Effects of lesions in the amygdaloid nucleus centralis on acquisition and retention of avoidance reflexes in cats.

Acquisition and retention of bar-press avoidance responses after lesions of the lateral part of the amygdaloid nucleus centralis were investigated in 17 adult male cats. The lesions were administered either 10 days (5 cats), or 35 days (7 cats) before training. The remaining 5 cats served initially as intact controls and then, after extensive training, were given similar lesions to test for the effects on retention of the task. The lesions resulted in both retarded avoidance acquisition and a decreased proportion of short latency responses. A short post-operative pause resulted in stronger lesion effects on the length of training and deterioration in short-latency response performance, but a smaller effect on the increase in intertrial responding than was found after a long post-operative pause. The lesioned cats showed more oscillations between runs of escape and avoidance responses than normal, control cats. The immediate effect of lesions on well-trained avoidance reflexes consisted of a decrease in avoidance performance and marked prolongation of escape latencies. The deterioration in short-latency avoidance responding was irreversible in spite of extensive post-operative retraining.