An examination of the effects of mammillary-body lesions on reversal learning sets in monkeys

Abstract

Monkeys with mammillary-body lesions were compared with operated and unoperated control monkeys on the acquisition of a series of place and object reversal discriminations. The animals with mammillary-body lesions were found not to differ from the control animals on either the initial acquisition of a place response or the visual discrimination of two junk objects. On subsequent reversals, however, monkeys with mammillary-body lesions were severely impaired on the spatial task, but showed no impairment in reversal learning in the object task. These results are consistent with our previous findings of an impairment in spatial alternation learning following mammillary-body lesions in monkeys and supports the hypothesis that the role of the mammillary nuclei in cognition may be limited to the spatial domain.