A systems approach to the cellular analysis of associative learning in thepond snail Lymnaea

We show that appetitive and aversive conditioning can be analyzed at the ce llular level in the well-described neural circuitries underlying rhythmic f eeding and respiration in the pond snail, Lymnaea stagnalis. To relate elec trical changes directly to behavior, the snails were first trained and the neural changes recorded at multiple sites in reduced preparations made from the same animals. Changes in neural activity following conditioning could be recorded at the level of motoneurons, central pattern generator interneu rons and modulatory neurons. Of significant interest was recent work showin g that neural correlates of long-term memory could be recorded in the feedi ng network following single-trial appetitive chemical conditioning. Availab le information on the synaptic connectivity and transmitter content of iden tified neurons within the Lymnaea circuits will allow further work on the s ynaptic and molecular mechanisms of learning and memory.