Perseveration in extinction and in discrimination reversal tasks following selective frontal ablations in Macaca mulatta

Abstract

In order to determine whether the perseverative syndrome exhibited by monkeys with frontal lobe lesions can be fractionated by partial frontal lesions, monkeys with dorsolateral frontal lesions, those with orbital frontal lesions, and those with partial orbital lesions were tested in three tasks: extinction of a food rewarded bar pressing response, spatial discrimination reversals and object discrimination reversals. Perseveration of bar-pressing in extinction was selectively related to the posteromedial or "limbic" portion of orbital frontal cortex. Deficits in object discrimination reversal, on the other hand, were specifically associated with the lateral sector of orbital cortex and possibly to the adjoining ventral portion of dorsolateral frontal cortex as well. Impairment in spatial discrimination reversal was most severe in monkeys with dorsolateral frontal removal. These findings suggest that the perseverative effects of orbital frontal ablation can be fractionated into at least two components and further support the view that dorsolateral frontal cortex is associated with spatial factors.