PAVLOVIAN APPETITIVE DISCRIMINATIVE CONDITIONING IN APLYSIA-CALIFORNICA

Three experiments demonstrated Pavlovian appetitive discrimination lea rning in the marine mollusc, Aplysia californica. In each experiment, subjects were exposed to two conditioned stimuli; one stimulus (CS+) w as paired with food presentations and the other stimulus (CS-) was nev er followed by food. In Experiments 1 and 3 different chemosensory sti muli were used, and in Experiment 2 different tactile stimuli were use d. For both types of conditioned stimuli, bite responses occurred sign ificantly more often to the CS than to the CS-. Experiment 2 also show ed that Aplysia could learn a reversal of this discrimination. Experim ent 3 showed that nonreinforced presentations of CS+ resulted in a dec line in the frequency of conditioned biting. The implications of these results for neurobiological analyses of learning are discussed.