THE MISSING LINK BETWEEN NEUROBIOLOGY AND BEHAVIOR IN APLYSIA CONDITIONING

Over the past decades, a wealth of findings has led to a substantial c hange in the assumed complexity of classical conditioning. The combine d evidence indicates that temporal pairing is neither necessary nor su fficient for the formation of an associative connection. At the same t ime, studies of model invertebrate nervous systems have allowed us to ask a series of questions about the molecular basis of associative con ditioning, The discovery of a pairing-sensitive mechanism in the gill- withdrawal circuitry of Aplysia is regarded as the hallmark of the red uctionist approach. This review outlines the insights gathered from be havioral and neurobiological studies. Furthermore, the conceptual fram eworks guiding research at the 'what' and 'how' levels of analysis are compared and contrasted. I argue that a rich cognitive view of condit ioning has emerged at the 'what' level, whereas the traditional notion of temporal pairing still drives research at the 'how' level. A compl ete account of classical conditioning has to await the resolving of th is discordance. (C) 1997 Elsevier Science B.V.