Fig. 2: Activity of DRN serotonin neurons modulates SRNs.

a, Mice were genetically manipulated to express ChR2 in DRN serotonin neurons before ofMRI experiments²⁹. b, Transcriptomic maps of serotonin receptor genes from the Allen Brain Institute. The combination of serotonin receptor maps and ofMRI via FSL DR allowed us to characterize SRNs. c, SRN time-courses of amplitude changes (DR-stage 1) during ofMRI. (Δ, changes from baseline activity; see Extended Data Fig. 2a). Top row shows SRN amplitude changes for control animals; bottom row for ChR2 animals. Each color represents an SRN; SRN colors are matched with the other panels. d, Time-locked ofMRI amplitude changes of SRNs (DR-stage 1) in control animals (left) and in ChR2 animals (right). Blue bar underneath represents when optogenetic stimulation was on. e, Results from permutation analysis of linear models testing differences between control and ChR2 animals on SRN time-locked responses. Statistical significance was assessed with 1,000 block-aware permutations, with FWE-corr for multiple comparisons across time, SRNs and two tails. Showing −log₁₀ FWE-corr P, corrected across time, SRNs and two tails. Dashed lines demarcate statistical thresholds. Together, panels d and e show a heterogeneity of SRN amplitude changes in response to optogenetic activation of DRN serotonin neurons. f, Results from permutation analysis of linear models testing differences between control and ChR2 groups on SRN functional connectivity maps (DR-stage 2). Statistical significance was assessed with 1,000 block-aware permutations, with FWE-corr for multiple comparisons across brain regions, SRNs and two tails. Showing −log₁₀ FWE-corr P, corrected across brain regions, SRNs and two tails. Cold colors represent decreased functional connectivity in the ChR2 group compared with the control group; hot colors represent increased functional connectivity. The results of this figure demonstrate that the spatial distribution of different serotonin receptor types confers functional specificity at the brain-wide level. CBV, erebral blood volume; TR, repetition time; vols, volumes.