Self-other differentiation and monitoring others' actions in the medial prefrontal cortex of the monkey

Abstract

Actions of other individuals are outward manifestations of their unobservable mental states, such as beliefs, desires, and intentions. The correct identification and monitoring of others' actions are of vital importance for determining adaptive behavior in social environments. The neuronal architecture and mechanisms underlying others-action monitoring have been poorly understood. Using two monkeys monitoring each other's actions for their own action planning, we found that one's own actions and the other's actions are coded by largely distinct populations of neurons in the medial prefrontal cortex (MPFC), a key structure in the mentalizing network. Notably, neurons coding the other's actions were significantly more prevalent in a dorsal convexity region (MPFC-convexity), whereas neurons coding one's own actions were significantly more frequent in a ventral, cingulate sulcus region (MPFC-sulcus). Furthermore, a sizable number of MPFC neurons exhibited a phasic increase in activity when another animal made erroneous actions. Such "partner-error" neurons were also distributed in the two segregated regions: the MPFC-convexity, where the other's error was detected, and the MPFC-sulcus, where one's correct action following the other's error was encoded. These findings suggest that the MPFC plays pivotal roles in differentiating between one's own actions and others' actions and in monitoring the correctness of others' actions for adaptive social decisions. Continuing efforts in this research direction will clarify the neuronal basis whereby primates have become such successful social beings in the animal kingdom.