Role of prefrontal and anterior temporal cortex in social behavior and affect in monkeys

Prefrontal or anterior temporal but not cingulate cortex lesions lead to major deficits in all aspects of social behavior including maternal protectiveness, aggressiveness, group cohesiveness, defense of territory, maintenance of hierarchical status, and, even, sexual behavior. Lesions of visual association cortex, on the other hand, fail to produce such deficits. Rather, these deficits appear to be spedfically emotional in nature and not related to impairments in perceptual or sensory functions. Prefrontal and anterior temporal cortical lesions also produce major losses in both facial expressions and in vocalizations suggesting these functions in the rhesus monkey participate primarily in emotional and socia1 communications. In keeping with this interpretation, present studies show a major difficulty in bringing rhesus monkey vocalizations under instrumental or conditioned control. Thus, in this species, there exists a major difficulty of access between the volitional control mechanisms of the cortex and the vocalization apparatus. The present findings support the hypothesis of a duel control of the face and voice in man whereby there still exists prominently the emotional or affective element which mediates all involuntary or spontaneously emotive expressions of feeling. This more primitive and aged mechanism for face and voice control utilizes quite different neural control mechanisms than does the more recently derived system which provides for a volitional face and voice control. This more recent system has developed embedded wlithin the posteriorly located analytic and mnemonic cortical tissues and provides for communications between individuals within the species at symbolic, verbal levels.