Perseveration in the rat following hippocampal lesions

Abstract

Animals with either bilateral hippocampal or amygdala lesions and non-operated controls were compared on acquisition of a Sidman avoidance task under two conditions of prior experience. In one condition of prior experience the three groups of animals were trained to bar-hold in a shock-escape task and this pretraining was followed by the avoidance task which required repetitive bar-pressing. In the other condition, no pretraining was given before the avoidance task was introduced. Analysis of the shock-reduction and response patterning data during the avoidance task suggested that there was a differential effect of the pretraining on the animals with hippocampal lesions. These animals also manifested a significant increase in bar-holding during the avoidance task. The results suggest that hippocampal lesions produce a deficit in the giving up of old responses rather than in the learning of new ones.