Differential Neuroethological Effects of Aversive and Appetitive Reinforcing Stimuli on Associative Learning in Lymnaea stagnalis

Abstract

Abstract It is necessary to determine whether, in the same species and for the same behavior, aversive and appetitive conditioning yield different strengths and periods of either acquisition or retention. To this end, we first examined the effects of various chemo-sensory and physical stimuli on feeding and avoidance behavioral responses in the pond snail, Lymnaea stagnalis. Then, using these findings, we constructed classical-conditioning paradigms with aversive and appetitive stimuli. In the aversive conditioning paradigm, an appetitive stimulus (sucrose), which increased the feeding response, was paired with an aversive stimulus (KCI, quinidine sulfate or electric shock), which inhibited the feeding behavior. Upon presentation of KCI, the first type of aversive conditioning, which is generally called “taste-aversion learning with cessation of feeding response”, was acquired quickly and persisted for up to a month. When using a noxious stimulus (quinidine sulfate or electric shock) inducing pain we addi...