The effects of total and subtotal prefrontal cortex lesions on the timing ability of the rat

Abstract

Two peak procedure experiments studied the effects of different prefrontal cortex lesions on temporal discrimination in rats. In Experiment 1, lesions were made to either the medial frontal cortex (including medial precentral, anterior cingulate, prelimbic, and infralimbic cortex) or the ventral frontal cortex (including orbital area and agranular insular areal to determine the contribution of each to time estimation. In Experiment 2, lesions were made to the entire prefrontal cortex (including the medial frontal cortex and the ventral frontal cortex). In both experiments, rats were trained with a 40-sec peak interval and tested for 14 postoperative sessions. In Experiment 1, peak time and response distributions showed timing behavior unaffected by either lesion. In Experiment 2, ablations of the prefrontal cortex (PFC) produced a leftward shift in the temporal discrimination functions, indicating that these animals expected the time of reinforcement to be early. Also, these discrimination functions were substantially flattened, which was interpreted as a general decline in timing ability. These results are inconsistent with those of earlier studies. It is concluded that PFC functions as a unit with respect to timing behavior.