Context extinction and associative learning in Lymnaea.

Aerial respiratory behavior in the pond snail Lymnaea was operantly conditioned so that snails learned not to perform aerial respiration in a hypoxic environment. Snails were trained in either the standard context (no food odorant) or a carrot (food-odorant) context. An operant training procedure of two 45-min training sessions with a 1-h interval between the sessions followed by a third 45-min training session 18 h later was sufficient to produce associative learning and long-term memory (LTM) that persisted for at least 5 days. If, however, following the third operant training session snails received three 45-min extinction training sessions, with each extinction session separated by at least a 1-h interval, LTM was not observed when tested the following day. That is, the memory was extinguished. Extinction, however, did not occur if the context of the extinction training was different from the context of the associative training. That is, in the snails trained in the standard context, extinction did not occur if the extinction training sessions were performed in the food-odorant context and vice versa.