Quality of stimuli and prefrontal lesions effects on reversal learning in go-no go avoidance reflex differentiation...

Go – no go avoidance reflex differentiation of two acoustic stimuli has been previously established in cats. Then the signalling properties of the conditioned stimuli were reversed and the course of acquisition of a new go-no go differentiation was studied in normal cats and in cats with prefrontal lesions. The hypothesis based on stimulus intensity dynamism theory was: (i) in normal cats acquisition of the new differentiation would be easier if the more effective stimulus of the pair were used as the positive stimulus, and (ii) in prefrontal cats this effect of stimulus quality would be l a or absent. Results confirmed both predictions. The differences in rapidity of reversal learning were almost exclusively due to differences in responding to the new positive stimulus. Prefrontal cats were not deficient in comparison with normal cabs in their inhibitory abilities in spite of the fact that extinction of bar-pressing to the new negative conditioned stimulus was much slower than trader of the avoidance response to the new positive stimulus. At the beginning of reversal learning two opposite changes in responding on no-go trials were observed: (i) a decrease in the number of long-latency responses, which reflected the changed signalling value of the previously positive stimulus, and (ii) an increase in the number of short-latency responses, which was positively correlated with the increase in rate of intertrial responding. The increases in number of short-latency responses to the new negative stimulus and in rate of intertrial responding observed at the beginning of reversal learning were smaller in prefrontal than in normal cabs. Results of the experiment indicate that the "drive disinhibition hypothesis" does not account for the effects of prefrontal lesions on avoidance behavior.