Comparison of Differential Pavlovian Conditioning in Whole Animals and Physiological Preparations of Pleurobranchaea: Implications of Motor Pattern Variability

摘要

The present study compares differential Pavlovian conditioning in whole animals with the behavior of the same animals during electrophysiological recording. Untrained specimens of the sea slug Pleurobranchaea did not discriminate between two appetitive stimuli, one derived from an extract of beer (Sbr) and the other from a homogenate of squid muscle (Ssq). When animals received Sbr as the CS(+) and Ssq as the CS(-) in a single day of five-trial, differential Pavlovian conditioning they learned to avoid selectively the Sbr but continued to exhibit appetitive responses to Saq. Quantitative measures show that there was over a 1000-fold increase in the thresholds of the probosics extension and bite-strike responses, many animals ceased all feeding behavior, and exhibited withdrawal responses to Sbr. Unexpectedly, motor patterns from untrained preparation at different times and between preparations; conditioning appeared to increase such variability. Thus, it was not possible to state unequivocally the behavior of the animal by examining the electromyogram recording alone. Many of the trained preparations not only exhibited suppressed feeding behavior and withdrawal responses to Sbr, but, as a consequence of the multifunctional nature of the Pleurobranchaea buccal-oral system, also regurgitated previously ingested Saq or squid meat when they were stimulated with Sbr.