, sex, site, and ancestry PCs. FDR correction was applied (q < 0.05).

Results: In ABCD youth, females showed faster CT thinning relative to males, prompting sex-stratified analyses. In males, higher C4A GREx was linked to faster thinning in the superior temporal sulcus and posterior cingulate. Similarly, in CHR-P who converted to psychosis, higher C4A GREx predicted faster thinning, again in temporal and cingulate cortex, but stable or increased CT in non-converters (CHR-NC). In CHR-NC, low SZ polygenic risk buffered the effects of high C4A GREx, reducing the rate of cortical thinning in these brain regions.

Conclusions: C4A GREx influences cortical maturation in both population-based and high-risk samples, with converging effects on temporal and cingulate thinning. These findings implicate C4A-driven pruning as a mechanism of psychosis vulnerability and suggest that low schizophrenia polygenic risk may buffer this effect in resilient individuals.

Disclosure: Nothing to disclose.

28.4 Altered expression of neuro-immune regulators in schizophrenia: evidence from brain and blood transcriptomic meta-analysis and network-based approaches

Romain Rey

Le Vinatier Hospital, Lyon, France, Bron, France

Background: Schizophrenia pathogenesis may involve aberrant synaptic pruning mediated by excessive complement system activity (CSA) and altered microglial function. Microglia and CSA are tightly regulated by neuro-immune regulators (NIREGs) which are involved in regulating adverse innate response and play a critical role in the regulation of the synaptic pruning process. NIREGS have been categorized in two subgroups i) complement-NIREGs (CREGs) inhibit complement activation and thus increase the level of tissue resilience to CNS injury, and ii) don't eat me signals (DEMs) engage microglial counter receptors to maintain microglia in a homeostatic, protective phenotype. This study investigated transcriptional alterations of NIREGS in the brain and blood tissues of individuals with schizophrenia (SZ individuals) as compared to healthy controls (HC).

Methods: Meta-analyses were performed on gene expression data from 674 SZ individuals and 598 HCs in postmortem brain tissue, and 164 SZ individuals and 197 HCs in peripheral blood. In addition to C4 gene, 9 genes encoding key NIREGS were analyzed: 3 genes encoding CREGS (CD46, CD55, CD59), 3 genes encoding DEMS (CD47, CD200, CX3CL1) and a further 3 genes encoding their microglial counter-receptors (SIRPA, CX3CR1, CD200R). Exploratory network analysis was performed in brain datasets.

Results: In brain tissue, SZ was associated with C4 overexpression and reduced CD46 and CX3CL1 expression. Sex-specific differences emerged for CD200 (female-specific) and CD59, CX3CR1 (male-specific). In blood, CD46, CD55, and CD59 were overexpressed, while CX3CR1 was underexpressed. Brain and blood showed distinct altered expression patterns. However, disruption of the CX3CL1-CX3CR1 axis was observed in both. Network analyses revealed altered co-regulation between astrocytes, microglia and neurons in SZ patients.

Conclusions: This study provides evidence of an altered transcription of genes encoding CREG and DEMS in the brain and blood of SZ individuals, suggesting that immune dysregulation in schizophrenia arises from a combination of C4 overexpression and reduced expression of CREGs and DEMS. In SZ individuals, blood CX3CR1 underexpression may serve as a peripheral biomarker of the CX3CR1 CX3CL1 system disruption.

Disclosure: Nothing to disclose.

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29. Microglia at the Intersection of Neurobiology and Behavior: Insights From Preclinical Models

29.1 Microglial metabolism dysfunction restored by angiotensin converting enzyme inhibitor in a mouse model of autism spectrum disorder

Lior Brimberg

The Feinstein Institute for Medical Research, Manhasset, New York, United States

Background: Exposure in utero to maternal anti-Caspr2 antibodies disrupts microglial function and induces ASD-like phenotypes in male, but not female mice. We found increased microglial reactivity, reduced CA1 hippocampal spine density and impaired sociability in males exposed in utero to anti-Caspr2 IgG, all of which were rescued by the ACE inhibitor, captopril. scRNA-seq revealed downregulation of microglial OXPHOS pathway normalized by captopril. Here we study the consequences of altered microglial metabolism, and whether captopril acts via angiotensin II type 1 receptor (AT1R).

Methods: We used Seahorse analyzer to detect changes in microglia bioenergetics and combined transmission electron microscopy with immunohistochemistry to evaluate microglial mitochondrial morphology.

Tamoxifen inducible neuronal AT1R (AT1RfloxThy1creERT2) exposed in utero to anti-Caspr2 (“Anti-Caspr2) or control (“Control”) IgG receive tamoxifen, or vehicle (corn oil). Microglial reactivity (sholl analysis and CD68) was assessed at P35 comparing Anti-Caspr2 treated with tamoxifen (deletion of AT1R) to Anti-Caspr2 and Control mice treated with corn oil (same genotype, no AT1R deletion).

Samples sizes in each group are 6–9 Seahorse, 4–5 electron microscopy, and 3 AT1RThy1 mice. t-test, or linear mixed model analyses were performed.

Results: OCR analysis of hippocampal microglia from male Anti-Caspr2 mice revealed reduced mitochondrial respiration kinetics compared with Controls, including decreased basal, maximal, and ATP-linked respiration (p < 0.005). Extracellular acidification rates were also lower at baseline and following maximal glycolytic challenge (p < 0.05). Mitochondrial structural analysis showed increased fission and length in Anti-Caspr2 compared to Controls. Preliminary data indicate that neuronal AT1R deletion ameliorates microglial reactivity in Anti-Caspr2 mice compared to Anti-Caspr2 mice without AT1R deletion, comparable to Controls (p < 0.05).

Conclusions: Anti-Caspr2 mice exhibit impaired microglial energy metabolism, likely due to mitochondrial dysfunction. Captopril ameliorates this phenotype, likely via indirect effects on neuronal AT1R, as ACE inhibition reduces angiotensin II production and thus AT1R activation. This leads to decreased neuronal oxidative stress, mitigating microglial dysfunction.

Disclosure: Nothing to disclose.

29.2 The sex-specific role of microglial glucocorticoid receptor in the effects of early-life adversity

Jessica Bolton

Georgia State University, Atlanta, Georgia, United States

Background: Early-life adversity (ELA) is a robust predictor of neuropsychiatric disorders such as depression. It's known that ELA alters the hypothalamic-pituitary-adrenal axis, causing increased levels of corticotropin-releasing hormone (CRH) and increased threat-response behavior. We recently reported that ELA increases excitatory input onto CRH+ neurons in the paraventricular nucleus of the hypothalamus (PVN) at postnatal day (P)10 by decreasing the amount of synaptic pruning by microglia. However, the mechanisms by which ELA impairs microglial function during brain development are unknown. Here, we aim to determine the role of microglial glucocorticoid receptors (GR) in causing the effects of ELA on microglial function and later behavior.

Methods: We employed CX3CR1-Cre+::GR-fl/+ mice of both sexes to “knock down” GR expression in microglia (mGR-KD), combined with the limited bedding and nesting model for ELA. We assessed the effects of genotype, ELA, and sex on synapse number, microglial engulfment, and behavioral outcomes in each condition. For behavior, we used the looming-shadow test to measure the response to a threat, which is dependent on excitation of PVN-CRH+ neurons, as well as the elevated zero-maze to measure anxiety-like behavior.

Results: Our data reveal that mGR-KD increases the number of excitatory synapses in the P10 PVN of control males, thus mimicking ELA, but decreases their number in ELA mice (interaction of Genotype x ELA, p < 0.05, post-hoc, p = 0.1). The assessment of microglial synapse engulfment is ongoing, as well as the synapse number in females. In adults, we find that mGR-KD in Results: in a slower latency to react to a simulated predator threat in all mice except ELA females (interaction of Genotype x ELA, p < 0.05, post-hoc, p < 0.05). In the elevated-zero maze, mGR-KD renders control males less exploratory and potentially more anxious, but does the opposite in control females. ELA does not alter time spent in the open arms in males, but increases it in females, potentially indicating increased risk-taking behavior.

Conclusions: Together, our data suggest that microglial glucocorticoid receptor knockdown may have differential effects, in a sex- and stress-dependent manner. These Results: will have important implications for the development of preventative interventions and therapeutic strategies for at-risk children.

Disclosure: Nothing to disclose.

29.3 Maturation of mesolimbic circuits: critical roles for microglia and early life stress

Lindsay De Biase

University of California, Los Angeles, UCLA School of Medicine, Los Angeles, California, United States

Background: Perturbed microglial function is implicated in neurodevelopmental disorders and psychiatric illnesses that emerge in adolescence. However, there are substantial gaps in our understanding of microglial development in brain regions where dysfunction is implicated in psychiatric disorders, such as the nucleus accumbens (NAc). We showed previously that NAc microglia are overproduced during postnatal development, with peak cellular densities reached in the second and third postnatal weeks, during periods of rapid NAc synaptogenesis. These findings raise the possibility that microglia play a central role in promoting NAc synapse development as well as shaping windows of vulnerability to early life insults.

Methods: To define how microglia shape NAc synapse and circuit development, we leveraged a combination of confocal imaging, acute brain slice electrophysiology, proteomics, transcriptomics, behavioral analyses, and fiber photometry in mice that lack microglia as well as mice that experienced early life stress via limited bedding and nesting (LBN) from postnatal (P)4 to P11. Both male and female mice were used for all analyses.

Results: In mice that lack microglia, we found blunted NAc excitatory synapse formation. Tissue-level NAc proteomics confirmed that microglial absence impacted numerous proteins involved in synaptic function and also identified candidate microglial-derived synaptogenic cues. Finally, microglial absence caused lasting impact on threat avoidance behavior and NAc neuronal activity in adulthood. Following early life stress, NAc microglial density was elevated in LBN P12 and P22 pups and RNAseq analysis revealed that candidate microglial synaptogenic molecules were altered by early life stress. Moreover, NAc microglia from P70 LBN and control mice exhibited more than 2000+ differentially expressed genes, including essential regulators of microglial identity, synaptic interactions, and inflammatory responses.

Conclusions: Together, these results indicate a critical role for microglia in regulating the synaptic landscape of the developing NAc and provide valuable datasets for guiding follow-up work to identify molecules that may link early life stress, altered microglial function, and lasting perturbation of NAc circuit function.

Disclosure: Nothing to disclose.

29.4 Loss of microglial TNFα impairs synaptic plasticity in the prefrontal cortex and causes cognitive deficits

Eric Wohleb

University of Cincinnati College of Medicine, Cincinnati, Ohio, United States

Background: Seminal studies demonstrate that glial-derived cytokines, such as tumor necrosis factor (TNF)-α, are important for homeostatic synaptic plasticity and regulate complex behaviors. Our recent work shows that chronic stress reduced Tnfa expression in microglia isolated from the prefrontal cortex (PFC) and this was linked to synaptic loss and behavioral consequences in male mice. Interestingly, female mice did not show altered microglial Tnfa expression or related synaptic or behavioral effects. Despite these findings, no studies have determined if loss of microglial TNFα affects the structure and function of PFC neurons and associated behaviors.

Methods: Male and female mice with tamoxifen-inducible, microglia-specific Tnfa depletion (Cx3cr1CreERT2: Tnfafl/fl) and genotype controls (Cx3cr1CreERT2: Tnfa + /+) were exposed to 14 days of chronic unpredictable stress (CUS) or handled intermittently as controls. Endpoints included molecular analyses of microglia, immunohistology for synaptic density, brain slice electrophysiology to measure neuron excitability, and assessments for behavior and cognitive function.

Results: Male and female mice had physiological responses to CUS with reduced weight gain. Interestingly, mice lacking microglial Tnfa also showed no weight gain (sans CUS). Flow cytometry and cell sorting of PFC microglia confirmed Tnfa depletion, and showed that microglia lacking Tnfa had altered expression of cell surface markers P2Y12 and CSF1R. The systemic AAV(PHP.eB)-hSyn1-tdTomato was used to fill neurons and assess dendritic structures. In both males and females, we found that loss of microglial Tnfa reduced spine density in the PFC. This effect was not exacerbated following CUS exposure. Additional studies using patch-clamp electrophysiology revealed that PFC pyramidal neurons in mice lacking microglial Tnfa had diminished measures of excitability. Consistent with these neurobiological effects, microglial Tnfa depletion in both male and female mice impaired discrimination in temporal object recognition. These deficits were comparable to those observed in male, but not female, mice exposed to CUS.

Conclusions: These studies demonstrate that microglia-derived TNFα supports synaptic plasticity in the PFC and loss of microglial TNFα leads to diminished synaptic function and cognitive deficits.

Disclosure: Nothing to disclose.

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30. Appetite for Addiction: Neural Commonalities in Food and Drug Disorders

30.1 Neuroinflammation in the orbitofrontal cortex and goal directed behaviour

Stephanie Borgland

Hotchkiss Brain Institute, University of Calgary, Calgary, Canada

Background: Despite strong motivation to lose weight, most people with obesity return to old behaviours within months of being on a weight-loss diet and regain any weight that was lost. One explanation is that these behaviours become inflexible and habitual. The orbitofrontal cortex (OFC) is important for decision making and dysfunction of the OFC can lead to habit-based behaviours. Disinhibition of the OFC and obesity leads to an impairment in goal directed behaviour. Astrocytes normally supply nutrients to neurons and regulate synaptic function but can become ‘reactive’ in inflammatory situations, such as obesity. However, it is unknown if low grade inflammation that occurs with obesity influences astrocyte function and ultimately goal-directed behaviours.

Methods: We used a 12-week high fat diet (HFD) exposure or a model of excitatory DREADD (AAV2/3-GFA1abcd-hDM3q) activation in lateral OFC astrocytes using 2 weeks of DCZ in the drinking water to examine inflammatory markers and cytokine expression in the lOFC as well as the effects on goal-directed behaviour using a contingency degradation model.

Results: Obesity significantly increased the number of S100b-expressing astrocytes (t(29) = 3.46, P = 0.0017) and intensity ((t(29) = 2.96, P = 0.0061) compared to the chow diet. Similarly, chronic astrocyte activation increased the number S100b-expressing astrocytes (t(38) = 2.07, P = 0.04), and the intensity (t(39) = 3.56, P = 0.001). A multiplex cytokine panel revealed increases sex differences in lOFC cytokine expression with males exhibiting increased pro-inflammatory MCP-1 (t(11) = 2.3, P = 0.04), and a decrease in anti-inflammatory IL-4 (t(12) = 2.46, P = 0.03) and IL-2 (t(11) = 2.45, P = 0.03). Female obese mice had increased GM-CSF (t(9) = 4.37, P = 0.0018, MIP-2 (t(11) = 2.75, P = 0.02), and TNFa (t(10) = 2.57, P = 0.02) in the lOFC. Chronic astrocyte activation also increased TNFa (t(8) = 2.4, P = 0.04), IL-7 (t(8) = 2.38, P = 0.04), and MCP-1 (t(8) = 3.2, P = 0.01) in the OFC. Acute lOFC astrocyte activation did not alter goal-directed behaviour. Chronic lOFC astrocyte activation increases weight gain.

Conclusions: Diet induced obesity or chronic astrocyte activation induces inflammatory markers within the OFC. These changes may underlie impaired goal-directed behaviour observed in obesity.

Disclosure: Nothing to disclose.

30.2 Elevated cocaine demand after binge sucrose or saccharin: link to increased orexin/hypocretin signaling in ventral tegmental area

Gary Aston-Jones

Brain Health Institute, Rutgers University, Piscataway, New Jersey, United States

Background: Binge eating disorder is the most common eating disorder but the underlying neuronal mechanisms are not known. The orexin/hypocretin (Ox) brain neuropeptide system is strongly associated with both addiction-like behaviors and food intake. This study examined a contribution of Ox signaling to binge eating behavior, and tested a common Ox mechanism for interactions between binge eating- and addiction-like drug consumption.

Methods: Four groups of female rats were used: (i) intermittent access (IA; 12h/d) to 10% sucrose and food (n = 13), (ii) IA to 0.4% saccharin and food (n = 13), (iii) IA to food (n = 12) or (iv) continuous access to both food and sucrose (n = 13). All access treatments were for 28d. We focused on females as their binge behavior is much stronger.

Results: Sucrose or saccharin IA animals displayed excessive intake in the first hr (i.e., binge eating behavior), as expected (p = 0.0001 and 0.0029). Notably, animals with 28d of sucrose or saccharin consumption had more orexin neurons (by immunohistochemistry) compared to food-only controls (p = 0.0001 and 0.0001).

In addition, the Ox-1 receptor antagonist SB334867 (SB, n = 19), or the dual Ox receptor antagonist suvorexant (n = 12), reduced binge-like intake in rats with sucrose (p = 0.0027 and 0.03) or saccharin IA (p = 0.006 and 0.003). Inhibition of Ox projections to ventral tegmental area (VTA) using a retrograde Dio-hM4Di AAV in orexin-cre+ rats decreased binge-like intake in sucrose (p = 0.02) or saccharin IA groups (p = 0.007), indicating that VTA is involved.

We also assessed whether binge-like consumption altered economic demand for cocaine. We found that sucrose or saccharin IA increased demand for cocaine. SB (10 or 30 mg/kg ip), or hM4Di inhibition of orexin inputs to VTA, decreased demand for cocaine in sucrose (SB p = 0.02 and hM4Di p = 0.0001 or saccharin binge groups (SB p = 0.01 and hM4Di p = 0.0001).

Conclusions: Our findings indicate that chronic sucrose or saccharin consumption increased the number of Ox-expressing neurons, as previously reported for drugs of abuse. The results highlight elevated Ox signaling in VTA as a mechanism underlying the increased binge behavior and drug demand after sucrose or saccharin IA. Our results support addiction-like properties of highly palatable food, and indicate that elevated Ox signaling may underlie aberrant food and drug consumption behaviors.

Disclosure: Nothing to disclose.

30.3 A Biological basis for binge eating as ‘self-medication’: an orexin/hypocretin circuit links dysphoria to excessive eating

Morgan James

University of Sydney, Camperdown, Australia

Background: In binge eating disorder (BED), over 90% of episodes are triggered by negative mood, yet the role of negative reinforcement in driving excessive food intake remains understudied. Here, using rats, we developed a novel model of obesity-induced dysphoria; we then asked if this negative mood state predisposes to, and is ameliorated by, binge-like eating. We also tested how this ‘self-medicating’ pattern of eating engages the orexin-ventral tegmental area (VTA) circuit, a known mediator of motivated behaviors.

Methods: BED is twice as prevalent in women; thus we utilized Female Long Evans rats. Diet-induced obesity (DIO) was induced by maintaining rats on a high fat diet (45% fat) for 8w; control rats (‘lean’) were fed chow. Both groups were given intermittent, limited access to a sweetened fat solution over a subsequent 4w period ('binge'). Reward behavior was assessed using intracranial self-stimulation (ICSS; n = 7–8/grp) and social interaction assays (n = 8/grp). To evaluate addiction-relevant phenotypes, we measured sucrose demand, persistence of responding for sucrose, and cue-induced reinstatement of extinguished sucrose seeking (lean n = 16; DIO n = 20). Real-time orexin signaling in VTA was monitored using fiber photometry with the OxLight1 sensor (n = 5–6/grp). In a separate DIO cohort (n = 17), we used chemogenetic inhibition to suppress orexin neuron activity and examined effects on binge intake and addiction behaviors.

Results: DIO rats had higher ICSS thresholds (p = 0.035) and lower social preference (p = 0.001). DIO rats also exhibited greater escalation of binge-like eating (linear regression, p = 0.041), which partially normalized ICSS thresholds (p = 0.032) and social preference (p = 0.054), and promoted higher ‘food addiction’ behaviors (p’s < 0.042). In lean rats, food-associated stimuli elicited orexin signaling in VTA as measured by OxLight1 signal; this was blunted in HFD rats but partially restored by binge (p = 0.045). Chemogenetic inhibition of orexin neurons reduced binge eating (p = 0.045) and 'food addiction' behaviors (p's < 0.05).

Conclusions: Binge eating can be 'self-medicating' against dysphoric states. The negatively reinforcing properties of binge eating contribute to the development of 'food addiction' behaviors, in part due to engagement of an orexin-VTA circuit, creating a 'vicious cycle' of uncontrolled eating.

Disclosure: Johnson and Johnson, Stock / Equity - Publicly Traded Company, Spouse/Partner

30.4 Feasibility and preliminary efficacy of N-acetylcysteine for loss of control eating: an open label study

Robyn Brown

University of Melbourne, University of Melbourne, Australia

Background: Loss of control is a core feature of both substance use disorder and eating disorders such as binge eating disorder and bulimia nervosa. N-acetylcysteine (NAC) has been shown to restore striatal glutamatergic dysfunction in preclinical models of cocaine relapse and reduce some compulsive behaviors in humans. We have observed striatal glutamatergic dysfunction in preclinical models of disordered overeating. As such we wished to evaluate the feasibility and preliminary efficacy of NAC for loss of control eating in humans.

Methods: A single site open label study involving community residents in Australia was conducted between Jan 2023 and Oct 2024. A total of 36 participants with loss of control eating were enrolled. Participants received oral NAC medication (2400 mg/day) for 12 weeks. Treatment outcomes were assessed comparing the 12 week timepoint to baseline using both retrospective questionnaires (paired t-test) and ecological momentary assessment (EMA, generalized linear mixed model for binomial distribution). The primary outcome was feasibility (recruitment rate, retention rate at week 12, adherence to medication). The secondary outcome was change in loss of control eating from baseline to week 12. Changes in drivers of eating behavior as a result of NAC treatment were also explored.

Results: Recruitment rate was 1.7 participants per month; retention rate was 91% and medication adherence was 93%. Mean frequency of loss of control eating decreased between pre- and post-NAC treatment from 14.2 to 5.0 (95% CI: 5.8 to 12.5) while the severity of loss of control eating decreased from 6.6 to 3.6 (95% CI: 2.2 to 3.6). Food craving decreased from 2.79 to 2.18 (95% CI: 0.43 to 0.78); emotional eating decreased from 50.21 to 32.93 (95% CI: 10.31 to 24.23), coping motive score decreased from 13.06 to 10.42 (95% CI: 1.15 to 4.12), and preoccupation with food decreased from 10.73 to 5.70 (95% CI: 3.61 to 6.44).

Conclusions: Our data show that delivering a 12-week NAC intervention in people with loss of control eating and conducting behavioral assessments using EMA is feasible. This pilot study provides a rationale for conducting a randomised controlled trial to determine the efficacy of NAC for compulsive eating.

Disclosure: Nothing to disclose.

Panel

31. Beyond the Trip: Rethinking Psychoplastogens for Neurological Disorders

31.1 Hydroxynorketamine as a therapeutic candidate for Alzheimer’s disease: preclinical insights and mechanistic evidence

Abstract Not Included

31.2 Targeting synaptic loss in Parkinson’s disease depression with ketamine

Sophie Holmes

Yale University, New Haven, Connecticut, United States

Background: Depression is highly common in Parkinson’s disease (PD) and associated with increased disability and accelerated disease progression. But serotonergic-based antidepressants have limited efficacy for PD depression, and there has been little progress in understanding its pathology or evaluation of new treatments. We hypothesize that PD-related pathology in mood-related circuitry underlies depression in PD, and that this can be targeted by plasticity-enhancing interventions like ketamine.

Methods: We measured synaptic density (using [¹¹C]UCB-J PET) and network organization (using fMRI) in PD patients with depression (n = 10), without depression (n = 20), and HCs (n = 18). In a separate clinical trial, 50 PD patients with depression are randomized to receive six infusions of either ketamine or placebo. A subset of patients (13 per arm) have undergone pre- and post-treatment imaging with [¹¹C]UCB-J PET and fMRI. As of June 2025, 47 patients have completed the trial, with 3 patients currently undergoing study treatment; the trial is on track for completion and unblinding by August 2025.

Results: PD depression patients showed significantly lower synaptic density in mood-related regions—including the dlPFC, ACC, amygdala, and hippocampus—compared to both non-depressed PD and healthy controls (all p < 0.05). Lower synaptic density in the dlPFC, amygdala, and hippocampus was associated with greater depression severity (all p < 0.05). Functional connectivity was reduced within the default mode and fronto-limbic networks in PD depression. In the clinical trial, of the 47 completers to date, 55% met criteria for treatment response and 38% for remission. Breakdown by treatment arm will be available following unblinding in August 2025. Ketamine has been well tolerated, with no serious adverse events.

Conclusions: Our mechanistic work and initial safety data implicate ketamine as a targeted, safe, and well-tolerated intervention in PD. With enrollment and unblinding scheduled for completion by August 2025, we will present the first RCT evidence of ketamine’s clinical efficacy and mechanistic effects in a neurodegenerative disease. Findings may position ketamine as a mechanistically-informed antidepressant for PD and provide a broader framework for targeting synaptic dysfunction in neuropsychiatric symptoms of neurodegenerative disease.

Disclosure: Nothing to disclose.

31.3 Psilocybin treatment of mild head injury promotes hyperconnectivity and BDNF signaling

Craig Ferris

Northeastern University, Boston, Massachusetts, United States

Background: There is an expanding literature on the behavioral and neurobiological consequences of repetitive mild head injuries that incur while playing organized sports, car accidents, falls in the elderly, or in active military service. Repetitive mild head impacts increase the risk of dementia, Parkinson’s disease, and Alzheimer’s. There is no FDA approved treatment for repetitive mild head injury. We hypothesized psilocybin (PSI) with it effects on neuroplasticity could be used these head injuries.

Methods: Adult female (N = 24) Wistar rats were divided into three experimental groups (n = 8; determined by a priori power analysis): 1) healthy sham controls injected with saline vehicle but given no head impact (Sham-VEH), 2) head-impacted and injected with saline vehicle (Hit-VEH), and 3) head-impacted and injected with PSI (Hit-PSI). Rats were impacted while fully awake and during the active period of their circadian cycle. Rats were head impacted once each day for three consecutive days. After each head impact they were treated IP with 3.0mg/kg psilocybin. Over the following two weeks they were evaluated for changes in vasogenic edema, vascular reactivity, gray matter microarchitecture and resting state functional connectivity using MRI. Data were registered to a rat 3D MRI atlas with 173 brain regions providing site-specific differences in global brain structure and functional connectivity between head impacted and sham controls. Postmortem samples from the forebrain were assayed for BDNF, phosphorylated tau, TrkB, and gliosis.

Results: PSI treatment reduced global brain edema. PSI normalized altered vascular reactivity, particularly in the basal ganglia, prefrontal cortex, and olfactory regions. Functional connectivity analysis demonstrated global hypoconnectivity post-injury, matching clinical observations in head-injured patients. PSI treatment induced dramatic hyperconnectivity, notably in dopaminergic pathways to thalamic and somatosensory regions. Protein analysis showed an increase in BDNF and TrkB and reduction in tau phosphorylation.

Conclusions: This translational model successfully bridges bench-to-bedside by replicating clinical observations and identifies PSI as a promising therapeutic agent for repetitive mild head injury and its neurodegenerative consequences.

Disclosure: Ekam Imaging, Founder, Self

31.4 Psilocybin therapy for mood dysfunction in Parkinson's disease: an open-label pilot study

Abstract Not Included

Mini Panel

32. Integrating Clinical/Genetic, Digital Phenotyping, and Stem Cell Models to Understand the Long-Term Course of Bipolar Disorder

32.1 Large-scale characteristics of clinical course of bipolar disorder

Martin Alda

Dalhousie University, Halifax, Canada

Background: Bipolar disorder (BD) has been variably described as a recurrent/episodic or chronic condition. This ambiguity could reflect the heterogeneity of the illness, possibly influenced by other external factors (treatment impact, comorbid conditions or early trauma).

Methods: We studied a cohort of 799 patients with BD followed longitudinally. The patients were diagnosed according to DSM-IV criteria. Their initial assessments were based on SADS-L or SCID interviews that were subsequently reviewed in a blind fashion by a panel of expert clinical researchers. Details of clinical course, symptom profiles, comorbid conditions were obtained from interviews, OPCRIT, and medical records. Family history was collected by a combination of direct interviews of relatives and FH-RDC. Following bi-variate analyses of data, we conducted polychotomous logistic regression with type of clinical course as dependent variable, and factor analysis of clinical profiles using principal component method.

Results: The sample includes 313 men and 486 women in the sample, their age at the last assessment was 45.1+/− 15.0 years, the illness duration was 20.7+/− 13.5 years. 549 were diagnosed with BD type I and 250 with BD type II. Their clinical course was classified as episodic with full symptomatic and functional recovery between episodes (n = 311), episodic with residual symptoms and/or incomplete functional recovery (n = 237) or chronic (n = 251). The three groups differed significantly with respect to a number of variables (BD subtype, age at onset, predominant polarity, long term lithium response, family history of BD, and comorbid conditions), all p < 0.001. In all comparisons the episodic group with residual symptoms fell in between the fully episodic and chronic groups. In logistic regression, episodic course was associated with BD I diagnosis and manic predominant polarity, low rates of comorbidity with generalized anxiety disorder (GAD) and obsessive-compulsive disorder (OCD), and family history of bipolar disorder. Factor analysis yielded 6 factors (F1: diagnosis-polarity-psychotic symptoms; F2: social anxiety and GAD; F3: clinical course and family history; F4: panic disorder and OCD; F5: sex and age at onset; F6: substance abuse).

Conclusions: These results support the conjecture that patients with episodic clinical course are a subtype of BD with stronger genetic predisposition and better outcome of long-term treatment with lithium. Further research should examine these differences at a genomic level.

Disclosure: Nothing to disclose.

32.2 Trajectories of suicidal risk impact mood regulation differently in patients with a diagnosis of bipolar disorder

Abigail Ortiz

University of Texas Southwestern, Dallas, Texas, United States

Background: Bipolar disorder (BD) carries a suicide risk 20 times higher than the general population, with up to 60% of patients attempting suicide at least once in their lifetime. Traditional monitoring methods have failed to capture rapid mood fluctuations preceding suicide attempts, limiting effective prevention strategies. We hypothesized that quantifiable differences in mood regulation would emerge across the suicidality continuum, with high-risk participants showing distinctive patterns compared to low-risk participants.

Methods: Our longitudinal study included 164 patients with BD. Participants self-reported daily mood, anxiety, and energy levels using an electronic visual analog scale, generating 64,351 valid observations (79.22% compliance) over 461.5 ± 236.6 days. We stratified participants into six hierarchical risk groups (i.e., from lowest to highest risk): (1) no history of suicidality, euthymic; (2) history of suicidality, euthymic; (3) no history of suicidality, depressed, not actively suicidal; (4) history of suicidality, depressed, not actively suicidal; (5) no history of suicidality, depressed, actively suicidal; and (6) history of suicidality, depressed, actively suicidal.

Results: Autocorrelation analysis revealed significantly elevated day-to-day coefficients in the highest-risk group compared to the lowest-risk group across all parameters: mood (0.53 vs. 0.29, p = 0.011), energy (0.52 vs. 0.23, p = 0.029), and anxiety (0.55 vs. 0.32, p = 0.049). Notably, even when euthymic, participants with prior suicidality exhibited higher autocorrelation coefficients than those without such history (p > 0.05).

Cross-correlation analyses demonstrated significant mood-energy decoupling during depressive episodes among actively suicidal participants. Mood-anxiety dynamics showed significantly stronger negative correlation in depressed participants with prior suicide attempts but not actively suicidal (−0.52) compared to those without prior attempts (−0.37, p = 0.023).

Conclusions: Our findings challenge traditional views that equate euthymia with absence of suicide risk, suggesting persistent neurobiological vulnerability despite symptomatic remission. This study underscores the importance of capturing dynamic mood regulation processes to improve prediction and prevention of suicidal behavior in BD.

Disclosure: Nothing to disclose.

32.3 Modeling the cellular trajectories of bipolar disorder using patient-derived neurons: from hyperexcitability to treatment response

Anouar Khayachi

McGill University Faculty of Medicine, Montreal, Canada

Background: Bipolar Disorder (BD) is a complex and recurrent psychiatric illness characterized by heterogeneous long-term clinical trajectories. Although lithium (Li) remains the most effective mood stabilizer, its mechanisms of action are still not fully understood, and only a subset of patients respond to treatment. To investigate the cellular basis of BD chronicity and treatment response, we employed an in vitro model using induced pluripotent stem cell (iPSC)-derived neurons from patients with BD.

Methods: We studied iPSC-derived neurons from BD patients clinically classified as lithium responders (LR) or non-responders (LNR), as well as control individuals. Neurons were maintained in culture and analyzed longitudinally over an 11-week period. A multimodal approach, combining electrophysiology, calcium imaging, transcriptomics, phosphoproteomics, and biochemistry was used to explore the mechanisms underlying neuronal hyperexcitability and pharmacological response.

Results: We observed a persistent neuronal hyperexcitability phenotype in BD-derived neurons over time in culture. Lithium selectively reversed this phenotype in LR neurons, associated with changes in Na⁺ conductance. Transcriptomic analyses revealed altered expression of genes related to glutamatergic transmission, ion transport, and cell signaling pathways. Notably, activation of Akt signaling mimicked the effects of lithium in LR neurons, while activation of AMP-activated protein kinase (AMPK) normalized hyperactivity in both LR and LNR neurons, indicating potential for broader therapeutic application. These findings suggest that distinct molecular mechanisms may underlie different BD trajectories and treatment responses.

Conclusions: This study demonstrates that patient-derived neuronal models can recapitulate persistent pathophysiological features of BD, allowing for the exploration of disease mechanisms over time. By integrating functional and molecular profiling with pharmacological responsiveness, our findings provide novel insights into the cellular correlates of illness trajectories and support the development of precision-targeted treatments beyond lithium.

Disclosure: Nothing to disclose.

Study Group

33. Identifying and Filling the Gaps Between Evidence-Based and Real-World Use of Ketamine Related Treatments in Mental Health

Gerard Sanacora, Joseph Goldberg, Sandhya Prashad, Cristina Cusin, Balwinder Singh, James Murrough

Yale University, New Haven, Connecticut, United States

Study Group Summary: Ketamine provides one of the clearest examples of translational neuroscience impacting mental health care. Preclinical work identifying novel cortical circuits involvement in the pathophysiology of major depressive disorder and rodent studies demonstrating the glutamatergic system as a viable target for drug development led to a small clinical trial of ketamine for the treatment of depression over a quarter century ago. Since the publication of the seminal paper showing the results of that study suggesting ketamine possesses rapid onset antidepressant effects in humans, the use of ketamine has continued to grow in clinical settings worldwide. However, due to a unique set of circumstances (including; previous FDA approval of ketamine for non-psychiatric treatments, complexity of treatment delivery protocols, and FDA mandated restrictions on research with the drug) the later stages of clinical translation have proven complex and challenging for ketamine related treatments. The variability in how the treatment is employed in real-world settings, the lack of well-controlled data on the safety and efficacy of the various forms through which ketamine treatment is delivered clinically, and the inability to effectively track and monitor it’s use in clinical settings has caused many to raise concerns about the actual effectiveness and safety of the treatment.

This study group aims to briefly present data highlighting what evidence is currently available on the use, effectiveness and safety of ketamine related treatments for mental health disorders. Dr. Sanacora will discuss 5 year follow up data on the use and safety of the FDA approved esketamine nasal spray covering over 58 thousand individual patients, 37,863 patient-years of exposure, and more than 1.4 million treatment session that were recorded under the mandated Risk Evaluation and Mitigation Strategy. Dr. Goldberg will present the results of a recent Delphi consensus study of ketamine experts completed by the ASCP. The report identifies several areas where strong consensus could be reached surrounding the treatment but many other areas where descensus remains high. Dr. Prashad will present data reflecting the practice patterns of the over 400 members of the American Society of Ketamine Physicians, Psychotherapists and Practitioners. Dr. Cusin will provide data from MGB health system showing the outcomes of patients being treated with both ketamine and esketamine nasal spray and the relative success of switching between the two treatments in a real-world clinical setting. Dr. Singh will discuss the first real world study examining changes in suicidality-related healthcare utilization following initiation of ketamine or esketamine nasal spray for treatment-resistant depression, using a 6-month mirror image design. The results demonstrate a significant reduction in emergency department visits for suicidal ideation and total suicidality-related visits following the acute treatment phase, regardless of treatment type or maintenance status. Lastly, Dr. Murrough will outline the current spectrum of diagnoses clinicians target with ketamine and facilitate a discussion with the audience around the available data for these approaches, and consider their relative risks and benefits.

Dr Zarate will facilitate the group discussion and audience participation.

Disclosure: Actinogen Medical,, Consultant, Self, Alto Neuroscience,, Consultant, Self, Atai,, Consultant, Self, Axsome Therapeutics,, Consultant, Self, Biogen, Consultant, Self, Biohaven Pharmaceuticals, Boehringer Ingelheim International GmbH, Bristol-Myers Squibb, Clexio, Daiichi Sankyo, Denovo Biopharma, EMA Wellness, Douglas Pharmaceuticals, Embark, Engrail Therapeutics, Freedom Biosciences, Gilgamesh, Holmusk, Intra-Cellular Therapies, Janssen, Levo therapeutics, Lundbeck, Merck, MiCure, Navitor Pharmaceuticals, Neumora Therapeutics, Neurocrine, Newleos Therapeutics, Novartis, Noven Pharmaceuticals, Otsuka, Perception Neuroscience, Praxis Therapeutics, Relmada Therapeutics, Seaport Therapeutics, Sage Pharmaceuticals, Seelos Pharmaceuticals, Supernus, Taisho Pharmaceuticals, Tetricus, Transcend Therapeutics, Usona Institute, Valeant, Vistagen Therapeutics, and XW, Advisory Board, Self, Biohaven Pharmaceuticals, Stock / Equity - Publicly Traded Company, Self, Boehringer Ingelheim International GmbH,, Advisory Board, Self, Bristol-Myers Squibb,, Consultant, Self, Clexio,, Consultant, Self, Daiichi Sankyo,, Consultant, Self, Embark,, Advisory Board, Self, Engrail Therapeutics,, Consultant, Self, Freedom Biosciences,, Advisory Board, Self, Freedom Biosciences,, Stock / Equity - Privately Held Company, Self, Gilgamesh,, Consultant, Self, Holmusk,, Advisory Board, Self, Intra-Cellular Therapies,, Consultant, Self, Merck,, Consultant, Self, Merck, Contracted Research, Self, Freedom Biosciences, Patent, Self, Neumora Therapeutics,, Consultant, Self, Neurocrine,, Consultant, Self, Newleos Therapeutics,, Advisory Board, Self, Novartis,, Consultant, Self, Otsuka,, Consultant, Self, Relmada Therapeutics,, Advisory Board, Self, Seaport Therapeutics,, Advisory Board, Self, Sage Pharmaceuticals,, Consultant, Self, Seelos Pharmaceuticals,, Consultant, Self, Supernus,, Consultant, Self, Tetricus,, Advisory Board, Self, Transcend Therapeutics,, Advisory Board, Self, Usona Institute,, Consultant, Self, Usona Institute,, Contracted Research, Self, Tetricus,, Stock / Equity - Privately Held Company, Self, Newleos Therapeutics, Stock / Equity - Privately Held Company, Self, Lilly, Consultant, Self, Abbvie, Consultant, Self

Mini Panel

34. Social Neuropsychopharmacology: Pharmacological Investigation of Social Behavior From Mouse to Human

34.1 Endocannabinoid signaling in the control of social behavior

Abstract Not Included

34.2 How familiarity with a conversation partner affects social connection and self-disclosure after MDMA

Hanna Molla

University of Chicago, Chicago, Illinois, United States

Background: MDMA is known as an empathogen. Its empathogenic effects are thought to contribute to its effectiveness in MDMA-assisted therapy for treating psychiatric conditions via the therapeutic alliance between the therapist and the patient. An important feature of MDMA assisted therapy involves preparatory sessions designed to build familiarity and trust between the patient and therapist before MDMA administration. However, little is known about the role of familiarity in responses to the drug. This study examined whether the familiarity of a conversation partner influences the effects of MDMA on social connection and self-disclosure during a dyadic conversation with a stranger.

Methods: In a randomized, double-blind, 4-session crossover design, healthy adults (N = 33, 17 male, 16 female) engaged in 15-minute conversations with either a familiar or unfamiliar partner following administration of MDMA (100 mg) or placebo. Familiarity was established before the drug was administered, by a conversational procedure known to induce feelings of closeness between two strangers.

Results: As expected, MDMA increased ratings of closeness (p = 0.005) and connection (p = 0.02) to conversation partners relative to placebo. Linguistic analysis of the conversations showed that MDMA increased the use of affect related words (p = 0.003), and the first person pronoun ‘I’ (p < 0.001) compared to placebo. Notably, this effect was significantly greater when conversations were held with familiar partners. Conversations with MDMA and a familiar partner contained the most personal mental health related words (e.g., depressed, trauma) relative to all other conditions (familiarity x drug interaction, p = 0.04).

Conclusions: These results confirm previous findings that MDMA enhances feelings of interpersonal connection and expressions of emotion related content, but adds to this that the familiarity of the partner further enhances language related to mental health experiences. This supports the idea that familiarity, or bonding, between therapist and patient could optimize the effects of the drug in a therapeutic setting.

Disclosure: Nothing to disclose.

34.3 Opioid modulation of social connectedness in schizophrenia

Anya Bershad

UCLA, Los Angeles, California, United States

Background: Impaired social motivation is a negative symptom of schizophrenia and can result in social disconnection and the many health consequences associated with such isolation. Despite this, there are no efficacious pharmacologic treatments for this symptom. One potential target for treatment of impaired social motivation is the opioid system. Both the mu-opioid system and the kappa-opioid system have been shown to mediate social behavior in preclinical models. Buprenorphine is a unique opioid drug that acts both as a mu partial agonist and kappa antagonist, and thus has the potential to target deficits in social motivation and facilitate social connectedness. Despite this promise, the effects of low-dose buprenorphine on social motivation have not been tested in individuals with schizophrenia.

Methods: Here we report the preliminary results of an ongoing study testing the effects of a low dose of buprenorphine (0.15mg) on social motivation in socially disconnected participants with schizophrenia (planned N = 30; 15 female, 15 male). In this double-blind, cross-over, placebo-controlled trial, participants attended two laboratory sessions, receiving either placebo or buprenorphine. During expected peak drug effect, they participated in a semi-structured social encounter with a laboratory confederate during which measures of interpersonal connection and behavioral synchrony were collected.

Results: Low-dose buprenorphine was well-tolerated by the participants, and in several cases, indistinguishable from placebo. The study is ongoing, though preliminary analyses suggests buprenorphine increased ratings of how enjoyable participants felt the conversation was and how close they felt with their conversational partner, compared to placebo.

Conclusions: The results of this study suggest a role for the opioid system in mediating social motivation and lay the foundation for larger-scale clinical trials investigating buprenorphine as potential adjunct to psychosocial treatments for social deficits in schizophrenia.

Disclosure: Nothing to disclose.

Panel

35. Deep Diving Into the Neural Depths: Charting the Habenula’s Role in Substance Use Disorders

35.1 Multiomic spatial mapping of the human habenula reveals molecularly distinct and topographically organized cell types

Kristen Maynard

Lieber Institute for Brain Development, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States

Background: The human habenula (Hb) is a critical integration center governing motivated behavior and affective states. While this epithalamic region has emerged as a promising therapeutic target for neuropsychiatric disorders, little is known about the spatiomolecular organization of human Hb cell types. Anatomically, the Hb is divided into medial (MHb) and lateral (LHb) subdivisions with distinct projections to downstream targets. Rodent studies have shown spatial, molecular, and functional heterogeneity across LHb and MHb neurons, but whether these cell types are conserved in the human brain has not yet been investigated.

Methods: We used the 10x Genomics Visium, VisiumHD, and Chromium Single Cell Multiome ATAC + Gene Expression platforms to generate a comprehensive spatiomolecular map of the human Hb at cellular resolution from healthy adult control donors. For multiome, we sequenced 18,000 Hb neurons (n = 10 donors) and performed joint clustering using weighted nearest neighbors to identify 13 cell type clusters. For Visium, we profiled 12 tissue sections across the Hb anterior-posterior axis (subset of 3 donors) and implemented unsupervised spatial clustering to identify MHb and LHb spatial domains. For VisiumHD, we profiled 10 tissue sections (subset of 5 donors) and spatially localized individual cell types.

Results: Using multiome, we identified 6 LHb populations and 3 MHb populations, including CHAT-expressing cholinergic neurons enriched in OPRM1 encoding the mu opioid receptor. Visium revealed transcriptionally unique Hb spatial domains differentially enriched in MHb and LHb cell subtypes. VisiumHD spatially localized cholinergic neurons and CCK-expressing populations across the dorsal-ventral axis of the MHb. We found cross-species conservation with rodent Hb cell types and demonstrated the enrichment of neuropsychiatric and substance use disorder gene sets in specific Hb cell types and spatial domains.

Conclusions: We provide the first molecular neuroanatomical atlas of the human Hb and define spatially organized and molecularly distinct MHb subtypes conserved across species that are relevant for opioid addiction. Finally, we provide novel insights into how genes associated with psychiatric disorders and addiction map to MHb subregions and cell types.

Disclosure: Nothing to disclose.

35.2 Homeostatic scaling of opioid signaling in medial habenula

Kirill Martemyanov

University of Miami, Miami, Florida, United States

Background: The endogenous opioid system provides powerful control over emotions, nociception, and motivation among many other fundamental nervous system functions. Its major components include a panel of opioid peptides that activate four canonical inhibitory opioid receptors. However, its regulatory principles are not fully understood including the existence of additional receptors and other elements.

Methods: We used molecular screening techniques, cell biological assays for studying receptor activity, pharmacological and radioligand binding assays, electrophysiology and optophysiology to define impact of receptor signaling on physiology of medial habenula neurons.

Results: In this study we report the identification of a new receptor for the opioid peptide dynorphin. By conducting a screen of a custom library of neuropeptides, we found that orphan receptor GPR139 binds to and is activated by a series of dynorphin peptides. Unlike other opioid receptors, GPR139 couples to Gq/11 and avoids □-arrestin, providing excitatory signaling that homeostatically scales the inhibitory response of neurons to dynorphin.

Conclusions: We introduce GPR139 as a non-canonical dynorphin receptor as an essential component of the opioid system in medial habenula and beyond.

Disclosure: Evodenovo, Stock / Equity - Privately Held Company, Self

35.3 Opioid-sensitive habenular neurons: key regulators of negative affect

Emmanuel Darcq

INSERM, Strasbourg, France

Background: The mu opioid receptor (MOR) is highly involved in hedonic homeostasis, and the rewarding and negative emotional states linked with opioid use. While the implication of MOR in aversive states is demonstrated, the role of MOR-expressing neurons, which represent the primary cellular target of morphine, is still undetermined. Recently, we investigated the role of these neurons in the habenula (HbMOR), an aversion center, in affective states. We used Oprm1-Cre knockin mice combined with optogenetics and behavioural testing to investigate the consequences of HbMOR stimulation on emotional responses. Our first findings showed that HbMOR neurons encode aversive states in a projection-specific manner (Bailly et al., 2023). We thus hypothesize that endogenous opioid release limits aversive states at the level of the habenula, and that adaptations following repeated opioid exposure lead to a hyperactivity following opioid withdrawal.

Methods: To test this hypothesis, using fiber photometry in Oprm1-Cre knockin mice, we first measured neuronal activity of HbMOR during blockade of endogenous and exogenous opioid tone by administration of naloxone, an opioid receptor antagonist. To then test causality between increased HbMOR activity and aversion, we chemogenetically inhibited HbMOR during conditioned place aversion to high-dose and low-dose naloxone in naïve and morphine-dependent states, respectively.

Results: We found increased activity of HbMOR neurons following high-dose (10mg/kg) naloxone administration in a naive state, and low-dose (0.1mg/kg) naloxone in an opioid-dependent state. Then, we found that HbMOR inhibition decreased avoidance of naloxone-paired compartments in both naïve and opioid-dependent mice.

Conclusions: These findings highlight the role of endogenous opioid activity in limiting aversion at the level of the habenula, and that alterations to this circuitry underlie negative affect during withdrawal from opioids.

Disclosure: Nothing to disclose.

35.4 Multilevel sex differences in medial habenula-interpeduncular nucleus circuit drive divergent alcohol consumption behaviors

Junshi Wang

Icahn School of Medicine At Mount Sinai, New York, New York, United States

Background: The prevalence of alcohol use disorder (AUD) is rising in women, who suffer severe health consequences from alcohol use. Thus, understanding the mechanisms driving alcohol intake in women is critical. The medial habenula (MHb), though small, regulates aversion, negative affect, and withdrawal-related behaviors. MHb neurons almost exclusively project to the interpeduncular nucleus (IPN). The IPN mediates avoidance behaviors, likely guided by aversive signals from the MHb. Manipulation of the IPN produces behavioral outcomes similar to MHb interventions, supporting that the MHb and IPN form a key circuit processing aversive information to influence behaviors. Thus, we aim to investigate the role of the MHb-IPN circuit in AUD comprehensively.

Methods: C57BL/6J and the α5 subunit of nicotinic acetylcholine receptor (nAChR) knockout mice (CHRNA5-KO) of both sexes were used. Single-cell RNA seq was performed using the 10x Genomics Chromium platform with ScanPy-based analysis. Whole-cell patch-clamp with optogenetics assessed neural activity and synaptic transmission. Alcohol intake was measured via operant ethanol self-administration. MAPseq (Multiplexed Analysis of Projections by Sequencing) profiled connectomes and connectivity strength at single-cell resolution.

Results: Ethanol enhanced MHb cholinergic neuron firing in both males and females (M: t10 = 3.6, p < 0.01; F: t8 = 13.5, p < 0.01). The resulting increase in MHb-derived acetylcholine (ACh) activated nAChRs in the IPN, leading to enhanced GABA release only in females (t35 = 4.0, p < 0.01). Consistently, alcohol only increases GABA release in the IPN of females (t23 = 3.3, p < 0.01), and this increase is abolished in Chrna5-KO female mice (t19 = 0.13, n.s). Pathway-specific electrophysiology further revealed a sex difference in IPN efferent connectivity strength (t38 = 3.5, p < 0.01), which was absent in Chrna5-KO mice (t46 = 1.1, n.s). Finally, targeted deletion of Chrna5 in the IPN using Crispr-Cas9 reduced ethanol intake selectively in females (t12 = 2.2, p < 0.05), with no effect observed in males (t14 = 0.2, n.s).

Conclusions: α5-containing nAChRs in the IPN mediate sex-specific differences in the MHb-IPN circuit at molecular, synaptic, and circuit levels, driving elevated alcohol intake in females.

Disclosure: Nothing to disclose.

Panel

36. Extracellular Vesicles as Potential Biomarkers in Psychiatry

36.1 miR-151a-5p cargo in neuron-derived extracellular vesicles mediates antidepressant treatment response

Gustavo Turecki

McGill University, Montreal, Canada

Background: Recent studies have shown that brain cells, including neurons, secrete extracellular vesicles (EVs) carrying specific molecular cargo capable of crossing the blood-brain barrier. These vesicles, detectable in peripheral blood, hold promise as non-invasive biomarkers that could reflect the brain’s molecular state and shed light on mechanisms underlying antidepressant response.

Methods: We examined 430 plasma samples from the CAN-BIND-1 clinical trial (clinicaltrials.gov, NCT01655706). Samples were collected before and after an 8-week course of escitalopram treatment in patients with depression alongside untreated controls. Neuron-derived extracellular vesicles (NEVs) were isolated using size exclusion chromatography followed by immunoprecipitation targeting SNAP25, a neuron-specific membrane protein found on the surface of NEVs. NEV miRNA content was profiled using small RNA sequencing and validated via RT-qPCR.

Results: At baseline, depressed patients exhibited lower NEV miR-151a-5p levels than controls (p < 0.01, n = 71–73). Post hoc analysis for Time 0: Control vs Responder (R) (p < 0.01), Control vs Non-R (p < 0.01) and R vs Non-R (p = 0.114). Notably, only patients who responded to treatment showed a significant post-treatment increase. miR-151a-5p levels in NEVs effectively distinguished Rs from non-Rs (Time 8: Control vs Rs p = 0.086, Control vs Non-Rs p < 0.05, Rs vs Non-Rs, p < 0.05).

Further investigation showed a similar decrease in miR-151a-5p levels in NEVs isolated directly from the prefrontal cortex of individuals who had depression and died either naturally (MDD) or by suicide (p < 0.01; Control vs MDD p < 0.05, Control vs Suicide p < 0.05, MDD vs Suicide p = 0.99, n = 10).

In vitro and computational analyses showed that miR-151a-5p downregulates genes enriched in the prefrontal cortex involved in biological processes regulating synaptic organization and function. Engineered NEVs loaded with miR-151a-5p and administered to the prefrontal cortex of mice subjected to social defeat test produced antidepressant-like effects and reversed stress-induced behavioral changes in mice (p < 0.05, n = 8–15).

Conclusions: These findings suggest that NEVs collected from the peripheral samples reflect molecular changes occurring in the brain, and that miR-151a-5p in NEVs mediate antidepressant response.

Disclosure: Nothing to disclose.

36.2 Astrocyte-enriched extracellular vesicle microRNAs reveal inflammation-related biological processes

Leandra Figueroa-Hall

Laureate Institute for Brain Research, Tulsa, Oklahoma, United States

Background: Inflammation-associated depression is characterized by elevation of serum inflammatory molecules in about 30% of depressed individuals. However, the pattern of immune activation in the brain remains unclear. Examination of brain-enriched extracellular vesicle (EV) cargo may provide a window into brain-specific mechanisms. Here, we investigate astrocyte-enriched EV (AEEV) miRNA differential expression (DE) and gene target prediction in the context of an inflammatory challenge.

Methods: This preliminary work leveraged a randomized clinical trial (NCT03142919) involving acute administration of low-dose lipopolysaccharide (LPS; 0.8 ng/kg) or placebo (saline) to individuals with major depressive disorder (MDD) and healthy controls (HC). Serum was used to isolate total EV, and an astrocyte-specific glutamate transporter (GLAST) antibody used for AEEV enrichment. AEEV miRNAs were sequenced with Next Generation Sequencing and analyzed for DE, gene target prediction and Gene Ontology (GO) enrichment, 1.5 (T1.5) hours after LPS administration. To reduce noise from low expression miRNAs, cutoffs were established for each cohort that resulted in 14 MDD participants [LPS (n = 10); placebo (n = 4)]. Normalization was performed in R via the DESeq2 package (version 1.46.0) using the “median of ratios” method. For DE analysis, unadjusted p-values were used for initial indication of potential associations.

Results: There were 93 differentially expressed miRNAs (|log2FC|> 1.5 and padj < 1) in the LPS vs placebo group. The following AEEV miRNAs were downregulated: hsa-miR-510-5p (p < 0.01; log2FC = −6.28); hsa-miR-3168 (p < 0.05; log2FC = −2.77); hsa-miR-192-5p (p < 0.05; log2FC = −3.98); and hsa-miR-1243 (p < 0.05; log2FC = −7.01). These miRNAs were predicted to interact with genes involved in the inflammatory response such as interleukin-10, IRAK1, and TLR4. GO-term enrichment identified biological processes such as gliogenesis (p = 3.75E-13) and regulation of canonical NF-kappaB signal transduction (p = 6.05E-08).

Conclusions: These findings demonstrate that in response to experimentally induced inflammation, astrocytes release extracellular vesicles with a distinct miRNA signature, pointing to a novel mechanism by which these brain cells regulate inflammatory processes, such as NF-kappaB signaling, implicated in depression.

Disclosure: Nothing to disclose.

36.3 Adolescence as a sensitive period for exposure to interpersonal violence: physiological and proteomic biomarkers of risk

Tanja Jovanovic

Wayne State University School of Medicine, DETROIT, Michigan, United States

Background: Interpersonal violence (IPV), is associated with increased risk for neuropsychiatric disease, including posttraumatic stress disorder (PTSD). Late adolescence is a sensitive period for emergence of internalizing psychopathology, as well as when prefrontal cortex development may be most vulnerable to trauma. The current study examined fear-potentiated startle (FPS) and extracellular vesicles (EVs) in adult men and women who experienced IPV only during one of two developmental windows: prior to age 14 or between 14 and 18 years of age, but not both. A control group without IPV exposure was also included. We hypothesized that these biomarkers would be increased specifically in women who experienced IPV during adolescence.

Methods: Participants included N = 98 adults (60 women) from the Detroit Trauma Project who had IPV exposure exclusively during the selected developmental windows. FPS was measured using EMG during fear conditioning. Von Frey testing was conducted using standardized methods for humans with ascending and descending fibers. Proteins were analyzed from plasma on a coupled Thermo Scientific Orbitrap Fusion Lumos Tribrid mass spectrometer.

Results: We found both sex-specific and IPV-group patterns in physiological and EV biomarkers. FPS to the CS+ during the last block of acquisition was highest in the adolescent IPV group (p = 0.05), which was driven largely by females. We also found that sensory thresholds increased linearly across von Frey trials in those with IPV exposure (p = 0.017), which was also strongest in females with adolescent exposure. When protein abundance was compared between IPV age groups, here was a distinct profile of differentially abundant proteins based on the age of exposure. Keratin-associated proteins were uniquely and widely increased in women who had experienced sexual trauma at age 14–18 (p’s ranged from 4.4e-4 to 1.54e-21).

Conclusions: We found that IPV in late adolescence increased threat responses, showed habituation to sensory thresholds, and more keratin-related proteins in their EVs decades later. These results underscore the critical importance for understanding the developmental timing of when trauma occurred as a predictor for the lasting influence mental health outcomes. Identification of unique biomarkers in individuals with adolescent IPV may provide novel insight into interventions.

Disclosure: Nothing to disclose.

36.4 EVs as biomarkers in psychiatry: building a computational normative framework around stress

Tracy Bale

University of Colorado, School of Medicine, Aurora, Colorado, United States

Background: Psychiatry currently lacks reliable validated blood biomarkers. Extracellular vesicles (EVs) are cell-derived nanoparticles that play a crucial role in cell-to-cell communication to maintain homeostasis and have emerged as promising biomarkers across health and disease states. The goal of this study was to build a computational ‘normative’ framework in humans on which all future disease-based EV studies can be applied to distinguish between healthy EV responses and those that may be predictive or causal in disease states.

Methods: We examined changes in plasma and salivary EVs and their association with physiological stress markers in male and female healthy adults. Twenty-seven healthy participants (14 males, 13 females; aged 21–35 years) completed a single visit consisting of three 20-minute experimental phases: T1 (baseline; relaxation video), T2 (stress exposure; stress video), and T3 (recovery; quiet reading). Heart rate and skin conductance were continuously monitored, while blood and saliva samples and subjective ratings of perceived stress were collected after each phase. EVs were isolated using Izon size exclusion chromatography, and their concentration and size were analyzed via nanoparticle tracking analysis using the ZetaView.

Results: Male and female participants reported significantly increased perceived stress (T2; p < 0.001). Skin conductance increased at T2 in both males (p = 0.024) and females (p = 0.047). In males, plasma cortisol was significantly changed (p = 0.001). In contrast, females had overall lower cortisol and no change with stress. Only males showed an increase in EV concentration at T2 (p = 0.019). Interestingly, female salivary EVs increased in size with stress at T2 (p = 0.044). EV proteomics data will be computationally modeled to identify protein pathways and functions between stress phases and by sex utilizing computational modeling and multi-modal data (HR, SC, and cortisol).

Conclusions: This study is the framework for building a computational model that will provide insight into EVs as biomarkers predictive of stress as potential predictors and diagnostics in neuropsychiatric disorders. Stress-elicited changes in EV characteristics, with distinct sex-dependent patterns, as well as current EV proteomics modeling underway, demonstrate immense predictive power using within subject studies.

Disclosure: ProNovo Therapeutics, Founder, Spouse/Partner

Panel

37. Brain Health and Mental Health in Women Across Reproductive Transitions and the Lifespan: Evidence From Multi-Modal Brain Imaging Studies

37.1 Hippocampal neurodevelopment and menarche impacts cognitive and clinical symptoms

Katherine Damme

University of Texas at Dallas, Dallas, Texas, United States

Background: Estrogens have been linked to lasting and acute effects on the hippocampus and related cognition. Psychosis risk has been related to increased hippocampal vulnerability to stress, causing dysconnectivity and dysfunction that drive symptom progression and onset. New evidence suggests that menarche timing moderates hippocampal dysconnectivity at rest for those at risk for psychosis but has not examined the role of cognition in this mechanistic pathway. Normative effects of estrogen may account for sex differences in psychosis onset and cognitive function.

Methods: The Adolescent Brain Cognitive Developmental (ABCD) Study includes over 4000 individuals with at least three time points that include pre/post-menarche data across imaging, cognitive, and clinical (psychotic-like experience (PLE) severity). I expect that working memory (Emotional N-Back: 2-0-back; NIH cognitive toolbox list task) would benefit from the availability of estrogens after menarche, which may be moderated by changes in hippocampal activation or connectivity. I expect that these benefits vary by psychosis burden/hippocampal vulnerability.

Results: Post-menarche status was associated with higher working memory accuracy (N-back p < .001; lists p = 0.03), but not other subscales (p’s > 0.35), and predicted increased hippocampal-frontal connectivity during the N-back task (p < 0.001). Working memory accuracy related to hippocampal activation (p = 0.045) and menarche (p < 0.001). Menarche’s impact on working memory performance varied along a psychosis risk burden spectrum (p < 0.001). Those with the highest PLE severity showed greater improvement in working memory performance (d = 1.21) compared to those with lower PLEs (d = 0.95).

Conclusions: Estrogen availability (post-menarche) was related to better working memory performance as a part of normative development. This normative benefit was specific to working memory and not a general cognitive benefit. This benefit was particularly large in individuals with a high psychosis risk burden, which may reflect the those with hippocampal vulnerability. These findings provide an important initial framework for conceptualizing how the brain and cognition may play an important role in sex differences in the delay of initial psychosis onset and higher function throughout psychosis clinical course.

Disclosure: Nothing to disclose.

37.2 Precision imaging of the human brain across pregnancy and postpartum

Emily Jacobs

University of California, Santa Barbara, Santa Barbara, California, United States

Background: Worldwide, nearly 85% of women will experience pregnancy in their lifetime. Over the ~40-week gestational window the maternal body undergoes profound, coordinated physiological adaptations to support the developing fetus, including major shifts in immune regulation at the feto-maternal interface and dramatic changes in the vascular system. Accompanying these peripheral adaptations, rodent studies have established pregnancy as a period of widespread neuroplasticity that facilitates the onset of maternal behaviors. Despite decades of impactful work in animal models, scientists are just beginning to understand how the human brain adapts to this major life transition. Fundamental questions about the maternal brain remain unanswered. To address this gap, this project maps the structural and functional changes that unfold in the maternal brain throughout pregnancy and the postpartum period.

Methods: Primiparous women (n = 8, ages 25–40; yielding > 200 MRI datasets) are enrolled at UC Santa Barbara and UC Irvine School of Medicine for up to 30 sessions consisting of multimodal imaging, blood sampling, and neuropsychological assessment conducted from preconception through one year postpartum. Age-matched nulliparous controls provide a benchmark of typical physiological changes over time.

Results: Cortical volume decreases throughout pregnancy, dips near parturition, and partially recovers in the postpartum. Reciprocally, cerebrospinal fluid volume shows increases during gestation, peaks at parturition, and returns to preconception levels during postpartum. Global anisotropy of white matter increases throughout the first and second trimesters and then returns to baseline levels in the postpartum period. Finally, cerebral blood flow increases up to the second trimester and then returns to baseline levels at term. These changes are highly choreographed across healthy pregnancies. Pre-eclamptic pregnancy shows a divergent profile, with blunted perfusion changes across the gestational window.

Conclusions: In a first of its kind precision imaging dataset of the maternal brain, we observe sweeping changes in gray matter volume and white matter microstructure week by week, offering neuroscientists a detailed map of the human brain across gestation.

Disclosure: Nothing to disclose.

37.3 Association of vasomotor symptoms with resting stress and acute stress responsivity in midlife women: neural activation and the GABAergic system

Pamela Mahon

Mass General Brigham, Harvard Medical School, Boston, Massachusetts, United States

Background: Neurally-derived symptoms are a primary manifestation of the menopause transition, with vasomotor instability as the core feature of reproductive aging. Vasomotor symptoms (VMS) affect up to 85% of women in menopause, last for 7.4–9.0 years on average, and are closely linked with worse neuropsychological health outcomes—cognitive function, daytime functioning, depressive and anxiety symptoms, and stress perception. The hypothalamic neuropeptide neurokinin B induces VMS, which are modulated by stress. We propose a novel conceptualization of VMS as a chronic stress condition with dysregulated neural stress responsivity, reflecting processes through which stress mediates the adverse brain health outcomes of VMS.

Methods: 57 peri- and post-menopausal women with and without VMS completed multimodal imaging with task-related functional MRI across a psychosocial stress task with no stress, moderate stress, and high stress conditions at 3 Tesla, as well as GABA levels in a ventromedial prefrontal cortex (VMPFC) voxel measured from magnetic resonance spectroscopy (MRS) at 7 Tesla. VMS group differences (VMS+; N = 47 vs VMS-; N = 10) in fMRI activation and GABA were tested using general linear models, adjusting for age. Post hoc secondary analyses examined partial correlations of fMRI activation and GABA with VMS symptom duration.

Results: In response to moderate stress (vs. no stress), the VMS+ group had lower activation (vs VMS-) in the hippocampus [F(1,47) = 4.6, p = 0.037] and insula [F(1,47) = 5.1, p = 0.029]. Additionally, in response to maximal stress (vs. no stress), VMS+ exhibited lower activation in the orbitofrontal cortex [F(1,47) = 4.1, p = 0.048]. Among VMS + , longer duration of VMS symptoms was inversely associated with activation in the insula in response to moderate stress (vs. no stress) [r = −0.35, p = 0.028]. Longer duration of VMS was also positively associated with GABA in the VMPFC at the trend level [r = 0.33, p = 0.073].

Conclusions: Our findings demonstrate that women with VMS have altered neural activation in response to stress, consistent with what is seen in stress-related disorders. Duration of VMS is associated with altered neural activation in response to stress as well as a marker of brain GABAergic functioning at a trend level. Taken together, these results suggest that neurokinin-induced VMS represent a chronic stress condition.

Disclosure: Nothing to disclose.

37.4 Sex, age-at-menopause and hormone therapy use predict increasing levels of pTau217 in preclinical Alzheimer’s disease: findings from the Wisconsin Registry for Alzheimer Prevention

Gillian Coughlan

Massachusetts General Hospital, Boston, Massachusetts, United States

Background: Neuroimaging studies using positron emission tomography (PET) show that older women exhibit accelerated rates of tau tangle accumulation relative to age-matched men, particularly in the context of preclinical Alzheimer’s disease (i.e. high amyloid-beta [Aβ] in the absence of clinical symptoms). The extent to which sex predicts the the secretion of upstream soluble phosphorylated tau (p-Tau) remains unclear. To address this, we assessed pTau217 trajectories as a function of sex in a relatively younger preclinical AD cohort and further investigated whether female-specific factors, including age-at-menopause and timing of HT initiation, were also associated with pTau217 accumulation over time.

Methods: Data were collected from 329 cognitively unimpaired men and women from the Wisconsin Registry for Alzheimer’s Disease (mean age 61.89 (SD = 7.01; 218 women[66%]; 123 APOEε4 carriers[37%]; Table) who had longitudinal pTau217 acquired with the ALZPath immunoassay over 4.71 years on average (SD = 1.92) and underwent dynamic Pittsburgh Compound-B[PiB] PET for a measure of global Aβ burden. 128[43.6%] women reported use of HT(past/current).

Results: In the context of high Aβ-baseline, being female (βstandardized = −0.16; 95%CI: − 0.22 to −0.10; P < 0.001) was associated with increasing pTau217 relative to men. In women, earlier age at menopause (β = −0.05; 95%CI: − 0.08 to − 0.03; P < 0.001), and HT-use (β = −0.11; 95%CI: 0.04 to 0.19; P = 0.002) were associated with increasing pTau217 levels among individuals with elevated Aβ compared with later age at menopause, and HT nonuse. Late initiation of HT (>5 years following age-at-menopause) was weakly associated with increasing ptau217 levels compared with early initiation (β = 0.08; 95%CI: 0.02 to 0.10; P = 0.016), particularly in the setting of high Aβ-baseline (β = 0.07; 95%CI, 0.02 to 0.11; P = 0.002).

Conclusions: These findings suggest that sex differences occur proximal to the secretion of Aβ-related soluble pTau217. Among women with elevated Aβ, menopause factors may heighten vulnerability to both soluble and insoluble tau accumulation, informing sex-specific Alzheimer’s risk.

Disclosure: Nothing to disclose.

Panel

38. Top-Down Control of Defensive State Selection in the Face of Threats

38.1 Neuronal circuits of innate threat processing and adaptive learning

Susanna Molas

The University of Colorado Boulder, Boulder, Colorado, United States

Background: Defensive behaviors and adaptive threat learning are essential for survival. The tail of the striatum (TS), the most caudal region of the striatum, integrates sensory and cognitive inputs from cortical, thalamic, and monoaminergic areas. Emerging evidence implicates the TS in processing novel, threatening, and salient stimuli. However, the specific TS neuronal circuits engaged during initial threat exposure and how they adjust with threat learning remain poorly understood.

Methods: We employed fiber photometry with the dLight biosensor to measure dopamine (DA) dynamics in the TS of C57BL/6J mice (n = 6 males) in response to a visual looming stimulus (VLS) threat, as well as across repeated exposures over multiple days. For comparison, DA signals were also monitored in the nucleus accumbens (NAc) (n = 7 males). To assess postsynaptic dopaminergic signaling, we recorded activity of spiny projection neurons (SPNs) in DA receptor 1 (D1R)-Cre mice (n = 5 males, 5 females). Additionally, we used the Targeted Recombination in Active Populations (TRAP2) system to label TS neurons activated during initial VLS exposure and subsequent VLS learning (n = 3–6 mice per group, both sexes).

Results: We observed robust DA signaling in the TS during initial VLS exposures, which significantly declined across days (One-way ANOVA; day effect: F(1.845, 9.227) = 18.38, p = 0.0007). In contrast, VLS did not elicit detectable DA responses in the NAc, suggesting regional specificity in dopaminergic threat processing. Recordings from TS D1-SPNs revealed strong activation during early VLS exposures, followed by a marked decrease with repeated presentations (Two-way ANOVA; day effect: F(1.367, 10.93) = 7.641, p = 0.0133; sex effect: F(1, 8) = 0.4711, p = 0.5119). Finally, using the TRAP2 system, we labeled TS neuronal ensembles activated during initial VLS exposure, which were no longer detectable following repeated presentations, indicating their transient engagement during early threat processing.

Conclusions: These findings identify DA signaling and postsynaptic networks within the TS as a critical hub for encoding threat responses and enabling flexible behavioral adaptations to environmental threats. Importantly, this work has broad implications for understanding maladaptive threat processing underlying psychiatric conditions such as anxiety disorders.

Disclosure: Nothing to disclose.

38.2 Internal state-dependent gating of peripheral threat detection by area prostriata

Mario Penzo

National Institute of Mental Health, Bethesda, Maryland, United States

Background: Internal states, such as hunger, reconfigure sensory and attentional systems to optimize behavioral priorities under changing physiological demands. While this adaptation supports survival by promoting foraging, it may compromise vigilance and the ability to detect threats, particularly those emerging unexpectedly from the visual periphery. The cortical region known as area prostriata (APr) has been implicated in peripheral motion processing in primates and humans, but its function in behavior remains unexplored. Here, we provide the first functional characterization of rodent APr, revealing it as a metabolically sensitive visual area that gates escape responses to looming threats.

Methods: We combined single-cell calcium imaging, chemogenetics, and looming-evoked behavior in male and female mice. Visual stimuli varied in eccentricity (–30° to 120°) and expansion speed (3–300°/s). Internal state was manipulated via food deprivation (12–24h) or ghrelin injection (0.5–1.0 mg/kg). Escape latency to shelter was measured in freely moving animals. Head-fixed calcium imaging with GCaMP6s recorded responses in > 100 APr neurons per condition. APradcyap1 neurons were targeted with hM3Dq or hM4Di DREADDs. Patch-clamp recordings assessed excitability changes.

Results: Escape latency increased with 24h food deprivation (β = 0.86 ± 0.13, p < 0.0001) and ghrelin (1.0 mg/kg: β = 0.74 ± 0.16, p < 0.0001). Chemogenetic inhibition of APradcyap1 neurons mimicked this effect in sated mice (β = 0.44 ± 0.18, p = 0.016), while activation rescued hunger-induced impairments (β = –0.82 ± 0.21, p = 0.0002). APr neurons (n > 900 across groups) were tuned to rapid peripheral stimuli (β = 0.33 ± 0.07, p < 0.0001); this tuning was abolished by hunger (β = –0.03 ± 0.06, p = 0.66). Recordings were collected from 8–10 mice per condition. Food deprivation reduced intrinsic excitability of APr-adcyap1 neurons.

Conclusions: APr integrates internal physiological signals with visual input to guide adaptive defensive behavior. These findings identify a novel state-sensitive visual cortical circuit and suggest a mechanism by which interoceptive dysfunction may contribute to abnormal threat processing in anxiety disorders. Ongoing studies are defining thalamocortical pathways that relay metabolic signals to APr, enabling state-dependent modulation of visual processing.

Disclosure: Nothing to disclose.

38.3 Differential roles of dopamine D1- and D2-receptor neurons in the prelimbic cortex during approach-avoidance conflict in rats

Fabricio Do Monte

The University of Texas Health Science Center at Houston, Houston, Texas, United States

Background: The prelimbic (PL) subregion of the medial prefrontal cortex is essential for decision-making processes, including approach-avoidance conflict situations where reward and threat cues co-occur. Dopamine modulates PL activity via excitatory type-1 (D1R) and inhibitory type-2 (D2R) receptors, which have minimal overlapping expression in PL neurons. However, the precise involvement of D1R or D2R neurons, alongside dopamine dynamics in PL, during approach-avoidance conflict remains unknown.

Methods: Both male and female wild-type, D1R-Cre and D2R-Cre adult Long-Evans hooded rats (n = 11–14 per group), previously trained to press a lever for sucrose during audiovisual cues, were exposed to the food-associated cues in the presence of a neutral odor (reward phase), a fear-inducing cat odor (conflict phase), and the cat odor-associated context (contextual conflict phase). Fiber photometry was used to measure dopamine levels (GRAB-DA sensor) and the activity of D1R and D2R neurons (GCaMP7f) in PL. Optogenetics was employed to activate (ChR2) or silence (eNpHR) D1R and D2R neurons in PL during the food cues (n = 7–12 per group).

Results: Rats showed increased defensive behaviors and reduced food seeking during conflict and contextual conflict phases. During the reward phase, dopamine levels and D1R neuron activity increased at food cue onset (Z-score > 2.58, p < 0.01), while D2R activity decreased (Z-score < −1.96, p < 0.05). Interestingly, these changes were attenuated during the conflict phase. During the contextual conflict phase, risk-taking trials were associated with higher dopamine levels (p = 0.0007), increased D1R (p = 0.028), and decreased D2R (p = 0.0056) neuronal activity during food cues, compared to risk-avoidance trials. Photoactivating PL-D1R neurons or silencing PL-D2R neurons during the food cues of the contextual conflict phase biased rats’ behavior toward food-seeking responses, as shown by increased lever presses during the cues (D1-control: 1.3 ± 0.7, D1-ChR2: 8.1 ± 2.7, p = 0.024; D2-control: 2.0 ± 1.4, D2-eNpHR: 7.1 ± 1.8, p = 0.042).

Conclusions: Our findings reveal that elevated dopamine levels in PL during food cue presentation are associated with increased risk-taking behavior, and that modulation of PL-D1R and PL-D2R neural activity produces opposing behavioral effects during approach-avoidance conflict.

Disclosure: Nothing to disclose.

38.4 Somatostatin neuropeptidergic transmission shapes emergent properties of prefrontal cortical circuits underlying learning

Hugo Tejeda

National Institute of Mental Health, Bethesda, Maryland, United States

Background: The prefrontal cortex (PFC) contains distinct inhibitory sub-populations, including somatostatin-positive interneurons. SST, a neuropeptide transmitter that signal via G-protein coupled SST receptors (SSTRs), has been widely used as a cellular marker of SST-positive interneurons. However, a critical knowledge gap remains in understanding the physiological role of the SST “cellular marker” in regulating top-down control of defensive behavior and emergent properties of PFC circuit dynamics in-vivo.

Methods: We used a viral/genetic to selectively knock out SST expression in the medial PFC (mPFC) in male and female SST loxP mice and examined its impact on cued threat discrimination (n = 15–17). SST interneuron activity and neuropeptidergic dynamics were examined during cued-threat discrimination using single cell Ca2+ imaging (n = 9) and fiber photometry recordings of a genetically-encoded SST sensor (GRAB-SST; n = 8), respectively. We examined the impact of SST transmission on mPFC pan-neuronal single cell Ca2+ dynamics during cued-threat discrimination (n = 4–6) in control and SST-loxP mice. Statistical analyses included ANOVA, Fisher’s Exact test, or t-tests.

Results: Controls exhibited robust freezing to the footshock paired cue (CS+) but not a neutral cue (CS-), while mPFC SST knockouts froze to both (p = 0.0006). GRAB-SST responses during threat acquisition were evoked by footshock delivery and the CS+, but not to the neutral cue (p = 0.0049). Intra-mPFC SSTR antagonism during threat discrimination acquisition, but not expression, impaired expression of cued-threat discrimination (p = 0.0046). mPFC SST neuropeptidergic transmission was necessary for neurons to multiplex salient footshock outcomes with other variables to form configural representations (p = 0.0005) and facilitates population-level encoding associated with discriminative learning (p = 0.0425).

Conclusions: Collectively, this study provides evidence of endogenous mPFC SST signaling in shaping learning and emergent properties of mPFC circuits, highlighting the importance of a neuropeptidergic signal classically used as a marker of inhibitory interneurons. This is of relevance since decreased PFC SST expression and immunoreactivity has been implicated in numerous psychiatric disorders, including depression, bipolar disorder, and schizophrenia.

Disclosure: Nothing to disclose.

Panel

39. Latest Advances in Neuroimaging of PTSD: From Fear Learning and Extinction Pathways to Decoding Naturalistic Trauma Memory

39.1 PTSD is characterized by extreme neural deviations during fear conditioning

Miguel Fullana

IDIBAPS/Hospital Clínic Barcelona, Barcelona, Spain

Background: There is ongoing debate about whether fear-related disorders consistently exhibit abnormalities in fear conditioning—at behavioral or neural levels—or whether such abnormalities are specific to certain clinical groups, such as post-traumatic stress disorder (PTSD), but not others, like social anxiety disorder (SAD) or generalized anxiety disorder (GAD).

Methods: Leveraging data from the ENIGMA-FearConditioning consortium (N = 1800 controls; N = 222 individuals with fear-related disorders), we generated normative models of brain activation during fear conditioning. These models were applied to an independent clinical test sample (N = 260 controls; N = 222 with fear-related disorders) to derive normative probability maps. For each participant, we quantified the number of significantly deviating voxels and compared groups using the Kruskal-Wallis H-test, followed by Mann-Whitney U-tests with False Discovery Rate (FDR) correction (α = 0.05). Additionally, we trained a one-vs-rest support vector classifier (SVC OvR) using whole-brain unthresholded deviation maps to identify diagnostic group–specific patterns (PTSD: N = 55; obsessive-compulsive disorder [OCD]: N = 68; GAD: N = 48; SAD: N = 31).

Results: Extreme neural deviations were most frequent in individuals with PTSD relative to other fear-related disorders (p < .005). PTSD was characterized by large positive deviations in the bilateral medial occipital cortex (extending to the inferior temporal lobe and lingual gyrus), bilateral ventrolateral prefrontal cortex (vlPFC), dorsomedial prefrontal cortex (dmPFC), precuneus, and bilateral amygdala. Large negative deviations were observed in the ventromedial prefrontal cortex (vmPFC), precuneus, and regions of the lingual and fusiform gyri. Individuals with PTSD exhibited a distinct pattern of deviations and were correctly classified 54.55% of the time by the multi-class SVC, suggesting a quantifiably differentiable neural phenotype.

Conclusions: Our findings suggest that PTSD is uniquely associated with marked disruptions in fear and threat-related neural processing, as revealed by normative modeling of fear conditioning tasks. In contrast, other fear-related disorders—particularly GAD and SAD—show fewer or less distinct deviations from normative patterns.

Disclosure: Nothing to disclose.

39.2 Contrasting patterns of neural activity, physiology, and autonomic synchrony during vicarious threat extinction in trauma-exposed adolescents with and without posttraumatic stress symptoms

Ryan Herringa

University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States

Background: The use of social cues to attenuate learned fear associations is a critical skill for normative development. Impairments in extinction learning underlie models of PTSD in adults. However, little is known about how trauma and related psychopathology may impact the neural and physiological processes of observed-parent vicarious safety learning during adolescence.

Methods: This study enrolled typically developing (TD, N = 42) and trauma-exposed (TE, N = 45) parent-child dyads, with youth further classified as having low (TE-Low) or high (TE-High) posttraumatic stress symptoms (PTSS). Dyads underwent a 3-day neuroimaging paradigm characterizing the transmission of parental social cues that may modify established threat associations. Each youth and caregiver completed acquisition (Day 1), direct (CS+Direct) and vicarious extinction (youth only) by watching a video of parent direct (CS+Vicarious; Day 2), and extinction recall (Day 3). Analysis of behavior, parent-child autonomic synchrony, and whole-brain voxelwise activation were used to characterize trauma- and PTSS-related correlates of vicarious extinction.

Results: Distinctive patterns of trauma and symptomatology emerged across behavioral, physiological, and neural correlates during vicarious extinction learning. Group x Phase interactions were driven in-part by higher shock expectancy in TE-High youth vs TD and TE-Low youth (F = 2.89, P = 0.003) during vicarious extinction. Parent-child autonomic synchrony, measured by skin conductance, was inversely correlated with PTSS in TR-Low (r = −0.61, P = 0.001) but attenuated in TR-High youth (r = −0.44, P = 0.079). Finally, activation in ventrolateral (K = 98, F = 13.76, PCORR < 0.05) and dorsolateral (K = 101, F = 9.67, PCORR < 0.05) prefrontal cortex show significant interactive effects of Group x Stimulus type x Trial, where TD youth exhibit decreasing recruitment from early to late vicarious extinction while TR-Low and TR-High youth show lower and increasing recruitment across phase in a dose-response fashion.

Conclusions: As compared to normative and trauma-exposed youth with low symptom burden, trauma exposed youth with high PTSS show distinct behavioral impairments in vicarious learning that may be related to disruptions in parent-child synchrony and altered recruitment of the lateral PFC during vicarious extinction learning.

Disclosure: Nothing to disclose.

39.3 Decoding the trauma memory: overlap with threat representations and change over time

Joshua Cisler

University of Texas at Austin, AUSTIN, Texas, United States

Background: Understanding the basic neurocircuitry mechanisms engaged when individuals with PTSD recall traumatic memories, and how these mechanisms change over time, has implications for understanding the basic mechanisms underlying exposure-based treatment approaches, where individuals are asked to repeatedly recall traumatic memories across multiple sessions. This study tested three distinct hypotheses: 1) that traumatic memory recall engage neurocircuitry representations that overlap with patterns engaged during general threat responding, 2) that neurocircuitry representations of threat engaged during trauma recall decrease across multiple sessions of trauma recall, 3) that increased dopamine signaling (via L-DOPA) in the consolidation window following repeated trauma memory recall potentiates reorganization of neurocircuitry representations after multiple sessions of trauma recall.

Methods: 79 women with PTSD participated. Participants created narratives of their index trauma and a neutral memory. Participants listened to and viewed each memory narrative 4 consecutive times during fMRI. Following the first MRI session, participants ingested either placebo (n = 37) or 100mg L-DOPA (n = 41). Participants returned for an identical imaging session 24hrs later.

Results: 1) A shock decoder, trained in an independent cohort undergoing threat learning (N = 125), made higher shock predictions when applied to trauma, compared to neutral, memory recall, in mid-cingulate and medial PFC networks.

2) Shock decoder output significantly decreased at trauma recall in session 2 in the medial PFC network but not mid-cingulate network. Similarly, a decoder trained to predict self-reported anxiety during memory recall demonstrated reduced anxiety predictions at session 2 in the mPFC but not mid-cingulate network.

3) Those receiving L-DOPA after session 1 had reduced anxiety decoder output in the mPFC at session 2.

Conclusions: These data suggest shared neurocircuitry between general aversive stimuli (shocks) and trauma recall. Multiple sessions of exposure to the trauma memory decreased shock and anxiety brain representations in the mPFC but not mid-cingulate. Increased dopamine signaling following an initial trauma memory recall potentiates reduced anxiety representations in the mPFC during trauma memory recall.

Disclosure: Nothing to disclose.

39.4 Neural signature of real-life trauma memories

Abstract Not Included

Panel

40. Beyond Craving: Application of Repetitive Transcranial Magnetic Stimulation Targeting Alternative Cognitive Functions is Safe and Effective in Substance Using Samples

40.1 Insula networks related to distress tolerance among tobacco use disorder

Merideth Addicott

Wake Forest University, School of Medicine, Winston-Salem, North Carolina, United States

Background: A key motivator of tobacco use is the escape or avoidance of affective distress. Distress tolerance (DT), the ability to persist in a goal-directed activity while experiencing affective discomfort, increases the likelihood of quitting tobacco. Using rTMS to modulate functionally connected insula networks that underlie affective DT could support cessation outcomes by regulating stress-induced craving. Our previous work found that during a DT paradigm, task-based functional connectivity (TBFC) with the insula differentiated iTUD who quit (>2 years ago) from those who had not, and rTMS modulated this TBFC with the insula among healthy controls. The goal of this study is to associate DT TBFC with cessation outcomes during a quit attempt, which will help inform future rTMS targets for iTUD.

Methods: Our DT paradigm, the PASAT-M, creates a conflict between attending to a math task versus being distracted by aversive auditory feedback. Importantly, the PASAT-M reveals unique differences in TBFC with anterior insula (AI) and posterior insula (PI) networks, which are integral to interoceptive awareness and its subjective emotional interpretation, respectively. Here, iTUD (n = 48) underwent fMRI while performing the PASAT-M. Then, they set a quit date and kept a smoking diary. The quit attempt was supported by nicotine replacement therapy and smoking was tracked for 10 weeks.

Results: As of March 2025, 17 participants quit tobacco for at least 1 day (Quit Attempt) while 31 participants did not (No Quit). Similar to our previous research, in the PASAT-M Distress Condition the Quit Attempt group had stronger negative TBFC than the No Quit group in the left PI and the bilateral putamen (p < .05). Furthermore, Quitters who were abstinent the longest had the strongest negative TBFC difference values (Distress – Control Condition) in the left PI cluster (r = −.44, p = .002). Among all participants, accuracy decreased as negative mood and craving increased (r = −.34, p = .019). No self-reported differences between groups were significant.

Conclusions: The PASAT-M elicits reproducible TBFC in the PI and AI. Here, we report a TBFC pattern unique to short-term cessation success. Altogether, this line of research suggests affective distress and its underlying insula-based TBFC is a feasible target for neuromodulation to support smoking cessation.

Disclosure: Nothing to disclose.

40.2 Restoring prefrontal cognitive control in methamphetamine use disorder: a randomized repetitive transcranial magnetic stimulation with source-localized electroencephalogram (EEG)

Di Zhao

Shanghai Jiao Tong University School of Medicine, Shanghai, China

Background: Methamphetamine use disorder (MUD) is marked by core deficits in cognitive control, particularly impaired inhibition and attentional bias, which directly linked to clinical symptoms like craving and impulsivity. While high-frequency rTMS over the left DLPFC has shown clinical promise, its capacity to restore cognitive control and the underlying cortical mechanisms, especially in comparison to alternative protocols, remains unknown. HD-EEG with source localization offers a powerful tool to elucidate these cognitive-neural links for targeted intervention.

Methods: This double-blind RCT enrolled 106 male inpatients with moderate-to-severe MUD, confirmed by DSM-5 and urine screening, excluding comorbid substance or major psychiatric disorders. Participants received 20 sessions of either HF (10 Hz) rTMS over left DLPFC, sequential LF (1 Hz) right then HF left DLPFC, or HF (10 Hz) vertex (control). Primary outcomes were inhibitory control, and drug-cue attentional bias; secondary outcomes included craving and impulsivity. HD-EEG measured pre- and post-treatment oscillatory changes with source localization. Groups were balanced demographically. The trial was registered and ethically approved.

Results: Stop-signal task performance showed a significant time × group interaction (F = 7.04, p = 0.012, η² = 0.176), as did drug-cue attentional bias (F = 11.10, p = 0.004, η² = 0.382). Post hoc FDR-corrected tests showed the HF left DLPFC group improved inhibitory control and reduced attentional bias versus vertex controls (both p values < 0.05), with decreased craving and impulsivity. Treatment was well tolerated; mild headache occurred in 8.3% (HF left), 13.8% (bilateral), and 2.7% (vertex). Bilateral stimulation caused more early discomfort but no serious adverse events. HD-EEG revealed increased theta and beta power in left DLPFC and anterior cingulate predicted inhibitory control gains (r = 0.51, p < 0.001), suggesting neurophysiological recovery mechanisms.

Conclusions: High-frequency rTMS over left DLPFC improves cognitive control and reduces symptoms in methamphetamine use disorder. Effects relate to cortical oscillations, identifying targets for precision treatment. Unilateral left DLPFC stimulation outperforms bilateral and control protocols, supporting biomarker-guided personalized neuromodulation for addiction.

Disclosure: Nothing to disclose.

40.3 Determining the optimal TMS protocol to modulate the reward positivity: the path to theoretical and clinical precision

Travis Baker

Rutgers University, Center for Molecular and Behavioral Neuroscience, Newark, New Jersey, United States

Background: An electrophysiological phenomena associated with the reward function of the anterior midcingulate cortex (MCC)—the reward positivity—have provided extensive empirical insight into individual differences in reinforcement learning, aging, and psychiatric conditions. Because TMS offers a powerful tool for investigating causal brain-behavior relations, its experimental and clinical application may help provide a deeper understanding of the functional significance of the reward positivity in health and disease. In this talk, I will provide evidence from a large TMS parameter search for the optimal TMS targeting and pulse protocol for MCC modulation (NCT06695884).

Methods: To identify the optimal targeting protocol, 35 nicotine users were randomly assigned to Active (n = 17) or Sham (n = 18) TMS. We then utilized neuroimaging methods to construct individualized targets based on prefrontal structure, function(fMRI), and connectivity with the MCC. Then across two TMS sessions, 1000 rTMS pulses were delivered at 10-Hz continuously over each Target while we recorded EEG from participants performing a reward task. Next, we tested the effects of various TMS pulses protocols (10-Hz rTMS, intermittent TBS [600, 1200 pulses], and continuous TBS [600, 3600 pulses) on the reward positivity. 50 nicotine users were recruited and assigned to a pulse protocol (excitatory or inhibitory) group, and completed two sessions.

Results: Overall, the Active TMS group displayed a larger RewP compared to the Sham TMS group, p < .0001. When comparing across Targets, DWI targeting displayed the largest effect size (d = 1.5) compared to all other targets (d < 0.8). Next, 10-Hz rTMS produced the largest excitatory effect on RewP amplitude (p < 0.05), while both TBS protocols either reduced (iTBS; p < 0.05) or had no effect (cTBS pulses: p > 0.05) on RewP amplitude. Finally, when testing brain-behavior relationships, increasing RewP amplitude was associated with enhance reward learning, while reducing RewP amplitude was associated with a decrease in effortful behavior.

Conclusions: The findings presented here potentially offer bidirectional TMS effects on MCC reward function that are spatially and cognitively precise, and provide best practices to choose stimulation parameters that will advance the treatment for neurocognitive processes involved in MCC dysfunction.

Disclosure: Nothing to disclose.

40.4 Error processing is a viable cognitive target for neuromodulation in substance use disorder

Vaughn Steele

Yale University School of Medicine, Hartford, Connecticut, United States

Background: Error processing is a dysregulated cognitive function in substance use disorders (SUDs) that could be a target for intervention. Differences between SUD samples and community controls (CC) are often identified in error processing tasks as measured with event-related potentials (ERPs) and functional magnetic resonance imaging (fMRI). We summarize 2 cohorts to identify specific neural correlates of error processing and 2 cohort where we modulated error processing with repetitive transcranial magnetic stimulation (rTMS).

Methods: We present evidence from ERPs (SUD N = 82, CC N = 89) and fMRI (SUD N = 31; CC = 30) outlining dysregulated neural correlates of error processing in SUD compared to CC. Then, we present 2 SUD cohorts with ERP (N = 21) and fMRI (N = 31) evidence that error processing in SUDs is modulatable with rTMS. ERPs and fMRI were measured while participants completed common tasks that elicit error processing (Go/NoGo; Stop Signal Reaction Time Task). In the rTMS groups, a cupcake design was implemented with ERP or fMRI collected before and after a single session of rTMS to measure the acute effects of rTMS. We applied a single session of intermittent theta-burst stimulation (a form of rTMS) to the left dorsolateral prefrontal cortex with neuronavigation. Error processing was quantified by neural activity elicited by an error. Theta frequency was extracted from the ERP measure and BOLD signal was extracted from dorsal anterior cingulate cortex (dACC) in the fMRI data.

Results: Hypoactivation was identified in the SUD group, compared to CCs, in both theta, t(169) = 4.14, p < 0.001, d = 0.63, and dACC, t(40.6) = 2.01, p = 0.052, d = 0.63, measures highlighting dysregulation of error processing in SUD groups. Importantly, theta power increased post-rTMS, t(20) = 2.66, p = 0.015, d = 0.79, and the hypoactive dACC BOLD signal normalized post-rTMS, relative to controls, t(56.1) = 0.81, p = 0.423, d = 0.215. Together, these results highlight the potential of rTMS as a safe and effective interventional technique to normalize error processing in SUD.

Conclusions: Overall, we present evidence that error processing is dysregulated in SUD as measured with ERPs and fMRI and these processes are modulatable with rTMS. We argue this as a safe and effective tool to target cognitive functions beyond craving in SUD samples which could lead to positive behavior change.

Disclosure: Nothing to disclose.

Study Group

41. Unlocking Clinical Mechanisms Through Animal Models: A Wellcome Initiative

Susannah Tye, Helen Mayberg, Suresh Sundram, Rachel Hill, Sophie Erhardt, Susanne Ahmari, Jared Young

Queensland Brain Institute, The University of Queensland, St Lucia, Australia

Study Group Summary: Animal models remain indispensable tools for investigating how specific genetic, environmental, and developmental risk factors disrupt brain function and behaviour, and for evaluating novel therapeutics in psychiatry. However, with the proliferation of hundreds of single- and multi-hit models, the field faces a critical and timely challenge: how do we identify and select the most appropriate model for a given mechanistic hypothesis or clinical phenotype?

The Consortium for Preclinical Psychiatric Research (CPPR), a new Wellcome Trust initiative, seeks to systematically evaluate and rank existing animal models across core symptom domains of depression, anxiety, and psychosis. The goal is to create an interactive, web-based platform that guides researchers in selecting behavioural assays and models aligned with their specific research questions.

This initiative arrives at a pivotal moment for translational neuroscience, as the field moves toward precision psychiatry, circuit-based treatment approaches, and AI-driven discovery pipelines. To remain relevant, animal research must evolve to incorporate:

• Bi-directional feedback loops between clinical and preclinical research,

• Systems neuroscience tools that map circuit dysfunction, and

• Mechanistic alignment with neuromodulatory and pharmacological targets.

This session will bring together CPPR and College members from diverse Background:s and career stages to present emerging frameworks for model evaluation, with an emphasis on interdisciplinary, collaborative development, and an invitation for ongoing contributions.

The discussion will explore strategies to:

• Enhance the predictive validity and reproducibility of animal models,

• Incorporate AI and lived experience perspectives into model curation, and

• Improve alignment with biomarker-informed therapeutic development in psychiatry.

With translational momentum accelerating the integration of neuroscience and psychiatry, this discussion is both timely and closely aligned with ACNP’s mission. Contributions from the College membership is vital to shaping the future of translational psychiatric research, and the CPPR offers a unique forum through which to do this.

Disclosure: Nothing to disclose.

Mini Panel

42. Crossing Death Valley: Translational Approaches to Psychiatric Disorders

42.1 Rescuing dendritic inhibition for cognitive remediation across brain disorders

Abstract Not Included

42.2 Microbial allies in utero: probiotics as translational tools against prenatal stress

Tamar Gur

Ohio State University College of Medicine, Columbus, Ohio, United States

Background: Prenatal stress is a pervasive risk factor with well-documented consequences for offspring, including heightened vulnerability to psychiatric disorders. Emerging evidence from our lab and others highlights the gut microbiome as a critical mediator of neurodevelopmental trajectories during gestation. Our previous work identified microbes that metabolize tryptophan to be reduced in both human and rodent studies of prenatal stress. Here we address if targeting tryptophan metabolism through of use of probiotics or specific tryptophan metabolites during pregnancy may prevent the negative sequelae of prenatal stress.

Methods: Pregnant C57/BL6 females were randomly assigned to stressed or non-stressed control groups. In addition, mice received either of the Trp-metabolizers, P. excrementihominis (Pe), Bifidobacterium dentium (Bd) or saline vehicle control. Mice were randomly assigned to the following groups: non-stressed/vehicle, stressed/vehicle, non-stressed/Pe, stressed/Pe, non-stressed/Bd, and stressed/Bd. Vehicle, Bd, Pe mice received gavage on E10-E16. LC-MS/MS was used to quantify tryptophan metabolites. Behavior tests included light-dark box for anxiety and three chamber box test for social preference.

Results: PNS increased fetal microglia (n = 8–9; p < 0.05) in all offspring. The females exhibited higher baseline microglia abundance. Pe gavage reduced anxiogenic behavior in adult offspring and increased distance traveled in adult female offspring (n = 5–7; p < 0.05). Pe reduced fetal CCL2 (n = 8–10, p < 0.05) and abrogated PNS-induced increases in tryptophan and kynurenine (n = 7–8, p < 0.05). Bd treatment partially abrogated PNS-induced reductions in litter weight gain (n = 5–7, p < 0.10), while also increasing sociability and social novelty in non-stressed mice (n = 7–11, p < 0.05). The sociability outcomes were dominantly observed in male mice only (n = 3–5, p < 0.05), while the social novelty was an effect primarily demonstrated in females (n = 2–6, p < 0.05). Bd also increased indole-3-propionic acid in the maternal and fetal plasma as well as indole-3-acetic acid in the maternal plasma.

Conclusions: Prenatal stress alters fetal microglia and tryptophan metabolism, with sex-specific behavioral outcomes. Microbiome-targeted interventions like Pe and Bd mitigate these effects, highlighting their translational potential.

Disclosure: Nothing to disclose.

42.3 Targeting amygdala neuropeptide pathways to regulate fear across species: lessons learned

Abstract Not Included

Panel

43. The Claustrum: A New Player in Pain and Opioid Addiction and Relapse

43.1 Overview of claustrum anatomy, physiology, and function

Abstract Not Included

43.2 Claustro-cortical circuit in acute and chronic pain

Anna Taylor

University of Alberta, Edmonton, Canada

Background: The claustrum is a subcortical structure reciprocally connected to the cortex. While its function remains debated, early studies point to regulation of cortical network activity that supports normal sensory processing. I will present new data on how diverse claustro-cortical circuits control acute and chronic pain in mouse models.

Methods: Male and female C57Bl6/J mice were used. Retrograde dye tracing was used to identify populations of claustrum neurons that target the anterior cingulate (ACC) and prelimbic cortex (PrL) (n = 16, 8 F). Spatial transcriptomics (multiplex in situ hybridization) was performed to identify claustrum opioid receptors (n = 4, 2 F). Next, mice (n = 32, 16 F) received a retroAAV into the ACC or PrL followed by a floxed DREADD (HM4Di or HM3Dq) into the claustrum. A final group (n = 8, 4 F) received viral intracranial injections followed by a hind paw injection of complete Freund’s adjuvant (CFA). Following recovery, a vehicle or DCZ (1 mg/kg, i.p.) was injected and the impact on acute and chronic pain was assessed. Following testing, brains were isolated and the impact of chronic pain on claustrum activity (using Fos) and opioid receptor expression was determined.

Results: ACC and PL received inputs from largely non-overlapping populations of claustrum cells. Transcripts for all four opioid receptors were in claustrum cells. While mu, delta, and ORL1 transcripts were in both inhibitory and excitatory cells, kappa transcripts were only in excitatory cells. Inhibition of claustrum-ACC cells, but not claustrum-PrL cells, significantly reduced nociceptive thresholds (FDCZxvirus(10,105) = 6.0, p < 0.0001). Inhibition of either pathway did not alter nociceptive thresholds in hypersensitive hind paw CFA mice (F(3,28) = 2.37, p = 0.09). Activation of the claustrum-PrL, but not the claustrum-ACC pathway, reversed pain hypersensitivity (FDCZxvirus(5,84) = 7.35, p < 0.0001). Finally, chronic pain resulted in reduced cFOS expression in kappa receptor expressing claustrum cells (F(2,23) = 11.62, p = 0.0003).

Conclusions: The claustrum can be segregated based on projection pathways and opioid receptor expression. These separate pathways serve distinct functions in acute and chronic pain. Chronic pain leads to adaptations in these functions, potentially driven by changes in opioid receptors.

Disclosure: Nothing to disclose.

43.3 Claustrum circuits controlling oral fentanyl self-administration

Ami Citri

The Hebrew University of Jerusalem, Jerusalem, Israel

Background: The claustrum has been implicated in executive function and impulse control. Claustral subnetworks can be defined by connectivity or gene expression. These networks exert differential, potentially opposing regulation over behavior. Here, we addressed the roles of claustrum neurons projection to the anterior cingulate cortex vs. kappa-opioid receptor (KOR)-expressing claustral neurons in regulating opioid consumption.

Methods: We used Fos staining, snRNA-seq, smFISH and fiber photometry in male and female mice to address the identity and activity of claustral populations. Optogenetic manipulations and constitutive inhibition were applied to probe the function of claustral populations in oral fentanyl self-administration.

Results: Fentanyl exposure (0.3 mg/kg i.p.) induced c-Fos expression in 25% of claustral neurons, with frontal-projecting neurons comprising 60% of Fos+ cells (F(1, 5) = 231.21), p = 2.2e-05, ANOVA on linear-mixed model). In contrast, as assayed both by single-cell profiling and smFISH, KOR-expressing claustral neurons were depleted for IEG expression (p < 0.001, x-stat = 17.5; χ²). Co-recording CLA_KOR vs ACCp neurons, we observed that the two populations transitioned between periods of correlated and inversely correlated activity. Specifically, while ACCp neurons exhibited dips of activity ‘framing’ bouts of oral fentanyl self-administration, CLA_KOR neurons exhibited acute elevations of activity prior to every consummatory lick (n = 5 mice ACCp; n = 4 CLA_KOR). While chronic inhibition of ACCp neurons increased fentanyl bout consumption (25 ± 2 mL vs. control 13 ± 1 mL; t = 3.992, p = 0.0015; n = 7–8 mice/group), preliminary observations demonstrate a reduction in consumption following chronic inhibition of CLA_KOR neurons (n = 4 mice). Optogenetic stimulation of ACCp neurons reduced the probability that mice will consume in a bout of multiple rewards (bout probability: no laser: 70% ± 5%; laser: 36% ± 11%; t = 3.38, p = 0.028, n = 5 mice), while preliminary evidence demonstrates that optogenetic stimulation of CLA_KOR neurons elicits the opposite effect, increasing consumption (n = 3 mice).

Conclusions: Our results indicate that while ACCp neurons act as a brake on opioid consumption, activity of CLA_KOR neurons is permissive for consumption.

Disclosure: Nothing to disclose.

43.4 Claustrum circuits associated with incubation of oxycodone seeking after voluntary abstinence

Kenichiro Negishi

IRP, NIDA, NIH, Baltimore, Maryland, United States

Background: High relapse rates characterize opioid addiction. In humans, abstinence often occurs voluntarily due to the negative consequences of drug seeking. To model this condition, we developed a rat model of incubation of oxycodone seeking following electric barrier-induced voluntary abstinence. We recently identified a critical role for the claustrum in this incubation (Negishi et al., J Neurosci 2025). The claustrum sends projections to multiple cortical areas, including anterior cingulate cortex (ACA) and retrosplenial cortex (RSP). We are currently studying the role of these claustral projections in incubation.

Methods: We trained rats (n = 18; 8 females) to self-administer oxycodone (0.1 mg/kg/infusion, 6-h/day) for 14 days. We then induced abstinence by introducing an electric barrier of increasing intensity near the drug-paired lever. On abstinence days 1 and 20, we tested the rats for oxycodone seeking under extinction conditions (no shock, no drug). We injected cholera toxin B subunit (CTb) into ACA or RSP for dual retrograde tracing and used Fos as an activity marker to examine if claustrum-to-ACA and claustrum-to-RSP projections were activated during the relapse (incubation) test on day 20. We also measured Fos expression in ACA and RSP. For controls, we used rats that underwent oxycodone self-administration and electric barrier-induced abstinence but were not tested for relapse before brain extraction.

Results: As in previous studies, the rats showed robust incubation of oxycodone seeking (higher lever presses on abstinence day 20 than on day 1; F(1,17) = 15.6, p = 0.001). This incubation was associated with increased Fos expression in claustrum (F(1,16) = 31.0, p = 0.001) and ACA (F(1,16) = 19.6, p = 0.001), and in claustrum-to-ACA (F(1,16) = 4.8, p = 0.043) and claustrum-to- RSP (F(1,15) = 4.2, p = 0.058) projections, measured by percentage of Fos/CTb double-labeled cells in claustrum. We are currently using chemogenetics to test if inhibition of ACA, and claustrum-to-ACA and claustrum-to-RSP projections, decreases incubation.

Conclusions: Incubation of opioid seeking after voluntary abstinence is associated with activation of claustro-cortical projections, suggesting that these projections contribute to relapse vulnerability.

Disclosure: Nothing to disclose.

Panel

44. Smartphones, Sensors, and Social Media: Applying AI to Neuroscience to Identify Psychiatric Risk Across Development

44.1 Sentiment analysis of the caregiving environment as an early, objective, and scalable predictor of child psychopathology

Lauren Henry

National Institute of Mental Health, Bethesda, Maryland, United States

Background: The caregiving environment is a critical factor in psychiatric disorder development; early, objective, and scalable assessments are nascent. We obtained natural, daylong audio recordings of young children’s environments. Using artificial intelligence (AI), we generated transcripts and conducted sentiment analysis to examine relations with later psychopathology.

Methods: 356 children oversampled for irritability (45.8% female, Mage = 14.7 mos) and their mothers (Mage = 31.4 yrs, 50.6% White) enrolled. At baseline, families completed natural, daylong audio records via the Language ENvironment Analysis system. We measured irritability via parent report (Multidimensional Profile of Disruptive Behavior-Infant-Toddler) and a standardized lab task (Disruptive Behavior Diagnostic Observation Schedule). One year later, mothers completed structured interviews of child psychopathology (Preschool Age Psychiatric Assessment). In a subset (n = 153) of the sample, we generated transcriptions with WhisperX (machine learning model, OpenAI) and a score representing negative (−1), neutral (0), and positive (+1) sentiment for each line of text using Llama (Large Language Model, Meta). We computed an average sentiment score for each tape.

Results: We generated transcripts from 1,103 hrs of audio (per tape M = 14.70, SD = 2.95). Average sentiment scores were close to neutral (M = 0.05, SD = 0.11). In zero-order correlations, sentiment scores were unrelated to parent-reported and lab-based child irritability. In linear regression analyses, sentiment of the caregiving environment contributed unique information in the prediction of internalizing symptoms one year later, relative to parent-reported and lab-based child irritability. That is, more negative sentiment predicted more internalizing symptoms, β = −0.23, p = 0.04, F(5,73) = 3.29, p = 0.01, adj R2 = 0.13. Greater irritability via parent report (β = 0.46, p < 0.001), but neither sentiment nor lab task, predicted externalizing symptoms one year later, F(5,73) = 5.46, p < 0.001, adj R2 = 0.22.

Conclusions: As early as the second year of life, a more negative caregiving environment derived using daylong, natural audio and AI, shows specificity for predicting later internalizing (but not externalizing) symptoms. Results have implications for developing scalable, early risk assessments for psychopathology.

Disclosure: Nothing to disclose.

44.2 Smartphone sleep metrics detect suicide risk and anhedonia among adolescents

Jaclyn Kirshenbaum

Columbia University, New York, New York, United States

Background: Over the past decade, suicide deaths in adolescents have significantly increased and sleep health has worsened. Social anhedonia is a related risk factor for suicide. Understanding how sleep contributes to proximal suicidal thoughts and behaviors (STB) and related risk factors (i.e., anhedonia) is critical to identify targets of intervention using unobtrusive and scalable tools. We aimed to test in two high-risk cohorts of 13–18-year-old adolescents, whether sleep features measured via smartphone sensors and experience sampling relate to proximal STB and social anhedonia.

Methods: High-risk youth (N = 145, 112 female, 114 with STB) installed the Effortless Assessment Research System (EARS) application on their smartphones, allowing access to motion data over 6 months. Participants were sent weekly prompts regarding STB. Clinical interviews measured suicidal events (i.e., attempts, psychiatric hospitalizations and emergency department visits for suicide-related concerns) at 1-, 3-, and 6-month follow-ups. Mixed-effects logistic regressions tested whether weekly sleep duration and bedtime related to next-week STB. A separate sample of youth oversampled for MDD (N = 154, 110 female, 95 with past/current depression) were prompted via experience sampling regarding their sleep quality, duration, social anhedonia, and affect for three weeks throughout a 12-month study. Multilevel linear regressions examined the association between daily subjective sleep items (i.e., quality, duration) and social anhedonia.

Results: In high-risk suicidal adolescents, a 1 standard deviation increase in weekday sleep duration related to 2-folds greater odds of a next-week suicidal event (OR = 2.39, 95% CI [1.19, 4.44], p = 0.013). In youth oversampled for MDD, greater sleep duration on weekdays related to next day social anhedonia when positive affect was low (B = −0.07, 95% CI[−0.12, −0.02], p = 0.007).

Conclusions: Results reveal that smartphone-derived sleep duration on weekdays related to a higher risk for suicidal events. Longer sleep duration on weekdays also related to greater social anhedonia, which could reflect reduced motivation and increased isolation. Future larger studies may leverage smartphone sensors to test anhedonia as a mechanism explaining the association between sleep problems and proximal suicide risk in adolescents.

Disclosure: Nothing to disclose.

44.3 Technology in OCD care: quantitative analysis of sleep and alcohol use and qualitative exploration of perspectives and experiences with technology

Adam Frank

Keck School of Medicine University of Southern California, Los Angeles, California, United States

Background: The expansion of digital tools is theorized to intersect with symptoms of obsessive-compulsive disorder (OCD), while allowing for longitudinal assessments. Wearable devices and smartphone-based apps can monitor symptoms, physiology, and behavioral patterns. Patterns of alcohol use in individuals with OCD are understudied. We used self-report and wearable data to explore patterns of alcohol use in adults with OCD. In a separate cohort, we also sought to understand how technology contributes to, reinforces, or complicates OCD symptom cycles, assessed through semi-structured qualitative interviews.

Methods: Smartphone-based daily diaries were completed for 10 weeks assessing symptom burden, alcohol use and sleep, and paired with wearable data from Fitbit Charge 5. Adults with OCD (N = 18) were compared to healthy controls (HC, N = 16). We used dynamic multilevel structural equation modeling with Bayesian estimation to analyze lagged and concurrent effects with assessments nested within people. Separately, 27 virtual, semi-structured interviews were conducted to explore technology use and OCD symptoms. Interviews were transcribed, de-identified, coded, and analyzed using a constructivist grounded theory framework.

Results: Significantly more days with drinking occurred in adults with OCD (d = .31, t = −7.00, p < .0001). Within individuals, each additional hour of self-reported sleep was associated with a small but significant increase in alcohol use the same day (b = 0.199, SE = 0.082, p = .020). The average minutes asleep via Fitbit was not different between OCD and HC cohorts (406.6 and 400.5, respectively, p = 0.201). Qualitatively, participants describe 1) a robust relationship between technology and OCD symptoms characterized by disturbing-thoughts, 2) technology interactions driven by obsessions related to order, completeness, or “just-right” sensations, 3) digital hoarding and technology-related superstitions.

Conclusions: We investigated alcohol consumption in adults with OCD using mobile technologies in naturalistic settings and found associations between sleep and alcohol intake. Our qualitative results illustrate how technologies can serve as both triggers and tools for compulsive behavior among individuals with OCD, particularly in the context of disturbing-thought-based and “just-right” symptom dimensions.

Disclosure: Abbott Labs, Contracted Research, Self

44.4 Digital despair and digital recovery: language-based markers of psychological risk in U.S. opioid mortality

Brenda Curtis

NIH, Baltimore, Maryland, United States

Background: Opioid poisoning mortality (OPM) remains a major U.S. public health crisis, shaped by psychological, economic, and social distress—not just drug supply. These upstream factors are hard to track at scale. This study tests whether digital language—specifically, community-level psychological markers from Twitter—can predict opioid mortality and reveal signals of risk and resilience.

Methods: We analyzed over 1.5 billion tweets from 6 million U.S. users mapped to 662 counties, matched to age-adjusted county-level opioid mortality data from the CDC. The Linguistic Inquiry and Word Count lexicon was applied to extract 73 psychologically meaningful language categories from Twitter data. These features were entered into multivariate linear regression models predicting OPM, controlling for county-level sociodemographic covariates (e.g., income, education, rurality). Standardized regression coefficients were computed, and p-values corrected using Benjamini-Hochberg false discovery rate.

Results: Negative affective language strongly predicted higher opioid mortality: LIWC categories ANXIETY, SAD, and NEGATIVE EMOTION were most predictive (p < 0.001). Words such as “afraid,” “worthless,” and “hate” were frequent in high-mortality counties. Conversely, protective language included MONEY, RELIGION, and POWER, suggesting that expressions of structure, meaning, and agency are associated with lower mortality. The final model explained 41% of the variance in county-level OPM (R² = .41). These findings demonstrate that linguistic signals of despair and resilience can be meaningfully identified at scale using social media data.

Conclusions: Community-level language reveals latent psychological states associated with population health outcomes. By applying psychologically grounded language models to social media, we can surface interpretable indicators of behavioral health risk and protection. These findings illustrate the promise of digital phenotyping for scalable, unobtrusive population monitoring. Building on this foundation, we are developing a national infrastructure to extend these insights to the individual level using integrated behavioral, linguistic, and clinical data. This work paves the way for future applications in relapse prediction, treatment personalization, and proactive public health response.

Disclosure: Nothing to disclose.

Panel

45. Cross-Species Approaches Using Functional Brain-Based Biomarkers to Address Translational Gaps in Psychiatry

45.1 Altered visual processing biomarkers in humans and mice after serotonergic psychedelics point to a reorganization of cortical feedback circuitry

Jordan Hamm

NYU School of Medicine and Nathan Kline Institute, New York City, New York, United States

Background: Like many rapid-acting antidepressant treatments, psilocybin stimulates the growth of dendritic spines in medial prefrontal cortex (mPFC). This effect is seen in two major subtypes of pyramidal neurons: subcortical-projecting pyramidal tract neurons (PTs) and cortical-projecting intratelencephalic neurons (ITs). While the PT-plasticity may under stress-related effects, the functional consequence of IT neuron plasticity is unknown. Here we test how perceptual functions known to depend on mPFC feedback projections to visual cortex (VC) via IT neurons are altered by a dose of a serotonergic psychedelic in humans and mice.

Methods: In 16 humans who had recently taken a serotonergic psychedelic (PSY; 7m; LSD or psilocybin) and 16 age/sex-matched controls (CNT; 6m), saccade latencies and EEG were measured during a predictive saccade task and a visual oddball paradigm. During the same oddball paradigm, 11 mice given DOI or psilocybin and 7 given saline had local field potentials recorded in VC and in ACa, an mPFC region that projects to VC. Activity patterns in axonal projections from ACa to VC were measured with 2-photon Ca++ imaging in 5 mice.

Results: Psilocybin and LSD in humans a) altered predictive processing in a saccade task, and b) reduced EEG visual mismatch responses during a visual oddball task (delta power to deviant vs neutral stimuli; F(1,28) = 4.68, p < = 0.039). These effects correlated with days since dose (r = 0.53, p = 0.03), resolving after ≈7 days. In mice, psilocybin and DOI similarly reduced visual mismatch responses in VC (deviant vs neutral stimulus; t(20) = 2.44, p = 0.035). Further, ACa to VC functional connectivity was reduced in the week after a dose (granger causality; t(12) = 2.58, p = 0.02). Finally, ACa-V1 networks showed decreased precision (cell-cell correlations D = 5.48) and broad hyperactivation in DOI vs saline (F(1,491) = 6.62, p = 0.01). No sex effect trends were found.

Conclusions: Past pre-clinical translational work has focused on stress-related phenotypes and a role for cortical-subcortical circuits. This study highlights a novel transpecies biomarker of psilocybin's lasting impact on information processing—visual deviance detection—and identifies a cortico-cortical mechanism—reorganized top-down feedback circuits—that might link cell, circuit, and perceptual effects of psilocybin treatments.

Disclosure: Nothing to disclose.

45.2 Coupled sleep oscillations correlate with memory across humans and rats and are evoked by closed-loop auditory stimulation during sleep

Bryan Baxter

Massachusetts General Hospital, Charlestown, Massachusetts, United States

Background: The coupling of cortical slow oscillations, thalamocortical sleep spindles, and hippocampal ripples are implicated in sleep-dependent memory consolidation. Coupled oscillations may function as biomarkers of memory consolidation. We performed a cross-species examination of the relation between sleep oscillations and memory and examined the effect of closed-loop auditory stimulation during sleep (CLASS) on these oscillations. CLASS is a noninvasive neuromodulation approach that can improve memory in humans

Methods: Humans (n = 17; 12F) with epilepsy undergoing presurgical evaluation using scalp and stereotactic EEG with hippocampal contacts were trained on the Motor Sequence Task in the evening and were tested the following morning. Rats (n = 7) implanted with tetrode arrays in the retrosplenial cortex and hippocampus were given a 2-hr sleep opportunity between training and testing on the object place recognition task. Slow oscillations and spindles were detected from the cortex and ripples were detected from the hippocampus during non-rapid eye movement (NREM) stage 2 (humans) and NREM (rats) using validated algorithms. Coupling was defined as the temporal co-occurrence of oscillations. In a separate cohort of healthy humans during daytime naps (n = 10; 5F) and rats (n = 5), CLASS, consisting of quiet 50ms pink noise stimuli, was delivered during the upstate of NREM slow oscillations.

Results: The percentage of spindles coupled with slow oscillations and hippocampal ripples correlates with memory in humans (F(12) = 4.91, p = 0.047, r = 0.49) and the density of spindles that were coupled with slow oscillations or with ripples shows a trend towards correlating with memory in rats (F(12) = 3.88, p = 0.07). In our preliminary findings, CLASS evokes an event-related potential in the slow wave band in both species, but there was an increase in spindle activity only in humans (humans: F(17) = 4.52, p = 0.048; rats: F(9) = 0.56, p > 0.05) compared to sham.

Conclusions: This work illustrates a cross-species translational pipeline to uncover electrophysiological biomarkers of memory consolidation during sleep that could serve as targets when developing interventions for memory deficits. CLASS is used as an example intervention that engages sleep oscillations though further analyses are needed to understand species specific differences in the response.

Disclosure: Nothing to disclose.

45.3 From preclinical models to humans: translational approaches for mechanistically distinct psychoactive compounds

Nina Dedic

Gilgamesh Pharmaceuticals, New York, New York, United States

Background: NMDAR antagonists, serotonergic psychedelics and the oneirogen ibogaine, have demonstrated rapid and sustained therapeutic effects in clinical trials. While these agents reliably elicit subjective effects indicative of CNS target engagement, quantifiable pharmacodynamic measures are needed to guide dosing and patient stratification. We describe the translational strategy for two novel, mechanistically distinct compounds: GM-1020, an orally bioavailable NMDAR antagonist in Phase 2 for MDD, and GM-3009, an ibogaine analogue and KOR agonist in preclinical evaluation for substance use disorders.

Methods: GM-1020 (0.1–10 mg/kg) was assessed in the FST and CMS paradigm using sucrose intake, elevated plus maze, and novel object recognition. GM-3009 (1–10 mg/kg) was evaluated in opioid self-administration and reinstatement (oxycodone, morphine, heroin and/or fentanyl). Target engagement was assessed in vitro and/or in vivo by radioligand binding ([³H]MK-801 for NMDAR and [³H]U-69593 for KOR) and functional assays. EEG was recorded in freely moving rats. A Phase 1 study of oral GM-1020 (20–360 mg) in healthy volunteers evaluated safety, PK, and PD including resting-state EEG, 5D-ASC, and CADSS.

Results: GM-1020 dose-dependently decreased immobility in the FST and reversed CMS-induced anhedonia, anxiety-like behavior, and cognitive deficits (p < 0.05). GM-3009 reduced opioid self-administration and cue-induced reinstatement across opioids. EEG analyses revealed distinct spectral profiles: GM-1020 reduced theta-beta and increased gamma power, while GM-3009 elevated theta and high gamma power. Predicted RO at minimally efficacious doses was 20–30% (NMDAR, GM-1020) and 25–50% (KOR, GM-3009), corresponding to plasma Cmax of ~90–350 ng/mL and ~65–200 ng/mL, respectively. In humans, GM-1020 showed a clear PK/PD relationship, with plasma Cmax correlating with EEG and subjective effects. Reductions in alpha and beta power and increases in gamma power were dose-dependent (p < 0.001) and observed at plasma levels overlapping with efficacious exposures in rodents.

Conclusions: Both drug candidates showed robust PK/PD relationships. GM-1020 EEG effects translated to humans, supporting its utility as a biomarker for dose selection and mechanistic differentiation in the development of psychoactive drugs.

Disclosure: Gilgamesh Pharmaceuticals, Employee, Self, Gilgamesh Pharmaceuticals, Stock / Equity - Privately Held Company, Self

45.4 Translational biomarker discovery and validation for ALTO-101, a PDE4 inhibitor being developed for cognitive impairment associated with schizophrenia

Patricio O'Donnell

Alto Neuroscience, Cambridge, Massachusetts, United States

Background: Identifying pharmacodynamic (PD) biomarkers for novel treatments addressing cognitive deficits in schizophrenia would increase the efficacy of developing those agents. We sought to identify and validate electroencephalography (EEG) biomarkers linked to cognitive performance in a public patient dataset, reproduce them in preclinical models, and test them as PD markers for ALTO-101, a novel phosphodiesterase 4 (PDE4) inhibitor we are developing for the treatment of CIAS.

Methods: BSNIP 1 and 2 study data were analyzed (625 patients with schizophrenia, 641 controls), dividing data were divided into discovery and validation sets for replication and focusing on EEG and event-related potentials (ERPs).

We explored the effect of ALTO-101 in rats (n = 14) EEG to evaluate whether ALTO-101 improved features identified in humans. Animals were treated with three doses of ALTO-101 (0.003 mg/kg; 0.03 mg/kg, and 0.1 mg/kg i.p.), along with vehicle or MK-801 (0.1 mg/kg i.p.) in a crossover design.

We analyzed EEG and ERP data from a randomized placebo-controlled Phase 1 clinical trial that evaluated cognitive and behavioral effects of ALTO-101 (0.5 and 1.5 mg) in healthy volunteer (n = 40).

Results: In the BSNIP data discovery set, theta inter-trial coherence (ITC) in response to stimuli during the oddball task showed the largest case-control differences (effect sizes −0.65 to −0.91) and was strongly associated with cognitive measurements, particularly processing speed (partial r = 0.13 to 0.27). The findings were replicated in the validation set (case-control effect sizes - 0.70 to −0.94, cognition correlations partial r = 0.12 to 0.21).

ALTO-101 enhanced theta ITC dose-dependently in MK-801-treated rats (p < 0.001 for the highest dose; effect size = 0.73), indicating this is a viable PD biomarker for ALTO-101 in a brain with altered excitation/inhibition balance.

In the phase 1 trial, tan increase in theta ITC was the most prominent response (d = 1.05, p = 0.00004).

Conclusions: Task-related theta responses were altered in patients with schizophrenia and correlated with cognitive measures. Back-translated to rodents revealed a PD effect of ALTO-101, which improved the PD marker in a Phase1 trial. The data indicate that EEG signals reflecting impaired circuit function can be used as PD biomarkers in a translational manner for developing novel drugs.

Disclosure: Alto Neuroscience, Employee, Self, Alto Neuroscience, Stock / Equity - Publicly Traded Company, Self

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46. 22q11.2 Deletion Syndrome as a Window Into the Neurobiology of Psychosis: From Molecules to Patients

46.1 Cortical oscillatory dynamics and their link to sensory and behavioral deficits in 22q11DS

David Parker

Emory University, Athens, Georgia, United States

Background: 22q11.2 deletion syndrome (22q11DS) is one of the strongest genetic risk factors for psychosis. Resting-state neural oscillations, which reflect excitatory-inhibitory (E/I) balance, are increasingly implicated in psychosis pathophysiology. We hypothesized that altered oscillatory dynamics and E/I balance mediate the link between sensory processing deficits and broader behavioral phenotypes in 22q11DS.

Methods: 31 individuals with 22q11DS (mean age = 31, 13F) and 25 healthy controls (mean age = 32, 14F) completed cognitive and symptom assessments, and eyes-open EEG during resting state and an auditory deviance task (16 sensors). Resting EEG was analyzed using a sliding-window multitaper FFT (1–55 Hz), with power averaged across sensors and canonical bands. Alpha-band functional E/I ratio (fE/I) was computed as the correlation between short-windowed amplitude and the normalized fluctuation function (nF(t)) of the 8–13 Hz envelope; values < 1 and > 1 reflect inhibition- or excitation-dominated states. ERPs and time-frequency responses were derived using a modified Morlet wavelet, with mismatch responses calculated as deviant minus standard. Group differences and mediation between power, fE/I, auditory responses, cognition, and symptoms were examined.

Results: 22q11DS showed increased power in low (delta, theta: d = 0.85, 0.78) and high frequencies (high beta, gamma: d = 0.67, 0.74), and elevated alpha-band fE/I (d = 1.06). ERP/time-frequency analyses revealed enhanced responses to standard tones (|d| = 0.92, 1.06) and reduced novelty responses (|d| > 1.08). The group also showed lower cognitive scores (d = −2.29) and higher prodromal symptom scores (d = 1.48). Increased early response to standard tones (60–120 ms), indicating reduced stimulus-specific adaptation, was associated with poorer cognition and partially mediated by elevated fE/I (β = 0.21, 95% CI [0.07, 0.40], p = .0024). Lower responses to deviance mismatch responses (3–17 Hz and 290–430 ms) were associated with poorer cognition and partially mediated by elevated delta power (β = 0.15, 95% CI [0.01, 0.32], p = .036)

Conclusions: These findings suggest that altered resting-state dynamics and E/I imbalance may underlie sensory and cognitive dysfunction in 22q11DS, with implications for E/I-targeted interventions in both 22q11DS and idiopathic psychosis.

Disclosure: Nothing to disclose.

46.2 Cortical structural variability implicates excitatory/inhibitory imbalance and disrupted circuit activity in 22q11.2 deletion syndrome

Carrie Bearden

University of California at Los Angeles, Los Angeles, California, United States

Background: 22q11.2 deletion syndrome (22q11DS) is associated with widespread cortical alterations, but the neurobiological underpinnings are unclear. Here, we examined patterns of regional alteration in both mean differences and variability in cortical structure, and how these relate to neurotransmitter receptor density and neural oscillatory dynamics.

Methods: Structural MRI data on 438 22q11DS (mean age = 18.3; 52% females, 52 with psychosis) and 412 controls (mean age = 20.8; 48% females) were analyzed. Mean and dispersion estimates of cortical thickness (CT) were calculated using double generalized linear models across 68 regions of interest. Results were corrected with false-discovery rate (FDR) threshold of q < 0.05. Cortical maps of mean and dispersion differences between 22qDel vs controls were spatially correlated, using spin permutation testing, with mean receptor distribution maps (i.e., NMDA and GABAergic) and band-specific electrophysiological signal power.

Results: 22qDel carriers showed widespread regionally higher CT relative to controls (β = 0.14 to 0.72). Greater dispersion (within-group variability) was found in the left precentral gyrus (β = 0.46), right rostral anterior cingulate cortex (β = 0.44)) and right entorhinal cortex (β = 0.48) in 22qDel vs controls. Greater mean group differences in CT spatially overlapped with regions with higher densities of NMDA (r = 0.43, p < 0.001) and GABAergic receptors (r = 0.39, p = 0.001). Cortical regions showing greater dispersion in 22q11DS vs controls spatially overlapped with regions of lower levels of GABAergic receptors, where delta and high-gamma frequencies are strongest, and alpha and beta frequencies are weakest.

Conclusions: 22q11DS patients had the most pronounced CT differences in cortical regions enriched in glutamatergic and GABAergic receptors. Spatial transcriptomic analyses further indicate that greater heterogeneity may preferentially emerge in cortical regions with lower inhibitory neurotransmission, as indicated by GABAergic, alpha and beta bands (frequencies associated with sensory inhibition and top-down control), and in regions involved in large-scale coordination and local circuit activity. Together, these findings implicate excitatory/inhibitory imbalance and disrupted functional circuitry in 22q11DS.

Disclosure: Nothing to disclose.

46.3 Investigating convergent bioenergetic dysfunction in 22q11Del and 3q29Del

Ryan Purcell

Virginia Tech, Roanoke, Virginia, United States

Background: Rare genetic variants that confer high risk for schizophrenia may present opportunities to understand the molecular trajectory of human neurodevelopmental risk for psychosis. The two strongest known risk variants for schizophrenia are deletions at human chromosome 22q11 and 3q29. We have engineered either of these two copy number variants into an isogenic cohort of induced pluripotent stem (iPS) cell lines and differentiated them to dorsal forebrain cortical organoids to determine how these variants alter early cortical development.

Methods: Copy number variants were engineered into an iPS cell line from a neurotypical donor using CRISPR/Cas9. Breakpoints were determined and a lack of off-target structural variation was validated through Bionano genome-wide optical mapping. Organoids were differentiated by dorsal cortical patterning. Organoid proteomes were quantified by tandem mass tag mass spectrometry at early developmental time points. Proteome alterations were determined by weighted co-expression network analysis (WGCNA). Specific protein results were validated by targeted immunoblotting.

Results: We found that while most WGCNA modules were altered by time point, only a single module (M41) was significantly altered by genotype. This module contains nearly 90% mitochondrial proteins. Analysis of differential expression (DEx) by genotype revealed that both 22q11 and 3q29 DEx proteins were enriched with mitochondria-localizing proteins. We tested whether 22q11 and 3q29 produced dysregulation of similar proteins and found significant overlap among commonly increased (40x enriched, p < 0.0001) and decreased (31x enriched, p < 0.0001) proteins. The 32 commonly increased proteins were significantly enriched for pathways related to mitochondrial gene expression and translation whereas the 44 commonly decreased proteins were enriched for mitochondrial energy production pathways.

Conclusions: In an isogenic cohort of iPS cell derived human cortical organoids, the 22q11 and 3q29 deletion produce similar proteomic dysregulation, which disproportionately impacts neural mitochondria. Ongoing studies are aimed at determining the functional effects of these protein changes.

Disclosure: Nothing to disclose.

46.4 Aberrant glutamatergic transmission and homeostatic plasticity in 22q11DS: insights from human iPSC models

Zhexing Wen

Emory University School of Medicine, Atlanta, Georgia, United States

Background: 22q11.2 Deletion Syndrome (22q11DS), the most prevalent chromosomal microdeletion disorder in humans (incidence ~1 in 4,000 live births), arises from hemizygous deletions of a 1.5–3.0 Mb region on chromosome 22. Notably, 20–30% of individuals with 22q11DS develop schizophrenia (SCZ) by early adulthood, making 22q11DS one of the strongest genetic risk factors for SCZ. However, the pathophysiological mechanisms by which 22q11.2 deletion disrupts neuronal function and contributes to the psychotic symptoms of 22q11DS remain poorly understood.

Methods: In this study, we generated multiple iPSC lines from clinically well-characterized individuals with 22q11DS and age- and sex-matched healthy controls. These iPSCs were then differentiated into 2D cortical neurons or 3D cortical organoids. Whole-cell patch clamp recordings were performed on neurons from 2 to 8 weeks after differentiation to assess the intrinsic membrane properties, excitatory synaptic transmission and homeostatic plasticity, followed by the spearman correlation analysis of neuronal phenotypes and psychosis-related clinical and psychophysiological measures. Furthermore, synaptosomes were extracted from both control and 22q11DS cortical organoids for integrative analysis of the mRNA and microRNA profiling, and a microRNA-gene regulatory network was then constructed at the pathway level.

Results: Cellular and electrophysiological analyses revealed that 22q11DS neurons exhibit hyperexcitability, reduced glutamatergic synaptic transmission, and impaired homeostatic synaptic plasticity. Spearman correlation analysis revealed significant associations between neuronal phenotypes and psychosis-related clinical and psychophysiological measures, including the Structured Interview for Prodromal Syndromes (SIPS), cognition, and mismatch negativity (MMN). Integrative transcriptomic analysis revealed dysregulated microRNAs—downregulation of hsa-miR-185-5p and hsa-miR-128-3p, and upregulation of hsa-miR-214-3p—in 22q11DS neurons that are mechanistically linked to synaptic dysfunction and impaired plasticity.

Conclusions: Our findings demonstrated aberrant synaptic transmission and impaired homeostatic plasticity in 22q11DS neurons and revealed microRNA-driven gene regulatory networks contributing to the synaptic pathology.

Disclosure: Nothing to disclose.

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47. Microdosing Psychedelics: Is It Effective? Is it a Placebo? Is it Safe?

47.1 Preliminary findings from an ongoing survey on self-administered psilocybin microdosing practices and effects

Kim Kuypers

Maastricht University, Maastricht, Netherlands

Background: Microdosing psychedelics, repeated low-dose use, has gained scientific and media attention. Our lab's controlled studies reveal acute cognitive and brain changes, with notable individual variability. While preparing a clinical trial to explore this further, we are also studying real-world microdosing practices, focusing on users’ dose choices and comparisons to clinical protocols.

Methods: Participants self-enrolled in a Dutch microdosing program to identify their optimal psilocybin dose from mushrooms or truffles, aiming to improve personal outcomes such as mood. After informed consent, they completed surveys before titration, on dosing days, and after the dosing period, including questions on dosing practices and VAS ratings of drug effects and changes in perception, mood, cognition, and well-being. Doses were categorized as low, medium, or high based on mushroom/truffle weight. Kruskal–Wallis tests assessed VAS differences across dose levels, with significant effects followed by pairwise Mann–Whitney U tests comparing baseline to dose, applying Bonferroni correction.

Results: To date, 46 participants completed baseline assessments, with 30 completing the study and included in analyses (mean age 47.4 (±10.6); 90% female; all with tertiary education); 66.7% identifying an amount that produced positive effects without notable impairment. Most (83.3%) dosed every other day, choosing average optimal amounts of 0.62 g (±0.58) dried mushrooms and 0.86 g (±0.36) fresh truffles.

Kruskal–Wallis tests showed significant Dose effects on Anxiety (H(3) = 12.90, p = 0.005), Productivity (H(3) = 9.12, p = 0.028), and Feeling Close to Others (H(3) = 10.13, p = 0.017). Compared to baseline, low (p = 0.006) and medium doses (p = 0.029) reduced Anxiety, while high doses increased Productivity (p = 0.016) and Feeling Close to Others (p = 0.022). Chi-square tests showed no differences between doses in psychological or physical adverse effects.

Conclusions: These preliminary findings reveal real-world psilocybin microdosing patterns, showing dose self-titration with a preference for medium doses that balance benefits and minimal disruption. Dose-dependent effects on anxiety, productivity, and social connectedness emphasize the need for personalized dosing and bridge clinical trials with natural use.

Disclosure: MindMed Inc, Contracted Research, Self

47.2 Safety and efficacy of microdosing LSD to treat major depressive disorder: results from a pilot and a randomised, triple-blind, active placebo-controlled, parallel groups trial

Dimitri Daldegan-Bueno

School of Pharmacy, The University of Auckland, Auckland, New Zealand

Background: Major depressive disorder (MDD) affects approximately 5% of the global population. Classic psychedelics have shown promise in treating various mental health disorders. We present results of microdosing LSD as a treatment for major depressive disorder first, in an open-label phase 2A trial (LSDDEP1) to assess safety and tolerability, then in a larger phase 2b triple-blind, active placebo-controlled, parallel groups trial (LSDDEP2) to determine the superiority of LSD versus placebo.

Methods: In both trials, participants underwent an 8-week LSD microdosing regimen using the titratable MB-22001 formulation, taking two doses a week (18 doses). Fifteen doses were self-administered at home, and one was taken at the clinical research centre. The initial dose was 8 μg, and the following ones were titratable from 4 to 20 μg based on subjective perception and tolerability. For LSDDEP2, caffeine or methylphenidate was used as an active placebo. Safety measures included adverse events, blood laboratory tests, electrocardiography (ECG), and echocardiography (LSDDEP1 only). The main efficacy outcome was measured using the Montgomery-Åsberg Depression Rating Scale (MADRS) at baseline and at the end of treatment (8 weeks).

Results: Nineteen participants (15 male) participated in LSDDEP1. No serious or severe adverse events and clinical alterations in safety measures were observed. One participant withdrew due to experiencing anxiety when dosing. MADRS scores were reduced by 59.5% (baseline mean: 23.7, SD = 6.72) at the end of the intervention (measure mean: 9.59, SD = 7.67) and were sustained for up to six months. For LSDDEP2, recruitment is finished (n = 89), but the data will only be analysed after unblinding (second semester 2025).

Conclusions: While limited by an open-label design and small sample size, results from the pilot trial provide preliminary evidence supporting the safety and feasibility of treating moderate depression with microdosed LSD and underscore a need for further randomised controlled trials. It is also the first study to evaluate valvulopathy after repeated psychedelic administration in humans. Upcoming results from the larger, placebo-controlled trial will shed light on the efficacy of microdosing LSD to treat depression.

Disclosure: Nothing to disclose.

47.3 Lasting Effects of a low dose of LSD vs placebo on depressive symptoms

Harriet de Wit

University of Chicago, CHICAGO, Illinois, United States

Background: Many people who practice ‘microdosing’ claim that LSD, even at low doses, can improve mood. We recently reported that a single, low dose of LSD (26 µg), compared to placebo, produced lasting improvement in symptoms 48 hours after ingestion in individuals with depressed mood. Because symptoms of depression are heterogeneous, we examined in greater detail which items showed improvement after the drug. Here we present an unpublished item analysis of symptom improvements 48 hours after the drug or placebo, on the Beck Depression Inventory II (BDI-II).

Methods: Men and women who reported depressive symptoms at baseline (BDI-II score ≥17; n = 20) participated in a randomized, double-blind, crossover study in which they received a single dose of LSD (26 µg) and placebo. Subjective and mood measures were assessed during the two 5-hour sessions, as well as 48-hrs after each session. In the present analysis, we compared individual items on the BDI-II 48 hours after the LSD or placebo sessions, using t-tests and a modified ‘momentary’ version of the BDI-II.

Results: BDI-II depression scores declined significantly at 48 hours after LSD, compared to placebo (p < 0.05). Item-level analysis of BDI scores after the doses revealed that two symptoms were most responsive to LSD (26 µg) relative to placebo: reductions in negative affect (i.e., life dissatisfaction, mean change score = −0.450, p = 0.004, Holm-Bonferroni corrected) and sleep disturbance (mean change score = −0.450, p = 0.02, Holm-Bonferroni corrected). Items least affected by low dose LSD included cognitive and affective symptoms related to self-perceived physical appearance (p = 0.8), suicidal ideation (p = 0.6) and work productivity (p = 0.6).

Conclusions: These findings suggest that the acute low dose of LSD (26 µg) may have therapeutic potential both by reducing negative affect and by improving sleep-related symptoms of depression. The changes in sleep are consistent with findings of Allen et al. (2024) reporting improvements in sleep the day after low-dose LSD dosing. An important future direction will be to investigate these effects on sleep and to determine their relation to the improvements in negative affect.

Disclosure: Pharmala Biotech, Board Member, Self

47.4 Assessing the potential cardiovascular risk of microdosing the psychedelic LSD in mice

Scott Thompson

University of Colorado School of Medicine, AURORA, Colorado, United States

Background: Serotonergic psychedelics, such as psilocybin and LSD, are potent agonists at many serotonin receptors (5HTRs), including the 5HT2ARs, which mediate their subjective effects, and 5HT2BRs, which cause the heart damage from the anorexigenic compound fenfluramine. Microdosing, or the chronic consumption of a sub-hallucinogenic dose of a psychedelic, typically LSD or psilocybin, has gained popularity due to anecdotal accounts of emotional and cognitive benefits, without alterations of consciousness. It is not known whether chronic microdosing can damage the heart.

Methods: We performed echocardiography on adult mice before and after 8 weeks of administration of LSD (0.01 and 0.03 mg/kg), saline, and 5HT (40 mg/kg) or fenfluramine (10mg/kg) as positive controls, to measure structural and functional properties of the hearts. LSD at these doses elicits a very small head twitch response, indicating low levels of 5HT2AR activation.

Results: We observed decreases across time for ventricular inner diameter, increases in posterior wall thickness, and decreases in ventricle volume after 5HT, but not in vehicle or LSD groups. No changes in ejection fraction or fractional shortening were observed in any group. We also observed increased regurgitation fraction after fenfluramine, but not after vehicle or LSD.

Conclusions: We found no evidence of structural or functional cardiovascular pathology after prolonged administration of low-dose LSD in mice. The lack of effects of LSD were not due to differences in its efficacy or affinity at mouse 5HT2BRs, compared to humans. The metabolism of LSD is faster in mice than in humans, which decreases its ability to activate 5HT2BRs chronically. We thus attribute the absence of cardiovascular pathology after microdosed LSD to insufficient levels of 5-HT2BR receptor occupancy. An essential caveat of this preclinical work is that although we have no evidence that microdosing LSD results in cardiac pathology in mice, we cannot therefore conclude that the human microdosing of LSD is safe. Microdosed psychedelics could be dangerous in people with pre-existing cardiovascular risk factors. Prospective studies should be performed to determine whether microdosed psychedelics produce cardiac pathology in humans.

Disclosure: ProNovo Therapeutics, Founder, Self, Terran Biosciences, Consultant, Self, Otsuka, Consultant, Self

Panel

48. Biological Pathways of Psychiatric Risk and Resilience: Multi-System, Cross-Species Evidence for Stress Vulnerability and Adaptation

48.1 Sex-specific impact of early life and adolescent stress on the brain vascular properties and involvement in mood disorders vs resilience

Caroline Menard

Université Laval, Quebec City, Canada

Background: The blood-brain barrier (BBB), a dynamic frontier formed by endothelial cells, astrocytes and pericytes, mostly develops during embryonic stages, but maturation and refinement still occur after birth. In mice, vascular density increases along with pericyte coverage of vessels during the first weeks of life while cerebral blow flow is reduced in adolescence. Despite major changes in the brain vascular morphology and function during these time sensitive developmental periods, it is unknown when the BBB acquires adult-like properties and if it could be more vulnerable to environmental challenges. Stressful events in childhood or adolescence are strongly associated with the development of psychiatric conditions, increased reactivity to future stressors, and mounting evidence supports a role for neurovascular alterations in mood disorders and stress resilience.

Methods: Development of the BBB was characterized in the prefrontal cortex (PFC), a hub for mood and emotion regulation, by combining behavioral, transcriptomic and morphological studies for male and female mice at 1) baseline condition, 2) after 10-day exposure to early life stress (ELS, maternal separation/limited bedding and nesting) or 15-day adolescent stress in which animals were subjected to social instability and isolation. Serum samples are also analyzed to establish blood signatures of stress responses and identify vascular biomarkers that will be validated on human cohorts exposed to ELS or adolescent stress.

Results: BBB molecular profile in the PFC is not stable throughout development. Expression of Cldn5, a tight junction essential for maintenance of BBB integrity, and genes linked to endothelial cell-pericyte communication (Pdgfb, Pdgfrb) fluctuates in a sex-specific manner. These patterns are disrupted by ELS and adolescent stress along with the development of anxiety and depression-like behaviors. We expect loss of pericyte coverage and BBB hyperpermeability in line with elevated blood markers of vascular dysfunction (E-selectin, PDGF-BB) in susceptible but not resilient individuals.

Conclusions: Our study provides the first characterization of BBB maturation from childhood to adolescence in a sex-specific manner and the impact of stress during two sensitive periods of early life. We believe that it will inform on novel mechanisms and diagnostic tools.

Disclosure: Nothing to disclose.

48.2 Early adversity disrupts molecular and neural pathways underlying adolescent addiction susceptibility

Rodrigo Grassi-Oliveira

Aarhus University, Porto Alegre, Brazil

Background: Early life stress (ELS) significantly increases risk for substance use disorders (SUD), yet underlying neurobiological mechanisms remain unclear. Here, we test whether conserved molecular pathways connect early adversity, prefrontal dysfunction, and susceptibility/resilience to substance use.

Methods: C57BL/6JRj mice (both sexes; n = 12–14/group) were exposed to ELS from PND 2 to 13 via limited bedding and maternal separation (3 h/day). Controls remained undisturbed. Adolescent behavior included Y-maze, novelty-suppressed feeding, and cocaine-conditioned place preference (CPP). After CPP, mPFC and brain-derived extracellular vesicles (BDEs) were collected for targeted transcriptomic profiling.

Human data were from the Brazilian High-Risk Cohort for Childhood Psychiatric Disorders (BHRC; n = 467), a longitudinal pediatric sample followed from childhood to adolescence. Peripheral blood DNA methylation (EPIC v2 array) and multimodal MRI (FreeSurfer, FSL) were collected. Early adversity and substance use related problems were quantified using validated instruments.

Results: In male mice, ELS increased cocaine-CPP (p < 0.001), suggesting enhanced drug-context learning. Transcriptomic profiling revealed differentially expressed genes related to synaptic signaling and glial development (e.g., Grm2, Efna5, L1cam, Sox10). In BHRC adolescents, preliminary analyses suggest ELS may be associated with differential methylation in stress-regulatory genes and reduced ventromedial prefrontal cortical thickness (p < 0.05, FDR-corrected). Ongoing moderation analyses explore whether ELS modulates methylation–brain associations linked to SUD risk. Although this study primarily focuses on vulnerability, the variability in behavioral and molecular responses to ELS—observed both in mice and humans—raises the possibility that some individuals may exhibit resilient phenotypes. We are currently examining whether specific transcriptomic or epigenetic patterns in non-susceptible animals and low-risk adolescents under adversity could represent biological substrates of resilience.

Conclusions: These findings support a translational model in which ELS alters molecular and neural pathways involved in addiction vulnerability or resilience, offering targets for early detection and prevention.

Disclosure: Nothing to disclose.

48.3 Biological pathways linking early adversity to risk and resilience in the development of psychopathology: DNA methylation, inflammation, child maltreatment and social support

Colter Mitchell

University of Michigan, Ann Arbor, Michigan, United States

Background: Child maltreatment is a pervasive issue with long-lasting effects on physical and mental health. Inflammation profiles and DNA methylation scores are increasingly used to examine the biological embedding of early adversity. Meanwhile, social support has been posited as a protective factor that might mitigate the adverse effects of maltreatment on these biological markers. Our study investigates the relationship between child maltreatment, inflammation, DNA methylation scores, and the potential buffering role of social support.

Methods: We use a longitudinal representative panel comprising 1875 individuals tracked from birth young adulthood. Data on child maltreatment were obtained via Parent-Child Conflict Tactics Scales at ages 3, 5, 9, and 15. DNA methylation scores ((epigenetic clocks, immune scores, and CVD scores) were derived from salivary DNA collected at ages 9 and 15 and blood DNA at age 22. DNA methylation scores. Age 22 blood samples measure inflammation markers (C-reactive protein and IL-6 and the O-link inflammation panel). Social support measured perceived support from friends, family, and significant others at ages 9, 15, and 22.

Results: Physical assault at age 3 years was positively associated with increased biological age for PCPhenoAge (β = 0.073; 95% CI, 0.019–0.127), DNAm Immune Latent Factor (β = 0.102; 95% CI, 0.09–0.12) and increased rate of aging in DunedinPACE. Emotional aggression at age 3 years was positively associated with PCPhenoAge (β = − 0.107; 95% CI, −0.162 to −0.052) and DNAm Immune Latent Factor (β = 0.05; 95% CI, 0.03–0.08). Emotional neglect at age 5 years was positively associated with PhenoAge. Cumulative exposure to physical assault between ages 3 and 5 years was positively associated with Dunedin Pace; emotional aggression was negatively associated with Dunedin PACE. Current work is finalizing results for immune response at age 22. Children with higher levels of social support had substantially lower effects of child maltreatment on these biomarkers.

Conclusions: Our findings underscore the profound biological impact of child maltreatment as evidenced by altered inflammation profiles and DNA methylation scores. Social support mitigates these adverse biological changes, highlighting its potential as a an intervention aimed at reducing the long-term health impacts of early adversity.

Disclosure: Nothing to disclose.

48.4 Attenuated trauma-predictive brain network as an adaptive marker of stress resilience

Felicia Hardi

Yale University, New Haven, Connecticut, United States

Background: Trauma is a significant risk factor for psychiatric disorders and can alter neural responses to future stress. However, the mechanisms underlying the dynamic interaction between past trauma and subsequent stress remain unclear.

Methods: We first identified a brain network associated with lifetime trauma exposure. Using a machine learning approach, we trained and tested functional connectivity networks to predict past traumatic life events in a community sample of adults (N = 170; Mage = 26; 60% female). We then evaluated the response of the trauma-predictive brain networks to acute emotional and physiological stressors in two separate experiments. In the first experiment using a subsample of participants (N = 92; Mage = 25; 59% female), trauma-predictive brain networks were examined following a randomized acute stress induction. In the second independent crossover study (N = 27; Mage = 28; 41% female), trauma-predictive networks were examined following a pharmacological (hydrocortisone) administration. Finally, to examine the significance of resulting neural response for psychiatric disorders, we examined how neural patterns following stress relate to depressive symptoms. All studies included both sexes.

Results: Connectome-based predictive modeling successfully predicted past trauma exposure (rs = 0.41, pperm < 0.001). Brain network associated with higher trauma showed high involvement of salience network connections, with model prediction driven by connectivity in the medial frontal, salience and default mode networks, motor regions, and cerebellum. Notably, network connectivity within the trauma-predictive network was attenuated following acute stress relative to control (b = −0.09, pFDR = 0.021; pperm < 0.001, permutation test). A similar pattern was observed in the pharmacology sample, with decreased connectivity under hydrocortisone compared to placebo within this trauma-predictive network (pperm < 0.001). Notably, attenuated trauma-predictive network connectivity after acute stress was associated with lower depressive symptoms in the stress-exposed group (p = 0.038), but not control. All models adjusted for sex and motion.

Conclusions: Stress induced blunted connectivity of the trauma-related brain networks, and this reduced engagement may reflect an adaptive regulatory mechanism in response to future stress.

Disclosure: Nothing to disclose.

Mini Panel

49. Olfactory Pathways Into the Mind: A Gateway to Psychiatric Disorders

49.1 Human peripheral olfactory pathobiology

Abstract Not Included

49.2 Contribution of olfactory inputs to prefrontal cortex activity and social cognition in mice

MInghong Ma

University of Pennsylvania, Philadelphia, Pennsylvania, United States

Background: Despite strong clinical links between smell deficits and psychiatric disorders, a conceptual framework for explaining the impact of olfactory processing on higher brain functions remains lacking. The mammalian olfactory system transmits odor information and respiration-entrained signals to non-olfactory regions, including the medial prefrontal cortex (mPFC), which regulates cognition, emotion, and social behaviors. However, the neural circuit that connects the olfactory system with the mPFC remains elusive, and this study aims to identify such a circuit and its impact.

Methods: Multiple approaches are utilized in this study, including gene editing, neural circuit tracing, optogenetics, chemogenetics, patch clamp, fiber photometry, and mouse behavior (three-chamber test for social motivation and social recognition).

Results: Several neural pathways can potentially transmit olfactory inputs into the mPFC, and here we focus on the olfactory bulb (OB)—anterior olfactory nucleus/tenia tecta (AON for simplicity)—mPFC pathway. Using a mouse line that allows genetic access to AON neurons, we identified the mPFC as the primary neocortical target of AON projection. Optogenetic activation of AON neurons elicited excitatory postsynaptic currents (EPSCs) in mPFC pyramidal neurons (77.3% in infralimbic versus 42.9% in prelimbic). In contrast, optogenetic inactivation of AON neurons reduced spontaneous EPSCs in about half of the mPFC neurons. Furthermore, mPFC-projecting AON neurons were active during social investigation. Finally, chemogenetic inhibition of mPFC-projecting AON neurons impaired social recognition without altering social motivation.

Conclusions: Our study reveals direct anatomical and functional synaptic connections from the AON to mPFC, and this pathway plays a critical role in social recognition.

Disclosure: Nothing to disclose.

49.3 The inflammatory pathology in the olfactory epithelium: a contributor to clinical manifestations in patients with psychotic disorders via the olfactory-prefrontal circuit

Abstract Not Included

Panel

50. Decoding the Addicted Brain: Single-Cell and Spatial Transcriptomics at the Intersection of Drug Use and HIV

50.1 3D Mapping the addicted brain: spatial disruption of nucleus accumbens (NAc) microcircuits by opioids and HIV

Lauren Wills

Icahn School of Medicine at Mount Sinai, New York, New York, United States

Background: Opioid use disorder is a leading cause of preventable death. HIV positive individuals experience higher rates of overdose and lower utilization of replacement therapies. Little is known about how opioid exposure, in the context of HIV, reshapes brain circuits implicated in addiction. This presentation will highlight gene dysregulation and spatial niche disruption in the addiction-relevant brain region, the NAc, in the context of HIV.

Methods: Single-nuclei RNA seq (snRNA-seq): EcoHIV inoculated mice were permitted to self-administer oxycodone (0.05–0.3mg/kg/inf, N = 12). Following euthanasia, the NAc was dissected and subject to snRNA-seq. Data were analyzed by customized Scanpy pipeline.

STARmap 3D : Oxycodone (5mg/kg) was injected into mice daily for 4 days (N = 4). Brains were removed, dissected into a 50μm slab containing the NAc, then subject to hydrogel embedding, clearing and sequencing. Data were analyzed by customized pipeline and Pyxa studio.

Results: We identified clusters of D1- and D2-receptor-expressing populations of medium spiny neurons (MSNs) (p < 1 × 10⁻³²⁴, t-test). D1 and D2 MSNs showed phenotype-dependent gene dysregulation. Pathway analyses indicated oxycodone promoted transcriptional changes linked to netrin-1 signaling and neuronal projection in D1 and D2 MSNs, with D2 MSNs exhibiting changes associated with substance misuse. HIV promoted changes related to impaired coordination in D2 MSNs. D2 MSNs were impacted by the HIV/oxycodone combination, with pathway analyses highlighting gene programs linked to viral infection. These findings suggested that D2 MSNs may be vulnerable to both HIV and opioids. With STARmap 3D and ONTrac trajectory analysis we predicted three initial layers of complexity in the z-axis of the NAc - primary excitatory neurons, interneurons, and a final layer of D1/D2 MSNs. 3D walkthrough highlighted intricate spatial organizations and enabled visualizations of non-neuronal cells within the broader cellular architecture.

Conclusions: We identified unique changes in NAc MSN populations in response to oxycodone, HIV, or their combination. D2 MSNs were more sensitive to these perturbations than D1. We initiated efforts to characterize MSNs within their 3D context—an essential step toward leveraging NAc architecture to develop novel therapeutics at the HIV–addiction interface.

Disclosure: Nothing to disclose.

50.2 Brain-wide characterization of single cell multiomic changes during chronic HIV infection and cocaine self-administration in mice

Hongkui Zeng

Allen Institute for Brain Science, Seattle, Washington, United States

Background: Previous studies have highlighted the reciprocal exacerbation of symptoms between substance use disorder (SUD) and HIV, suggesting that these conditions develop within shared neurobiological systems. However, due to limited systematic animal research, our understanding remains elusive. As part of the Single Cell Opioid Responses in the Context of HIV (SCORCH) consortium, we conducted comprehensive single-nucleus RNA sequencing (snRNA-seq) and multiomic profiling to characterize cell-type-specific transcriptional and epigenetic changes in addiction-related brain regions of EcoHIV-infected mice that compulsively self-administer cocaine under either restricted or extended access conditions.

Methods: We generated a large-scale (>650) 10x snRNA-seq and multiome libraries across 10 broad brain regions. After stringent data QC, we mapped QC-passed cells onto the latest Allen Brain Cell atlas and identified ~120 neuronal and non-neuronal subclasses in prefrontal cortex, hippocampus, amygdala, striatum, pallidum, lateral septum, thalamus, hypothalamus, and ventral midbrain.

Results: We identified differentially expressed genes (DEGs) and differentially accessible chromatin regions across sex, reinforcer, and HIV status within each cell type. Among neurons, numerous cocaine-induced up- or down-regulated DEGs (across different sex/HIV groups) were particularly enriched in (i) D1/D2 medium spiny neurons in both dorsal and ventral striatum, (ii) hippocampal pyramidal neurons, and (iii) intratelencephalic and corticothalamic pyramidal neurons in the medial prefrontal cortex. Among non-neuronal cells, oligodendrocytes, specific astrocyte subpopulations, endothelial cells, and microglia exhibited significant cocaine-induced transcriptional changes. Notably, in microglia, many immune response genes, as well as Ccr5 (a key co-receptor for HIV entry into cells), were upregulated, suggesting a potential mechanistic link between SUD and HIV pathophysiology.

Conclusions: Our dataset provides a comprehensive foundation for understanding multiomic changes associated with chronic HIV infection and cocaine addiction. These findings offer valuable insights into the neurobiological interactions between HIV and SUD that may lead to future therapeutic interventions.

Disclosure: MapLight Therapeutics, Advisory Board, Self

50.3 Single-cell RNA long-read sequencing in SIV Infection and following chronic morphine exposure in hippocampus reveals widespread dysregulation of splicing and suggests intervention strategies

Hagen Tilgner

Weill Cornell Medicine, New York, New York, United States

Background: The intertwined epidemics of Human Immunodeficiency Virus (HIV) infection and Opioid-use disorder (OUD) present significant public health challenges. HIV can lead to neurological complications, and opioid misuse may exacerbate these effects. It is postulated that latent HIV persists in the brain despite antiretroviral therapy (ART) and it occurs in some brain regions involved in opioid addiction.

Methods: We collected macaque hippocampal tissue of 5 conditions (SIV only, SIV with ART, SIV and Morphine, Morphine and control, N = 4/group). We profiled these samples using single-cell multiome technology. We enriched for 3,225 genes using exon-junction spanning probes and sequenced the resulting libraries on an Oxford Nanopore PromethIon.

Results: We find hundreds of splicing events dysregulated by SIV, chronic morphine exposure, SIV + ART or SIV+morphine across hippocampal cell types. In multiple cell types, we find that most SIV-dysregulated exons are rescued by ART treatment. In accordance with microglia as a potential reservoir for HIV, microglia are an exception to this rule, with < 20% of SIV dysregulated exons rescued by ART. A microglial subpopulation in SIV conditions is associated with these persistent changes. Strikingly, ART induces many splicing alterations itself to the point that SIV + ART reveals more splicing dysregulation than SIV alone. In excitatory neurons, 62% of SIV + ART-dysregulated exons maintain control-like isoform patterns across other cell types, supporting the feasibility of cell-type-agnostic therapeutic correction. We also found several splicing factors differentially expressed upon SIV infection and similarly rescued by ART. Moreover, we found strong splicing dysregulation by morphine and partially converging SIV and Morphine splicing defects on SIV-dysregulated exons. Surprisingly, morphine also rescues approximately one-third of SIV-dysregulated splicing events, suggesting that such events may be dysregulated by overall virus-induced inflammation rather than directly by the virus.

Conclusions: Our results reveal RNA splicing as strongly affected by SIV, chronic morphine exposure and ART. This work provides potential intervention strategies to address ART-associated splicing changes and the shared dysregulation caused by SIV and opioid exposure.

Disclosure: Nothing to disclose.

50.4 Cell-type-specific vulnerabilities and molecular mechanisms in substance use and HIV-associated neurodegeneration revealed by single-cell multiomics

Manolis Kellis

Massachusetts Institute of Technology, Cambridge, Massachusetts, United States

Background: HIV and substance use disorders (SUDs) frequently co-occur, with ~17% of the ~15 million global injection drug users living with HIV. HIV itself increases risk for opioid use due to chronic pain syndromes in people with HIV (PWH). Despite antiretroviral therapy, HIV-associated neurocognitive disorders (HAND) remain common, driven by viral effects, immune activation, and neuroinflammation. These processes converge with mechanisms in SUDs, Alzheimer’s disease (AD), and psychiatric disorders—including immune dysregulation, synaptic dysfunction, and neuronal injury—contributing to cognitive decline. The SCORCH consortium integrates single-cell transcriptomic and epigenomic data across HIV and SUD populations, along with AD and PsychENCODE datasets, to define shared and distinct cellular pathways in neuroHIV and addiction.

Methods: We performed large-scale single-nucleus RNA (snRNA-seq) and ATAC (snATAC-seq) sequencing on postmortem brain tissue from 184 individuals across five diagnostic groups: control, OUD, CUD, PUD, and HIV. We profiled ~6 million nuclei from regions implicated in neuropsychiatric and neurodegenerative conditions, including frontal and insular cortices, putamen, and nucleus accumbens. We defined 8 major cell classes, 32 subclasses, and 61 subtypes. Cross-species validation was performed using a rodent intravenous self-administration (IVSA) model.

Results: We identified strong region- and cell-type-specific molecular alterations. Medium spiny neurons (MSNs) in the nucleus accumbens exhibited marked transcriptional dysregulation in OUD. HIV infection induced glial reactivity, immune activation, senescence, and epigenomic erosion. GWAS enrichment highlighted a specific MSN subtype as a hub for opioid genetic risk. Rodent IVSA models confirmed conserved transcriptional signatures of addiction. Integration with AD, bipolar disorder, and schizophrenia datasets revealed shared neuroimmune and neurodegenerative pathways.

Conclusions: This unified single-cell multi-omic framework reveals how SUDs and HIV impact the brain at cellular resolution. The resulting atlas provides a foundational resource for investigating mechanisms and developing precision therapies for neuroHIV and addiction.

Disclosure: Nothing to disclose.

Mini Panel

51. Exploring the Therapeutic Potential of Mebufotenin (GH001) Across Depressive Disorders

51.1 GH001 provides rapid and significant antidepressant effects in patients with treatment-resistant depression: efficacy and safety results from a phase 2b, double-blind, randomized controlled trial with a 6-month open-label extension

Lisa Harding

Mood Institute, Milford, Connecticut, United States

Background: There is a large unmet need for treatments that offer rapid and sustained improvement in patients with treatment-resistant depression (TRD). Early-stage trials in patients with TRD suggest that GH001, a synthetic form of mebufotenin for pulmonary inhalation, may have the potential to induce ultra-rapid improvement in depressive symptoms. Here, we describe safety and efficacy of GH001 in patients with TRD enrolled in a Phase 2b multicenter trial.

Methods: This trial (NCT05800860) included a 7-day, randomized, double-blind part (Part 1) and an open-label extension (OLE) with up to five GH001 re-treatments over 6 months. In Part 1, patients were randomized 1:1 to receive an individualized dosing regimen (IDR) of up to three escalating doses of GH001 (6, 12, and 18 mg) or placebo on a single day with a 1-hour interval between doses. Administration of subsequent doses in the IDR was based on patients’ subjectively reported psychoactive effects and safety and tolerability of previous dose(s). Montgomery–Åsberg Depression Rating Scale (MADRS) scores were assessed on Day 1 (baseline and 2 hours post-dose), Day 2, and Day 8 by a rater who was blind to treatment assignment. In the OLE, patients were assessed for up to five GH001 IDR re-treatments over 6 months based on MADRS score and safety and tolerability of previous dose(s). The primary efficacy endpoint was mean change in MADRS total score from baseline to Day 8 versus placebo in Part 1. Safety was assessed throughout the trial. The trial was conducted under the supervision of qualified healthcare professionals, providing psychological support per standard of care, but without any planned psychotherapeutic intervention before, during, or after dosing.

Results: Eighty-one patients enrolled; 40 were randomized to GH001 and 41 to placebo in Part 1. All patients completed Part 1 and transitioned directly into the OLE. In Part 1, least squares (LS) mean (SE) change in MADRS total score from baseline to Day 8 was significantly greater with GH001 (−15.2 [1.2]; n = 40) compared with placebo (0.3 [1.2]; n = 41) (LS mean difference, −15.5; P < 0.0001), with an effect size (Cohen’s d) of −2.0. Significant reductions in MADRS total score were also observed with GH001 versus placebo at 2 hours postdose and on Day 2. Day 8 remission rates (MADRS total score ≤10) were 57.5% and 0% with GH001 and placebo, respectively, in Part 1. In the 6-month OLE, patients received an average of four GH001 treatments. Of the 63 patients who completed the OLE, 40 (63.5%) received 1 − 4 treatments. At 6 months, OLE completers had a mean (SD) MADRS total score of 9.4 (8.7), and 73.0% (n = 46) were in remission. Throughout the trial, most treatment-emergent adverse events (TEAEs) were mild or moderate. No drug-related serious TEAEs were reported in Part 1 or the OLE.

Conclusions: GH001 treatment was well tolerated and produced ultra-rapid and significant improvements in depressive symptoms in patients with TRD. These findings suggest that GH001 represents a promising novel treatment for patients with TRD.

Disclosure: Johnson and Johnson, Advisory Board, Self, Abbvie, Advisory Board, Self, Otsuka, Advisory Board, Self, Johnson and Johnson, Speakers Bureau, Self, GH, Advisory Board, Self, GH, Consultant, Spouse/Partner, Johnson and Johnson, Consultant, Spouse/Partner

51.2 Rapid improvement in anhedonia following GH001 treatment in patients with treatment-resistant depression, postpartum depression, and bipolar II disorder and a current major depressive episode

Roger McIntyre

University Health Network, Toronto,, Canada

Background: Anhedonia, a lack of interest or ability to feel pleasure in activities and experiences, is associated with risk of suicide, functional impairment, and treatment resistance in patients with major depressive disorder (MDD). Improvement in anhedonia symptoms in patients with MDD has been correlated with improvements in physical, psychological, and social functioning and quality of life. Safety and efficacy of GH001, a synthetic form of mebufotenin for pulmonary inhalation, were investigated in patients with treatment-resistant depression (TRD) in a Phase 2b trial (NCT05800860) with a 7-day, randomized, double-blind, placebo-controlled part (Part 1) and a 6-month open-label extension, and in two 7-day, Phase 2a, open-label trials in patients with postpartum depression (PPD; NCT05804708) and bipolar II disorder (BDII) and a current major depressive episode (MDE; NCT05839509). In these trials, GH001 was well tolerated, and ultra-rapid and significant reductions in Montgomery−Åsberg Depression Rating Scale (MADRS) total score were observed. In this analysis, we examined the effect of treatment with GH001 on anhedonia in patients in these three trials.

Methods: In Part 1 of the trial in patients with TRD, patients received an individualized dosing regimen (IDR) of up to three escalating doses of GH001 (6, 12, and 18 mg) or placebo on a single day. In the open-label trials in patients with PPD or with BDII and a current MDE, patients also received a GH001 IDR on a single day, with the same doses as those used in the TRD trial. MADRS assessments were conducted on Day 1 (baseline and 2 hours post-dose), Day 2, and Day 8. Anhedonia was evaluated using the MADRS 5-item anhedonia subscale (items 1 [apparent sadness], 2 [reported sadness], 6 [concentration difficulties], 7 [lassitude], and 8 [inability to feel]; subscale range: 0–30 [lower scores indicate less severe anhedonia]). Clinically meaningful improvement in anhedonia was evaluated based on a published threshold of minimal clinically important change (MCIC) of –4.6 to –5.5 points in patients with MDD.

Results: Eighty-one, ten, and six patients were enrolled in these trials in patients with TRD, PPD, and BDII and a current MDE, respectively. In Part 1 of the trial in patients with TRD, baseline mean (SD) anhedonia subscale scores were 17.6 (3.2) and 17.4 (2.6) for the GH001 (n = 40) and placebo (n = 41) groups, respectively, and changes from baseline at Day 8 were −9.9 (6.6) and 0.0 (2.3), respectively. In patients with PPD, baseline mean (SD) anhedonia subscale score was 20.8 (2.6) and change from baseline at Day 8 was −20.8 (2.6). In patients with BDII and a current MDE, baseline mean (SD) anhedonia subscale score was 19.2 (1.8) and change from baseline at Day 8 was −9.7 (6.4). In all three trials, changes in anhedonia subscale scores with GH001 treatment exceeded the MCIC at each post-dose time point (2 hours post-dose, Day 2, and Day 8).

Conclusions: Patients with TRD, PPD, or BDII and a current MDE who received GH001 as an IDR achieved ultra-rapid reductions in MADRS anhedonia subscale scores. Because the anhedonia subscale score reductions exceeded the established MCIC, the reductions in anhedonia were clinically meaningful across these depressive disorders. These findings suggest that GH001 treatment improves patients’ ability to feel pleasure and engage in activities and consequently may improve overall functioning.

Disclosure: CIHR, Grant, Self, GACD, Grant, Self, National Natural Science Foundation of China (NSFC, Grant, Self, Milken Institute, Grant, Self, Lundbeck, Consultant, Self, Janssen, Consultant, Self, Alkermes, Consultant, Self, Neumora Therapeutics, Consultant, Self, Boehringer Ingelheim, Consultant, Self, Sage, Consultant, Self, Biogen, Consultant, Self, Mitsubishi Tanabe, Consultant, Self, Purdue, Consultant, Self, Pfizer, Consultant, Self, Otsuka, Consultant, Self, Takeda, Consultant, Self, Neurocrine, Consultant, Self, Neurawell, Consultant, Self, Sunovion, Consultant, Self, Bausch Health, Consultant, Self, Axsome, Consultant, Self, Novo Nordisk, Consultant, Self, Kris, Consultant, Self, Sanofi, Consultant, Self, Eisai, Consultant, Self, Intra-Cellular, Consultant, Self, NewBridge Pharmaceuticals, Consultant, Self, Viatris, Consultant, Self, Abbvie, Consultant, Self, Bristol Myers Squibb (BMS), Consultant, Self, Atai Life Sciences, Consultant, Self

51.3 GH001 is associated with improved self-reported maternal functioning in patients with postpartum depression and rapid elimination from breastmilk

Kristina Deligiannidis

Zucker Hillside Hospital, Northwell Health, Glen Oaks, New York, United States

Background: Postpartum depression (PPD) is associated with adverse effects on maternal well-being and mother–infant relationships that can negatively impact infant development. Breastfeeding is associated with positive maternal and infant physical and mental health outcomes; however, many women with PPD postpone initiation of PPD pharmacotherapy or wean their infant sooner than planned due to concerns about medication exposure in breastmilk. In a Phase 2a open-label outpatient trial (NCT05804708) in patients with PPD, GH001, a synthetic form of mebufotenin for pulmonary inhalation, was associated with a significant reduction in mean (SD) Montgomery–Åsberg Depression Rating Scale (MADRS) total score from baseline to Day 8 of −35.4 (5.5) points; all patients were in remission (MADRS ≤ 10) by Day 8. We present additional results from this trial investigating effects of GH001 on maternal functioning following childbirth using a specifically designed, validated tool (Barkin Index of Maternal Functioning [BIMF]). To further evaluate the potential impact of GH001 on breastmilk, we report breastmilk concentrations of mebufotenin in lactating patients.

Methods: Adult patients with PPD were enrolled. Patients were administered an individualized dosing regimen (IDR) of up to three escalating doses of GH001 (6, 12, and 18 mg) on a single day (Day 1). Self-perception of maternal functioning was assessed by change in BIMF total score (range, 0–120; higher scores indicate better functioning) and functional area scores from baseline to Day 8. Concentrations of mebufotenin, its psychoactive metabolite bufotenin, and its non-psychoactive metabolite 5-methoxyindole-3-acetic acid (5-MIAA) were measured in breastmilk of lactating patients at 1 and 2.5 hours post-dose, in the evening of Day 1 (~8 hours post-dose), and on Days 2 and 8.

Results: Ten patients enrolled in the trial. Mean baseline BIMF total score was 69.7 (n = 9). At Day 8, BIMF total score increased by a mean of 34.1 points (n = 8). Higher scores were observed on Day 8 versus baseline across BIMF functional areas, including mean increases of 6.5, 5.8, 18.6, 5.8, and 10.4 points in the areas of self-care, mother–child interaction, psychological well-being, social support, and management, respectively. Of the four lactating patients, three received GH001 6 + 12 mg and one received GH001 6 + 12 + 18 mg as part of the IDR. Mebufotenin levels in breastmilk ranged from 0.24 to 3.11 ng/mL at 1 hour post-dose, from below the limit of quantification (BLQ) to 0.56 ng/mL at 2.5 hours post-dose, and from BLQ to 0.04 ng/mL at ~8 hours post-dose; all levels were BLQ on Days 2 and 8. Bufotenin was BLQ in breastmilk at all time points. 5-MIAA levels were 13.9 to 28.5 ng/mL at 1 hour post-dose, 8.1 to 13.5 ng/mL at 2.5 hours post-dose, BLQ to 0.90 ng/mL at ~8 hours post-dose, BLQ to 0.22 ng/mL on Day 2, and BLQ on Day 8. There were no serious treatment-emergent adverse events (TEAEs), and all TEAEs were mild or moderate. All patients were deemed ready for discharge within the same day of dosing.

Conclusions: In adult patients with PPD, GH001 as an IDR was generally well tolerated and was associated with improvements in all domains of self-reported maternal functioning, predominantly psychological well-being. Mebufotenin and its metabolites were rapidly eliminated from breastmilk.

Disclosure: Sage Therapeutics, Consultant, Self, Sage Therapeutics, Contracted Research, Self, Biogen, Consultant, Self, GH Research, Consultant, Self, Neurocentria, Consultant, Self, Gerbera Therapeutics, Contracted Research, Self, Reunion Neuroscience, Consultant, Self, Lipocine, Consultant, Self

Study Group

52. Autoimmune Psychosis: Myth, Anecdote, or Disease?

Belinda Lennox, Mitsuyuki Matsumoto, Katharina Schmack, Mary-Ellen Lynall, Lahiru Handunnetthi, Steven Siegel, Robert Yolken, Christopher Bartley

University of Oxford, Oxford, United Kingdom

Study Group Summary: Although rare cases of antibody-mediated encephalitis with psychiatric presentations are now well-documented, the broader construct of "autoimmune psychosis" remains a subject of debate—alternately regarded as a novel diagnostic category or a speculative extension of limited data. Clearly delineating an autoimmune subtype of psychosis would afford these individuals access to potentially disease-modifying novel therapeutics such as CAR-T cell therapies and monoclonal antibodies. This study group will critically examine the new emerging current evidence for and against autoimmunity as a driver of primary psychotic disorders, with attention to clinical phenotypes, preclinical models, biomarkers, ethical concerns and therapeutics. We will include experts in psychiatry, immunology, and neurology who will present different perspectives, drawing on published and unpublished data. Special attention will be given to the methodological challenges in distinguishing pathogenic immune processes from epiphenomena, and to the clinical implications for diagnosis and treatment. Through moderated discussion, this session will identify a set of prioritized and testable hypotheses that will help adjudicate whether autoimmune psychosis represents a valid diagnostic construct or a myth in need of dismantling.

Disclosure: Nothing to disclose.

Panel

53. Combining Species and Scales to Illuminate Sex-Biased Brain Organization and Intersections With Psychiatric Risk

53.1 Sex-specific neuroanatomical signatures of impulsivity in youth

Elvisha Dhamala

Feinstein Institute for Medical Research, Glen Oaks, New York, United States

Background: Individual differences in neural circuits underlying emotional regulation and decision-making manifest in various facets of impulsivity, which are implicated across psychiatric illnesses. While both neuroanatomy and impulsivity show sex differences, the extent to which their relationships vary across behavioral facets, neuroanatomical features, and sexes remains unclear. Understanding these multi-dimensional relationships is crucial for identifying potential biomarkers of psychiatric risk and developing targeted interventions.

Methods: Leveraging data from the ABCD Study, we examined relationships between multiple impulsivity measures (BIS/BAS and UPPS-P scales) and neuroanatomical features (cortical thickness (CT), surface area (SA), and gray matter volume (GMV)) in youth at baseline (n = 9099) and two-year follow-up (n = 6432). We used cross-validated brain-based predictive models to identify how these relationships varied across behavioral facets, neuroanatomical features, and sexes, controlling for intracranial volume where appropriate.

Results: CT predicted reward-responsiveness and drive (r = 0.044–0.093) as well as urgency measures (r = 0.055–0.078, p < 0.05) while SA and GMV broadly predicted all measures (r = 0.019–0.080, p < 0.05). These associations were generally stronger in females (r = 0.065–0.133) than in males (r = 0.031–0.072) and certain measures were only predictable in females (e.g., urgency) or in males (e.g., drive). While some impulsivity measures shared neuroanatomical substrates, others showed distinct patterns, with widespread CT effects (spanning frontal, temporal, and occipital regions) but localized SA/GMV effects (frontal and temporal poles). Notably, females showed bilateral effects while males showed more lateralized patterns.

Conclusions: These findings show that the neural basis of impulsivity varies systematically across behavioral facets, brain features, and sexes. Different components of impulsivity map onto distinct neural circuits, and these relationships show critical sex differences. The identification of these multi-dimensional relationships advances our understanding of how individual differences in the brain contribute to impulsivity and may inform the development of more targeted, sex-specific interventions for impulsivity-related disorders.

Disclosure: Nothing to disclose.

53.2 Sex differences in the human brain: from MRI to single nucleus transcriptomics

Armin Raznahan

National Institute of Mental Health, Bethesda, Maryland, United States

Background: Humans show sex-differences in numerous mental health outcomes - likely reflecting the complex interaction of biological, psychological and social factors. Mapping sex-differences in human brain organization through in vivo neuroimaging may help to unravel this complexity. However, there remains controversy regarding the extent and nature of sex-biased human brain organization from neuroimaging, and we lack information on potential cellular underpinnings of those neuroimaging sex-differences that have been reported.

Methods: This talk will present new work that (1) charts reproducible neuroanatomical sex-differences in the human brain using multiple large-scale datasets encompassing up to ~35k individuals, and then (2) conducts single nucleus RNAseq of > 1.5M cells in 180 cortical samples from 30 individuals (15 male) to resolve cell-type specific sex differences at neuroimaging hotspots of sex-biased brain anatomy.

Results: Humans show reproducible sex differences in regional brain volume that: exist above and beyond sex-differences in overall brain size; show a consistent spatial patterning (r ~ 0.8) within and across samples; are small-medium in absolute effect size; and, include regions implicated in multiple psychiatric disorders. Single nucleus RNAseq at hotspots of sex-biased brain volume find similar cellular proportions in males and females (p > 0.05) but extensive cell-type specific sex-differences in gene expression (FDR q < 0.05) that are most prominent for glial cells and enriched for genes implicated in diverse sex-biased psychiatric conditions.

Conclusions: This work nominates numerous anatomical and molecular brain systems that show sex-biased organization in humans—identifying potential pathways for sex-differences in psychiatric risk. These pathways represent empirically prioritized targets for sex-specific modulation of mental health outcomes.

Disclosure: Nothing to disclose.

53.3 Gonadal and chromosomal contributions to sex differences in mammalian brain organization

Jason Lerch

University of Oxford, Oxford, United Kingdom

Background: Sex differences in brain development may contribute to well-known sex differences in behavior and neuropsychiatric risk - making it important to comprehensively map and mechanistically annotate normative sex differences in brain organization. Most sex differences in brain development have previously been attributed to differential effects of gonadal hormones based on the observed effects of rodent endocrine manipulations on canonical subcortical foci of male-biased brain volume. However, we have so far lacked a systematic test for the relative contribution of gonadal vs. sex chromosome effects across all regions of sex-biased brain volume.

Methods: We used structural neuroimaging scans from wild-type (n = 670) and transgenic mice, alongside automated image processing and advanced statistical analyses, to dissociate gonadal and sex chromosome dosage (SCD) effects (n = 181). We complement this with targeted single nucleus RNA sequencing within a region of female-biased cerebellar volume.

Results: We show that: (i) many more regions of the murine brain are volumetrically sex-biased than previously recognized, and (ii) these often arise through a combination of both gonadal and SCD effects. Although gonadal effects dominate, SCD effects are: widespread; particularly influential in female-biased regions; and, more reflective of X- rather than Y-chromosome dosage effects. snRNA-seq reveals that combined gonadal and SCD effects also shape sex-biased gene expression.

Conclusions: These findings revise our understanding of the anatomical distribution and causal basis for sex-biased mammalian brain development - thereby illuminating an important axis of neuroanatomical variation in health and disease.

Disclosure: Nothing to disclose.

53.4 Gene regulation by steroid hormone receptors defines sex differences in the mouse brain

Jessica Tollkuhn

Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States

Background: Sex is a primary contributor to the incidence and etiology of mental health disorders however the underlying mechanisms that drive sex differences in disease risk and resilience remain largely unknown. Decades of research in animal models have shown that sex steroid hormones are the principal modulators of sex differences in brain development and function. These hormones primarily act through their cognate nuclear receptors, which are transcription factors. Our research identifies the genomic targets of sex hormone receptors in the brain and explores how such targets modulate neuronal physiology, circuit connectivity, and behavior.

Methods: This talk will present ongoing studies that assess gene expression and chromatin accessibility in neurons that express estrogen receptor alpha (ERα). We enrich for the most sex-variable populations of neurons in the brain via a published genetic labeling and nuclear sorting strategy. To identify emerging sex differences in chromatin accessibility in the maturing C57BL/6 mouse brain, we performed ATAC-seq in ERα neurons from three brain regions before (postnatal day 28), during (P35), and after (P50) the onset of puberty. 3 biological replicates of 50K nuclei pooled from 3–5 animals were taken for each sample.

Results: We find minimal sex differences at P28, and robust emergence of sex differences from P35 into P50. We observe that emerging sex differences in chromatin accessibility are largely defined by testosterone. The most significantly sex-variable chromatin regions (ANOVA-like generalized linear model, FDR < 0.001) exhibit several trajectories by k-means clustering. Male-biased chromatin accessibility is driven primarily by androgen receptor (AR) genomic binding and is augmented by ERα genomic binding. Female-biased chromatin accessibility is predominantly associated with activity-dependent signaling, not signaling through ovarian hormones.

Conclusions: Our findings reveal a comprehensive list of AR-regulated genes in the brain and additionally show that a significant component of male-biased gene expression is driven by ERα, likely due to continued aromatization of testosterone into estradiol in the adult brain. We anticipate that these candidate genes contribute to unique neurophysiological states in males that underlie resilience or susceptibility to mental health disorders.

Disclosure: Nothing to disclose.

Panel

54. Cerebellar Circuits in the Pathophysiology of Neuropsychiatric Disease in Humans and Rodents

54.1 Cerebellar control during supra second time estimation

Krystal Parker

University of Iowa, Iowa City, Iowa, United States

Background: A myriad of neuropsychiatric disorders involve cognitive dysfunction, yet the role of the cerebellum remains unknown. There are no current treatments that target cognitive dysfunction such as working memory, attention, and timing. We define the neural mechanisms for how cerebellar activity is relayed to the thalamus, what thalamic computations/integrations are necessary, and how the circuit defines frontal activity and cognitive function.

Methods: Interval timing relies on cognitive processes such as working memory and attention and is known to be abnormal in schizophrenia. Rats are trained to associate stimuli (light/tone) with temporal durations (4 and 12s) for water rewards. We recorded neural activity in the lateral cerebellar nuclei, medial dorsal thalamic nuclei, and medial frontal cortex in rats well trained in the interval timing task using a tetrode hyperdrive. We present data from 6 rats – 862 neurons from the medial frontal cortex, 1545 medial dorsal thalamus nuclei, and 800 lateral cerebellar nuclei neurons. Data are analyzed for modulation around the cue and reward and for ramping or increasing or decreasing activity over the interval. Further, we divide trials into adaptively timed, mistimed, and non-response trials to define the functional significance of this activity in temporal processing. Analyses will also define how cerebellar modulation of thalamic and frontal neurons using more advanced neurophysiological analyses including spike-spike and spike-field coherence.

Results: Preliminary analyses identified neurons in the lateral cerebellar nuclei that are inhibited in a ramping down pattern to the time of the trained interval. Single neurons maintained the nadir (lowest point) of their activity to the time of the trained interval with altered slopes to the specific interval on adaptively timed trials. This pattern of activity was less precise on mistimed trials, and neurons were not modulated on non-response trials.

Conclusions: The cerebellum is necessary to precisely encode supra second temporal durations in the interval timing task given neuronal timing precision was only present on adaptively timed trials. How this inhibitory cerebellar output influences downstream timing circuitry is unknown but we define this relationship and shed light on the role of the cerebellum in timing in the range of seconds to minutes.

Disclosure: Nothing to disclose.

54.2 Cerebellar functional connectivity across the lifespan: age-normative models and their implications in psychosis

Hengyi Cao

Feinstein Institute for Medical Research, Queens, New York, United States

Background: Cerebellar dysconnectivity is strongly implicated in neuropsychiatric disorders including psychosis. To better understand its mechanisms, it is essential to build lifespan charts of cerebellar connectivity. Such charts would serve as valuable references for evaluating age-standardized cerebellar “normality” at the individual level and its clinical relevance.

Methods: We analyzed resting-state fMRI data from 2330 healthy individuals (aged 6–100 years) across three large-scale Human Connectome Project (HCP) cohorts—HCP Development (601 subjects), HCP Young adult (1011 subjects), and HCP Aging (718 subjects). Cerebellar connectivity was computed for ten cerebellar functional systems defined by the CAB-NP atlas. We used the Generalized Additive Model for Location, Scale and Shape (GAMLSS) to estimate connectivity changes for each cerebellar system across the lifespan, separately by sex. The resulting age-normative models were further applied in an independent clinical dataset of early psychosis (HCP-EP, 115 patients and 49 healthy controls, aged 16–36 years). Z scores quantifying connectivity deviations from the age-normative models were calculated for each individual and were compared between groups.

Results: All ten cerebellar systems showed significant age-related effects (p < 0.001). Progressively declined cerebellar connectivity was observed across the lifespan in both males and females. On top of this, males showed relatively stable connectivity in the sensory systems and slightly increased connectivity in cognitive systems (language and frontoparietal) after midlife, while females showed relatively stable connectivity in these cognitive systems after midlife. In patients, significantly lower z scores (more negative deviations) were observed, in particular the primary visual (p = 0.03), secondary visual (p = 0.005), sensorimotor (p < 0.001), default-mode (p = 0.002), cingulo-opercular (p = 0.02), attention (p = 0.02), and multimodal integration (p = 0.01) systems.

Conclusions: This is the first study to establish age-normative models of cerebellar connectivity across the lifespan. The results suggest progressive segregation of cerebellar systems with age. Moreover, greater negative deviations in psychosis also align with the “synaptic over-pruning” and “accelerated aging” hypotheses of schizophrenia.

Disclosure: Nothing to disclose.

54.3 Dynamic changes in norepinephrine and dopamine levels in the cerebellum for adaptive cognition

Erik Carlson

University of Washington, Seattle, Washington, United States

Background: The locus coeruleus (LC), the brain’s primary source of noradrenaline, plays a crucial role in arousal, attention, and cognitive flexibility. Dysregulated LC function is linked to psychiatric and neurodegenerative disorders. While its projections to cortical and limbic areas are well studied, recent evidence highlights a distinct LC population targeting the cerebellum, a region increasingly associated with cognition. However, the functional significance of LC-cerebellar signaling remains unclear.

The dentate nucleus (DN), the primary cerebellar output for cognition, integrates sensory cues with internal models predicting expected outcomes, adapting behavior through continuous updating based on salience and novelty. We hypothesized that LC activation modulates DN circuits, identified by their expression of the dopamine D1 receptor (DND1R), to incorporate salient events and guide behavioral adaptation.

Methods: Using fiber photometry (FP) with virally delivered biosensors (GRAB-NE1m, GRAB-DA3m, GFP control), we measured DN dopamine and norepinephrine activity during operant delayed alternation and reversal tasks (N = 5/group). We assessed the necessity and sufficiency of LC projections to DN and catecholamine-receptive DND1R neurons using opto- and chemo-genetics (N = 10/group). Circuit mapping and translational profiling further characterized DND1R neurons.

Results: Our data reveal dynamic dopamine signals in the DN during key cognitive task periods, including post-lever press and reward reservoir entry. Successful task execution resulted in transient increase in phasic GRAB-DA activation in DN, followed by reduced tonic GRAB-DA activation compared to unsuccessful responses (95% CI). Manipulating DND1R neuron activity influenced task performance, with inhibition impairing and excitation improving outcomes (P < 0.05, 2-way repeated measures ANOVA for group and interaction of group and training).

Conclusions: These results support the role of DN catecholamine activity in adaptive cognitive flexibility. The data points towards a novel cerebellar computational unit driving cognitive flexibility, and clarifies LC’s neuromodulatory role in shaping cerebellar function.

Disclosure: Nothing to disclose.

54.4 Cerebellar modulation of cortical networks during task and rest

Catherine Stoodley

Children's National Medical Center, Washington, District of Columbia, United States

Background: The cerebellum is thought to build internal models that allow for the feedforward optimization and flexible adaptation of a wide range of behaviors. It has been proposed that the cerebellum exerts its influence through recruiting and integrating cerebral cortical networks in a task-specific manner. This has been shown in preclinical models using electrophysiology, where a primary cerebellar manipulation alters the functional coherence of cortico-cortical networks without disrupting within-region local field potentials.

Methods: We investigated this concept using a combination of non-invasive neuromodulation, functional MRI, and behavioral measures. Transcranial direct current stimulation (tDCS; 20min of 1.5mA) was used to modulate different cerebellar subregions (posterior midline, right lateral hemisphere) in n = 33 neurotypical young adults. Each participant completed three fMRI sessions with anodal (excitatory), cathodal (inhibitory) and sham tDCS. Post-tDCS fMRI data were acquired during a cognitive flexibility task and during rest. The CONN Toolbox was used to assess functional connectivity changes after cerebellar tDCS at rest (multivariate pattern analysis [MVPA]) and during the task (gPPI). Linear mixed effects models were used to evaluate the impact of cerebellar tDCS on cognitive flexibility.

Results: MVPA analyses (voxel p < 0.005, FDR cluster corrected p < 0.01) revealed that tDCS targeting the midline cerebellum altered functional connectivity in the default mode network; modulation of the right lateral cerebellum impacted functional connectivity of fronto-parietal and attention networks. The cognitive flexibility task robustly engaged the cerebellum (voxel FWE p < 0.05, cluster FDR p < 0.05) when the flexibility trials were compared with control trials. Preliminary analyses indicate that cerebellar tDCS did not significantly impact task performance. We are currently evaluating how tDCS alters task-based connectivity patterns.

Conclusions: These findings support the idea that the cerebellum organizes the functional connectivity of cerebral cortical networks. We suggest that the lateral cerebellum shifts the cerebral cortex into a task-ready state and that the cerebellum contributes to the flexible adaptation of behavior, consistent with theoretical models of cerebellar function.

Disclosure: Nothing to disclose.

Panel

55. Assessing and Targeting Sleep Oscillations to Improve Outcomes in Neuropsychiatric Disorders

55.1 Abnormal sleep and wake neurophysiology in adolescents with autism spectrum disorder

Dara Manoach

Massachusetts General Hospital, Charlestown, Massachusetts, United States

Background: Sleep disturbances affect ~80% of children with ASD and impair daytime function. Converging evidence suggests dysregulated thalamocortical communication (TCC) as a key contributor. During sleep, the thalamus generates spindles to prevent arousals, and during wake, reduced thalamic gating of sensory relay may increase sensory sensitivity. We recently reported reduced sleep spindles that correlated with disturbed sleep in adolescent boys with ASD (Mylonas et al., 2022). I will present the results of an ongoing study that replicates these findings and investigates whether dysregulated TCC also contributes to waking manifestations of ASD.

Methods: We acquired 3 nights of sleep data at home using wearable EEG devices in 71 adolescents with ASD (age: 15+/−2; 24 F) and 38 of their typically developing peers (TD; 15+/−2; 22 F). A subset of 23 ASD and 12 TD subjects also had sensory gating ERPs. Sleep staging, artifact rejection, and oscillation detection were completed with open source algorithms. We regressed stage 2 spindle density against sleep quality, ERPs, and sensory sensitivity ratings.

Results: ASD subjects had worse sleep quality than TD (wake after sleep onset: WASO: F(1,105) = 9.06, p = 0.0030; Sleep Fragmentation Index: SFI: F(1,105) = 8.38, p = 0.005). A Group by Sex interaction (F(1,105) = 3.96, p = 0.049) reflected that ASD males had lower spindle density than both TD males (t(61) = −2.04, p = 0.046) and ASD females (t(69) = 2.71, p = 0.008). ASD and TD females did not differ (p = 0.38) and there was no sex difference in the TD group (p = 0.72). Regardless of sex or group, lower spindle density predicted more WASO (r = −0.20, p = 0.049) and higher SFI (r = −0.26, p = 0.006). There were no group differences in sensory gating, nor did it correlate with spindle density or sensory sensitivities, but a larger sample is needed.

Conclusions: We replicated findings of reduced spindle density in adolescent boys with ASD and of worse sleep quality in both sexes. Findings of increased spindle density during high estrogen phases of the menstrual/estrus cycle suggest that estrogen affects TCC and may have protective effects in females with ASD. Given that spindles protect sleep, the correlations of spindle deficits with worse sleep quality suggest spindles as a treatment target. Our findings of abnormal sleep physiology in ASD are consistent with other evidence implicating dysregulated TCC.

Disclosure: Novartis, Consultant, Self

55.2 Sleep oscillatory deficits in psychosis risk and early course schizophrenia: a target engagement biomarker?

Fabio Ferrarelli

University of Pittsburgh, Pittsburgh, Pennsylvania, United States

Background: In Schizophrenia (SCZ), early interventions can make a difference, particularly for cognitive dysfunction. In healthy subjects (HS), cognitive performance is associated with sleep-specific oscillations- spindles and slow waves. In recent work we demonstrated reduced spindles and slow waves in SCZ using high-density (N ≥ 64 channels) EEG recordings. However, it remains to be established: 1) if sleep oscillatory and cognitive deficits are both present and easily measurable in early course patients (EC-SCZ) vs. HS; and 2) if sleep manipulation with closed loop auditory stimulation (CLAS) can improve these deficits in EC-SCZ patients.

Methods: We collected single channel EEG with simultaneous PSG and the motor sequence tapping (MST) and the AX-Continuous Performance Task (AX-CPT) before and after sleep in EC-SCZ and HS groups. EC-SCZ patients also underwent CLAS and sham nights in a double-blind, cross-over design with sleep oscillations, MST, and AX-CPT assessments. Spindle duration, density, integrated spindle activity (ISA) and slow wave density and changes in overnight performance and reaction time (RT) were assessed.

Results: Baseline EEG/PSG and cognitive assessments were collected in N = 30 EC-SCZ (F = 11, M ± SD = 24.3 ± 4.7) and N = 30 HS (F = 12, M ± SD = 24.4 ± 4.8). Compared to HS, EC-SCZ patients had reduced spindle duration (0.83 ± 0.14 vs. 0.96 ± 0.18, T = 2.9, p = 0.005), density (1.89 ± 0.64 vs. 2.37 ± 0.57, T = 3.7, p = 0.0004), ISA (8.08 ± 5.23 vs. 11.45 ± 5.73, T = 3.83, p = 0.0003), and slow wave density (35.29 ± 3.35 vs. 36.48 ± 5.73, T = 3.26, p = 0.002). Furthermore, HS, but not EC-SCZ patients, showed improvement in overnight MST performance (T = 2.50, p = 0.018) and RT in the AX-CPT task (T = −2.62, p = 0.014). EC-SCZ patients (N = 28) also completed CLAS and sham nights and repeated measure ANOVAs found night effect for spindle density (F = 5.42, p = 0.007) and ISA (F = 3.37, p = 0.04), with one stimulation night with higher values vs. baseline and the other stimulation night.

Conclusions: Combined, these findings indicate that sleep spindle and slow wave deficits alongside cognitive impairments are present in EC-SCZ patients, and that sleep oscillatory deficits can be detected with a wearable single EEG channel device. We also show that CLAS is feasible in EC-SCZ and provide initial evidence that improvement of sleep oscillatory deficits is possible in those patients.

Disclosure: Nothing to disclose.

55.3 Local sleep electroencephalography biomarkers of inflammation and Alzheimer’s disease-related pathophysiology

Bryce Mander

University of California, Irvine, Irvine, California, United States

Background: Alzheimer’s disease (AD) pathophysiology is associated with sleep deficits, but their biological sources remain unclear. Here, we used spectral parameterization in high density electroencephalography (hdEEG) data recorded alongside overnight polysomnography (PSG) to characterize relationships among cerebrospinal fluid (CSF) AD biomarkers and periodic and aperiodic sleep EEG signals affiliated with oscillatory activity (exponent corrected power), excitatory/inhibitory [E/I] balance (exponent slope), background spiking activity (aperiodic offset), and neuronal timescales (knee frequency).

Methods: Cognitively unimpaired older adults (61.4 ± 6.3 years, 38/58 female) underwent PSG with hdEEG and CSF sampling after an overnight fast. EEG data during non-rapid eye movement (NREM) and REM sleep were preprocessed and multitaper [11 tapers] spectral analysis was implemented. Spectral parameterization was then used to compute aperiodic and periodic estimates. Analyses focused on AD-related proteins (Aβ40, Aβ42, total tau, phosphorylated tau), inflammation (GFAP, S100β, YKL-40, soluble TREM2), and synaptic integrity (neurogranin, neurofilament light chain protein, alpha-synuclein) which were quantified using the NeuroToolKit.

Results: Higher S100β was associated with lower centro-temporal NREM slow wave activity and fronto-temporal REM beta and higher centro-temporal NREM theta and frontal beta. S100β was also associated with a shallower centro-temporal NREM exponent slope, a lower parietal REM aperiodic offset, and a lower knee frequency. Higher GFAP was associated with lower fronto-parietal REM theta and central NREM aperiodic offset, while higher YKL-40 was associated with lower frontal sigma and higher soluble TREM2 was associated with lower fronto-temporal REM beta. AD-related proteins were associated with lower frontal NREM sigma, fronto-temporal REM theta, and parieto-temporal REM beta and higher frontal NREM theta and centro-temporal NREM alpha. Lower synaptic integrity was associated with lower NREM sigma and NREM and REM beta and higher NREM theta and NREM and REM alpha.

Conclusions: AD biomarkers are associated with local deficits in aperiodic and oscillatory sleep features, supporting the importance of isolating aperiodic and periodic EEG features from sleep data for biomarker discovery.

Disclosure: Astronautx, ltd., Advisory Board, Self

55.4 Metabolic modulation of sleep oscillations as a therapeutic approach in Alzheimer’s disease

Caitlin Carroll

Wake Forest University, School of Medicine, Winston Salem, North Carolina, United States

Background: Metabolic impairment and sleep disruption are both modifiable risk factors in the development of Alzheimer’s disease (AD). Further, they seem to have bidirectional relationships with AD, where they are both a cause and consequence of pathology. Sleep disturbances also increase risk for metabolic syndrome, however, it is unclear if the inverse relationship exists, where peripheral metabolic impairment disrupts sleep. Further, little is known about how these risk factors interact across AD pathogenesis and how lifestyle interventions impact these relationships.

Methods: We first established the dynamic interplay of sleep and metabolism as a function of age and pathology. To do this, we implanted biosensors measuring interstitial fluid (ISF) levels of glucose and lactate directly into the hippocampus of wildtype and APP/PS1 mice, a model of amyloid-beta (Aβ) overexpression, at 3-, 6-, and 9-months of age (n = 5–8/group). Biosensors were paired with cortical EEG and EMG recordings for simultaneous sleep analysis. We also evaluated whole-body peripheral metabolism using glucose tolerance tests and indirect calorimetry. We then investigated the effect of an acute metabolic treatment on sleep and metabolic function in 6 month old APP/PS1 mice using metformin (1.8mg/mL in drinking water for 7 days; n = 6–7/group).

Results: We found that Aβ accumulation decreased NREM sleep time (p < 0.001) and delta power (p < 0.01). Decreased NREM slow wave sleep was associated with the loss of ISF lactate diurnal rhythms (p < 0.001), reflecting altered neuronal activity dynamics across the 24-hour period. We also found that Aβ pathology was sufficient to disrupt peripheral metabolic function (p < 0.01). Importantly, we were able to normalize the deficits by targeting peripheral metabolism. Metformin treatment increased NREM sleep (p < 0.05) and relative delta power (p < 0.01) and normalized ISF lactate dynamics (p < 0.001), independent of changes in amyloid plaque load.

Conclusions: We found Aβ accumulation was sufficient to disrupt NREM slow wave sleep, ISF lactate dynamics, and peripheral metabolic function. We also showed that metformin treatment normalized these disturbances, independent of pathology. Our findings highlight an important link between these AD risk factors, and identify metabolic impairment as a potential multifactorial target in AD treatment.

Disclosure: Nothing to disclose.

Panel

56. Leveraging Naturalistic Neuroimaging to Unravel Mechanisms of Psychiatric Illness

56.1 Mood induction during naturalistic movie viewing in participants with mood disorders and healthy volunteers in MEG

Elizabeth Ballard

National Institute of Mental Health, Bethesda, Maryland, United States

Background: Low mood and decreased response to positive events are key characteristics of depression. The use of “naturalistic” stimuli, such as film clips, provides an opportunity to evaluate brain synchronization in the context of mood changes. Advances in neuroimaging allow for in-depth evaluations of neural synchrony using inter-subject correlations (ISC), but few have evaluated the impact of mood induction paradigms in individuals with psychiatric diagnoses. This study examined a mood induction battery using movie clips in a sample of individuals with mood disorders and healthy volunteers during magnetoencephalography (MEG).

Methods: 42 participants with mood disorder diagnoses (MD, 20F/22M) and 30 healthy volunteers (HVs, 21F/9M) viewed two movie clips selected to elicit sadness (negative affect) and two movie clips to elicit tenderness (positive affect). Changes in mood after each clip was assessed with the Positive and Negative Affect Schedule (PANAS). MEG data were bandpass filtered into frequency bands (Alpha, Beta, Delta, High/Low Gamma, Theta) and Hilbert transformed. These processed data were then source modeled using Boundary Element Model forward solution with dSPM inverse operator in MNE-Python. Pairwise subject correlations were performed in source space using AFNI across all participants; ISC analysis used a Linear Mixed Effects model (3dISC) to identify group effects.

Results: MDs and HCs demonstrated clip-congruent mood reactivity in response to movie clips, suggesting that they became “sadder” after watching the sad movies (p < 0.05.). Source reconstructed brain responses show increased ISCs in HVs as compared to MDs in the sad films across frequency bands, including in the motor and visual cortices in theta, anterior cingulate cortex in alpha, and in the orbitofrontal cortex in beta. In comparison, there was relatively little divergence in ISCs in the positive film clips.

Conclusions: The naturalistic mood induction impacted negative mood in the expected direction. In response to this mood induction paradigm, we observed altered neural synchrony in individuals with MDs as compared to HVs, although primarily in response to the negative film clips. This approach takes advantage of the temporal resolution afforded by MEG, which may be uniquely positioned to capture neural synchrony in response to naturalistic stimuli.

Disclosure: Nothing to disclose.

56.2 Disruption of social inference pathways in schizophrenia

Gaurav Patel

Columbia University, New York, New York, United States

Background: Making inferences about people’s thoughts and feelings requires quick integration of complex dynamic sensory information with ongoing theory-of-mind (ToM) operations. The temporoparietal junction (TPJ) and superior temporal sulcus (STS) contain areas relevant to face-emotion recognition, speech, visual attention, and ToM. Here we detail how these areas form the basis of three TPJ-STS social inference pathways, relate them to social cues, and show how they are disrupted in schizophrenia (Sz).

Methods: We collected BOLD-fMRI data from participants watching a 12-minute audio/visual movie clip (22 healthy controls (HC), 22 Sz participants (SzP)) or a 15-minute visual-only movie clip (23 SzP, 20 HC). We clustered (k-means) the resulting BOLD time-courses into co-activation pattern (CAP) states, examined their association with movie features, and examined which features were present when SzP and HC CAP states diverged.

Results: We found three TPJ-STS CAP states associated with social cues (pFDR < 0.05). The first CAP state included visual, TPJ attention, pSTS face-emotion, and STS ToM areas; corresponded to visual motion, face motion, and saccades; and SzP divergence was associated with visual motion and socialness. The second CAP state included auditory, STG language, and TPJ/STS ToM areas; corresponded with faces, speech, and socialness; and SzP divergence was associated with all of these, especially positively valenced speech. The third CAP state included late visual, STG language, pSTS face-emotion, and TPJ/STS ToM areas; corresponded to faces, face motion, speech expressions of ambiguous emotion, and socialness; and SzP divergence was associated with faces and speech expressions of ambiguous emotion, with the strongest effects for sarcasm.

Conclusions: These results support the existence of three overlapping but distinct TPJ-STS pathways for social inference—one for visual scanning of facial expressions, another for speech processing, and another for integration of facial expressions and speech. SzP demonstrate abnormalities in activation of all three pathways, particularly for ambiguously and positively valenced speech. These findings suggest that disruptions of TPJ-STS pathways affects processing of visual and speech features important for making social inferences with downstream consequences on social functioning.

Disclosure: Nothing to disclose.

56.3 Individual differences in emotion-selective encoding and pediatric anxiety and depression

M. Catalina Camacho

Washington University in St. Louis, St. Louis, Missouri, United States

Background: Emotion cues are learned in context—linked to cause and consequence—in early childhood. Depression and anxiety each are associated with differences in emotion processing, however the link between symptoms and neural encoding of emotions in context is not yet fully elucidated. The goal of this study is to use movie-watching fMRI to identify 1) how specific emotions are selectively encoded in the cortex with full semantic and low-level context included in the model; and 2) examine individual differences in emotion selectivity encoding in relation to self-reported depression and anxiety symptoms.

Methods: Functional MRI data obtained while watching an emotionally evocative video clip from a total of 537 youth (ages 5–15 years) from the Healthy Brain Network Biobank study were used for analysis. Participant-level elastic net regression encoding models were applied to estimate vertex-level encoding selectivity. Models included emotion (e.g., anger, fear, happy), semantic (e.g., faces, spoken language), and low-level (e.g., brightness, loudness) video features. Support vector regression models were next used to test if there was a multivariate association between emotion selectivity encoding and self-reported anxiety (Screen for Child Anxiety Related Disorders) and depression (Mood and Feelings Questionnaire) symptoms.

Results: Individual differences in encoding sad emotions from fear were associated with total depression scores (model fit ps < 0.05). Greater difference in encoding sad from fear in the somatomotor and cingulo-opercular regions and lower difference in encoding in fronto-parietal regions were associated with each greater depression and anxiety (rs > 0.1). There were no associations with non-emotion video features.

Conclusions: This work suggests that how youth encode naturalistic sad versus fearful content in specific cognitive networks differ as a function of symptoms, giving insight to real-world processing. Next, we plan to further characterize these associations by examining individual differences in the spatial extents of emotion encoding in the cortex as well as associations with specific symptom domains.

Disclosure: Nothing to disclose.

56.4 Leveraging natural language processing to link subjective experience of emotions to brain function in pediatric anxiety

Peter Kirk

National Institute of Mental Health, Bethesda, Maryland, United States

Background: Research on anxiety focuses on behaviors and physiological responses which may be underpinned by activity in amygdala, insula, and cingulate cortex. Whether these circuits also instantiate subjective experiences of anxiety is unclear, a major challenge for clinical neuroscience.

Methods: We presented a semi-naturalistic, anxiogenic movie during fMRI in a pediatric sample with and without anxiety disorders (N = 84). Participants responded to a set of interview questions about the movie. We quantified content and valence of interview data via natural language processing. These measures were linked to brain activity patterns via intersubject correlations.

Results: Preregistered analyses found wide-spread brain activity during the movie—including in anterior insula cortex and the dorsal attention network—correlated with participant’s descriptions of the movie’s narrative (p = 0.0012). Secondary analyses also revealed interactions between anxiety, age, and the valence of verbal appraisals (p = 0.014).

Conclusions: Our primary analyses link movie-evoked brain activity and subsequent interview content in a pediatric sample. The language participants used when recalling anxiogenic movie content robustly indexed brain activity. Secondary analyses suggested older but not younger patients with anxiety demonstrate more negative appraisals of the anxiogenic experience. Our findings highlight a promising avenue for neuroscience research on subjective emotional experiences in anxiety.

Disclosure: Nothing to disclose.

Panel

57. Using Computational Models to Dissect Symptom Heterogeneity Across Conditions, Constructs, and Contexts

57.1 Sacrificing quality of life to avoid feared outcomes: the relationship between maladaptive avoidance, anxiety, and subjective well-being

Ryan Smith

Laureate Institute for Brain Research, Tulsa, Oklahoma, United States

Background: Maladaptive avoidance (MA) is a key maintenance factor in affective disorders, causing significant decreases in well-being. Reduced exploration within explore-exploit tasks represents one means of modeling MA. Yet, existing tasks tend to focus on monetary gains/losses as opposed to affective stimuli. They are also not optimized to capture the fact that MA involves sacrificing quality of life to avoid feared outcomes – instead settling for suboptimal but safe outcomes (e.g., remaining at home in agoraphobia).

Methods: Here we tested an affective 3-armed bandit task with positive, negative, and neutral outcomes to better capture this structure in an online sample (N = 563 after task exclusion criteria). A space of 8 nested reinforcement learning models and 8 nested active inference models was fit to the data and subjected to Bayesian model comparison. Separate item-wise exploratory factor analyses were used to extract dimensions across a set of anxiety and well-being measures. Canonical correlation analyses (CCA) were used to examine whether affective factors showed relationships with model parameters.

Results: CCA results included two significant canonical modes (ps < .001, r2 = 23.33% and 11.70%). Loadings indicated anxiety sensitivity, life satisfaction, and purpose in life were related to the following parameters in the winning model: greater decision noise, less optimism, greater forgetting rate, and slower learning rate for negative outcomes. The opposite pattern was related to self-reported personal growth. Female individuals and those with panic and agoraphobia showed lower reward motivation, greater forgetting rate, and faster learning for negative and neutral outcomes.

Conclusions: Those with panic and agoraphobia symptoms avoided negative outcomes at the expense of positive outcomes – explained by lower reward motivation, greater recency bias, and faster learning from both neutral and negative outcomes. Unexpectedly, greater decision noise, less optimism, and suboptimal learning were independently linked to higher well-being, suggesting distinct affective influences. However, the opposite pattern was observed for those with greater self-reported personal growth, suggesting greater directed exploration and better task performance. These Results: support this task as a novel probe of maladaptive avoidance.

Disclosure: Nothing to disclose.

57.2 Neurocomputational mechanisms of self-referential processing in psychosis: formalizing brain-behavior connections to predict symptom expression

Carly Lasagna

University of Michigan, Ann Arbor, Michigan, United States

Background: Individuals with psychosis (SZ) show difficulties judging whether social cues, like eye contact, are self-directed, which may contribute to referential and persecutory delusions. Previous work has focused on prior beliefs as potential drivers, but recent computational modeling data have highlighted fundamental disruptions in how social information is dynamically processed (“evidence accumulation”). This is a novel mechanism capable of bridging neural dysfunction and symptom heterogeneity, demanding further empirical testing.

Methods: First, referential gaze perception performance was modeled via Diffusion Decision Models (DDMs), within-diagnoses (39 SZ/42 controls [HC]; 51% female) and transdiagnostically (111 with psychosis/social anxiety/autism traits; 76% female). Symptoms captured by evidence accumulation were tested via regressions. Second, the dynamic correspondence between evidence accumulation and EEG activity was modeled via single-trial neurocognitive joint DDMs (28 SZ/34 HC; 34% female). We tested whether neural data alone or the overlap between neural and cognitive states best predicted delusions.

Results: Less efficient evidence accumulation predicted more delusions in SZ (β = −.36 [−.64, −.1]), and more psychosis traits (β = −.24 [−.4, −.07]) and social anxiety (β = −.23 [−.4, −.08]), but not autism. Delusion severity in SZ was best predicted by trial-level coordination between midfrontal theta and evidence accumulation (β = −.39 [−.62, −.14]), not task-averaged theta alone.

Conclusions: Impaired evidence accumulation during self-referential social processing captured clinical/subclinical psychosis and social anxiety symptoms, dimensions marked by social fears/suspicions. In SZ, the dynamic interplay between neural and cognitive states, not task-averaged neural activity alone, predicted delusions, underscoring the clinical utility of model-based approaches. Attenuated neural synchronization to social information in SZ may signal top-down dysregulation with relevance to the development of delusions.

Disclosure: Nothing to disclose.

57.3 Gamified behavioral and computational markers of latent psychopathology enhance suicide‑risk prediction

Andreea Diaconescu

Centre for Addiction and Mental Health, University of Toronto, Toronto, Canada

Background: Suicide is the third leading cause of mortality among 15–29‑year‑olds, yet existing clinical predictors offer only modest precision. Deficits in social cognition and response inhibition map onto HiTOP spectra—Distress, Disinhibition, and Detachment—suggesting targets for computational phenotyping. We tested whether two gamified tasks assessing social inference (Jungle Treasure Hunt) and approach avoidance Go/No Go (Space Explorer) yield reliable behavioural and computational markers of these spectra and improve prediction of suicide capability.

Methods: Adults with mental health concerns (N = 237) completed both games plus HiTOP, Capability for Suicide (GCSQ) and Interpersonal Needs (INQ) scales at baseline and two-week retest. Space Explorer yielded three continuous indices—mean reaction time, Pavlovian approach–avoidance bias, and win‑stay/lose‑switch propensity, while Jungle Treasure Hunt provided phase‑specific accuracy, advice‑taking propensity, and wager magnitude. Trial‑level reaction times and choices were modelled with a reinforcement‑learning drift–diffusion model for Space Explorer and a Hierarchical Gaussian Filter for the Jungle Treasure Hunt game. Test-retest reliability used intraclass correlations (ICC). Bootstrapped structural equation models (SEM) linked game metrics to latent HiTOP factors, and hierarchical regressions tested incremental prediction of fearlessness of death.

Results: Continuous game metrics were moderately reliable (ICC ≤ 0.65), while categorical accuracy was poor (ICC ≤ 0.4). HiTOP spectra were highly stable (ICC ≥ 0.75). SEM showed Space Explorer behaviour loaded chiefly on Disinhibition, with Detachment secondary; escape bias flipped from positive to negative as suicidality rose among high antagonism participants. Jungle Treasure Hunt accuracy inversely predicted fearlessness of death both at baseline (β = –20.9, p = 0.018) and retest (β = –23.7, p = 0.006), with stronger effects at higher HiTOP suicidality.

Conclusions: Gamified tasks provide robust, HiTOP-aligned computational markers that enhance suicide risk stratification beyond self-reports. Their scalability supports integration into digital assessments and mechanism based prevention strategies.

Disclosure: Nothing to disclose.

57.4 Escaping or engaging: dissecting adaptive effort, control, and avoidance within a unified computational game platform for precision phenotyping

Nadja Ging-Jehli

Brown University, Providence, Rhode Island, United States

Background: Attention-deficit hyperactivity disorder (ADHD), depression, and anxiety co-occur and involve context-sensitive patterns of avoidance, effort, and outcome controllability. These constructs are typically studied in isolation, obscuring mechanistic interplays. Gearshift Fellowship (GF), a next-generation modeling-ready game platform, captures individual adaptation strategies across cognitive and social contexts. We used GF to probe how adaptive avoidance maps onto psychiatric symptoms and learning strategies across contexts.

Methods: Sixty adults (ages 18–40; 30 with self-reported ADHD) completed GF via Prolific, along with validated questionnaires measuring ADHD, depression, anxiety, and intolerance of uncertainty (IUS). Participants repeatedly chose between two options: escape (no effort, uncontrollable outcomes) or non-escape (controllable effort-based outcomes). A 2x2 design manipulated gain/loss framing and risk source (performance-based vs random), probing effort sensitivity, controllability, and adaptive avoidance. Choice patterns, response times were analyzed using linear mixed models, with follow-up diffusion decision modeling (DDM) to characterize latent dynamics.

Results: Higher IUS and ADHD scores predicted reduced escape under loss framing but only when non-escape offered higher reward. This reflects context-sensitive control preferences shaped by effort-reward trade-offs. Depression predicted reduced escape under loss framing regardless of reward, suggesting control is valued over effort cost. Anxiety predicted reduced escape under gain framing, even when escape was more rewarding, reflecting rigid, effort-insensitive control preferences.

Conclusions: These findings challenge trait-level views of effort avoidance, revealing distinct, context-sensitive control strategies across symptom profiles. GF provides a novel platform to model these mechanisms through naturalistic gameplay, offering new targets for symptom-specific interventions focused on effort engagement and control valuation.

Disclosure: Nothing to disclose.