Neuroscience of Memory Formation in Aquatic Gastropods

The study of memory formation in aquatic gastropods, chiefly the great pond snail Lymnaea stagnalis, has provided profound insights into fundamental mechanisms of learning. These molluscan models possess relatively simple central nervous systems composed of large, identifiable neurons, which facilitate precise mapping of cellular and synaptic events. Both classical and operant conditioning paradigms—such as conditioned taste aversion and aerial respiratory training—have been exploited to dissect the stages of memory acquisition, consolidation and recall. Research has revealed that long-term memory (LTM) in these animals depends on orchestrated changes in gene expression, neuromodulator release and circuit reconfiguration. Key molecular players include cyclic AMP‐responsive element binding proteins (CREBs), monoamines and insulin‐like peptides, all of which contribute to synaptic plasticity and network gating. At the circuit level, motifs of mutual inhibition, modulatory feedback and network oscillations have emerged as core motifs for state-dependent learning. Beyond basic neurobiology, gastropod studies inform broader questions of ageing, neurodegeneration and the impact of environmental stressors on cognition, and offer a tractable platform for screening compounds that modulate memory processes.

Research from Nature Portfolio

Recent studies have highlighted the molecular gating of LTM following a single conditioning trial. A specific microRNA, Lym-miR-137, is transiently up-regulated in key identified neurons and binds to the 3′ untranslated region of CREB2 mRNA, relieving a transcriptional brake on memory formation. Loss-of-function interventions demonstrated that without this microRNA-mediated down-regulation of CREB2, long-term associative memory fails to consolidate. Concurrent mapping of small non-coding RNA populations in the snail central nervous system has established a comprehensive profile of training-responsive regulators, laying the groundwork for future dissections of single-trial learning.

Neuroscience of Memory Formation in Aquatic Gastropods publication trend

The graph below shows the total number of articles in neuroscience of memory formation in aquatic gastropods across all publications each year (not limited to Nature Index journals).

Technical terms

Long-term memory (LTM): A phase of memory lasting hours to days, requiring new gene transcription and protein synthesis.

MicroRNA (miRNA): Small non-coding RNA molecules that post-transcriptionally regulate gene expression by binding to target mRNAs.

CREB2: A member of the cyclic AMP-responsive element binding protein family that acts as a transcriptional repressor of memory-related genes.

Conditioned taste aversion (CTA): An associative learning paradigm in which an organism learns to avoid a flavour following its pairing with an aversive stimulus.

Mutual inhibition motif: A circuit architecture in which two neurons or populations reciprocally inhibit one another, enabling bistable network states and gating of information flow.

Synaptic plasticity: The capacity of synaptic connections to strengthen or weaken over time in response to changes in activity, underlying learning and memory.

References

1. A circuit mechanism linking past and future learning through shifts in perception. Science Advances (2023).
2. LPS-Induced Garcia Effect and Its Pharmacological Regulation Mediated by Acetylsalicylic Acid: Behavioral and Transcriptional Evidence. Biology (2023).
3. The unlimited potential of the great pond snail, Lymnaea stagnalis. eLife (2020).
4. Monoamines, Insulin and the Roles They Play in Associative Learning in Pond Snails. Frontiers in Behavioral Neuroscience (2019).
5. Induction of LTM Following an Insulin Injection. eNeuro (2020).
6. A CREB2-targeting microRNA is required for long-term memory after single-trial learning. Scientific Reports (2018).
7. Learning-Dependent Gene Expression of CREB1 Isoforms in the Molluscan Brain. Frontiers in Behavioral Neuroscience (2010).