Neural populations in macaque anterior cingulate cortex encode social image identities.

The anterior cingulate cortex gyrus (ACCg) has been implicated in prosocial behaviors and reasoning about social cues. While this indicates that ACCg is involved in social behavior, it remains unclear whether ACCg neurons also encode social information during goal-directed actions without social consequences. To address this, we assessed how social information is processed by ACCg neurons in a reward localization task. Here we show that neurons in the ACCg of female rhesus monkeys differentiate the identities of conspecifics in task images, even when identity was task-irrelevant. This was in contrast to the prearcuate cortex (PAC), which has not been strongly linked to social behavior, where neurons differentiated identities in both social and nonsocial images. Many neurons in the ACCg also categorically distinguished social from nonsocial trials, but this encoding was only slightly more common in ACCg compared to the PAC. Together, our results suggest that ACCg neurons are uniquely sensitive to social information that differentiates individuals, which may underlie its role in complex social reasoning.