MODIFIED TEMPORAL BEHAVIOR IN RATS AFTER LARGE HIPPOCAMPAL LESIONS

Rats were trained to work for water under continuous reinforcement and then shifted to a 60-sec fixed-interval schedule. Combined anterior and posterior hippocampal lesions produced higher response rates than only anterior lesions. Animals with anterior lesions and controls were statistically indistinguishable. The stabilized higher fixed-interval rates resulted from a differential rate increase in anticipation of reinforcement. Average response rates were no greater for several seconds after reinforcement but increased differentially towards the end of the interval. This effect cannot be explained by a simple failure of response inhibition. © 1969.