When shorter lasts longer: Rapid induction of configural memory in Lymnaea stagnalis

Configural learning in the freshwater pond snail Lymnaea stagnalis is a well-established model for investigating higher-order associative learning. When snails simultaneously experience an appetitive food cue and predator cue, they form a configural association in which the food cue no longer elicits its normal feeding response but instead elicits a fear-associated suppression of feeding. The established conditioning procedure uses 45 min of simultaneous exposure to food and predator cue and produces a configural memory expressed 3 h after conditioning but not 24 h later. Here, we report the serendipitous discovery of a substantially shorter conditioning procedure that produces a more persistent memory. During experiments using carrot slurry (food cue) and crayfish effluent (predatory cue), individual snails were simultaneously exposed to the two cues for only 7 min. Unexpectedly, animals conditioned using this procedure showed suppressed feeding not only 3 h later but also at 24 h, demonstrating long-term configural memory. We therefore characterized the specificity and robustness of the 7-min procedure. Exposure to carrot slurry or crayfish effluent alone did not produce the persistent change in carrot-evoked feeding, demonstrating that the effect required the combined presentation of both cues. We also tested this using fish-conditioned water and shell clipping, which mimics predator attack and gave rise to the same results. Thus, a rapid 7-min conditioning procedure reliably induces long-term configural memory across chemically and physically distinct forms of predator-risk information. These findings establish a rapid and broadly applicable procedure for inducing long-term configural memory in L. stagnalis.