TRAINING IN A NOVEL ENVIRONMENT IMPROVES THE APPETITIVE LEARNING-PERFORMANCE OF THE SNAIL, LYMNAEA-STAGNALIS

The effect of novelty, an environmental background variable affecting feeding and appetitive learning performance, was examined in a behavioral study of the pond snail Lymnaea stagnalis. Transfer of snails into a novel aquatic environment (clean water) evoked exploratory behavior which manifested itself in an increased number of spontaneous rasping movements of the mouth over the second to fifth minute after exposure to the novel environment. The intensity of this behavior was much weaker in a familiar environment (used water from the home tank). Similarly, sucrose-induced feeding rates were highest when the snails were given the sucrose stimulus in a novel environment. The effectiveness of appetitive conditioning using tactile stimulus paired with food (Kemenes and Benjamin, 1989a) improved when the snails were subjected to conditioning in a novel environment. Satiety, an internal variable, suppressed the stimulating effects of the novel environment on the spontaneous, unconditioned, and conditioned feeding alike. After training in the novel environment, the conditioned response was retained for up to 12 days and thus provided a robust behavioral paradigm for the extension of the analysis to the neurophysiological mechanisms of factors affecting appetitive learning in molluscs. (C) l994 Academic Press,Inc.