Classical Conditioning in Aplysia: Neuronal Circuits Involved in Associative Learning

Recent analyses of the neural control of learning and memory suggest that one needs to identify and examine the neuronal circuitry specific to the behavior that is modified by the learning in order to study the cellular mechanisms underlying these processes. In this paper we describe an example of a simple form of classical conditioning in the gastropod mollusk Aplysia californica. This example of associative learning offers considerable promise for a cellular analysis because it involves relatively simple and well-analyzed neuronal circuits. Knowledge of the neuronal circuits involved in the conditioning pathways is reviewed, and a preliminary hypothesis for the mechanisms of this form of classical conditioning is considered.