Context-specific social behavior is altered by orbitofrontal cortex lesions in adult rhesus macaques.

Although the orbitofrontal cortex has been implicated in important aspects of social behavior, few studies have evaluated semi-naturalistic social behavior in nonhuman primates after discrete lesions of this cortical area. In the present report, we evaluated the behavior of adult rhesus monkeys during dyadic social interactions with novel animals following discrete lesions of the orbitofrontal cortex. In a constrained condition, in which animals could engage in only restricted social behaviors, there were no significant differences in social behavior between the lesion group and the sham-operated control group. When the experimental animals could freely interact with partner animals, however, lesioned animals differed from control animals in terms of social interest and fear-related behaviors. These alterations were contingent on the partner with which they interacted. The lesioned animals, when compared to the control animals, had a significantly greater propensity to approach some but not all of their social partners. They also grimaced more towards the partner animal that they did not approach. Behavioral alterations were more apparent during the initial interactions between animals. We discuss these findings in relation to the role of the orbitofrontal cortex in context dependent modulation of social behavior.