DISTINCT ROLES OF TWO FRONTAL AREAS IN THE PREDICTION OF OTHERS’ ACTIONS

Predicting others’ actions is a cornerstone of successful social exchanges. In this study, we sought to clarify how two frontal core nodes in the social brain network, the ventral premotor cortex (PMv) and the medial prefrontal cortex (MPFC), are involved in the prediction of others’ actions. To this end, we examined neuronal activities in these areas while macaque monkeys performed a turn-taking choice task. In this task, a monkey undergoing neural recording (designated as M1) faced a partner monkey (designated as M2) indirectly through a video device. This device allowed manipulation of visual information about M2’s actions provided to M1 while ensuring real-time social interactions. In approximately 15% of M2-actor trials, the reaching movement was entirely occluded from M1’s sight using the video device (occluded trials). We found that as many as 25% and 45% of task-related neurons in the PMv and MPFC, respectively, were preferentially activated in the occluded trials. While many of these neurons in the PMv were activated during or after M2’s choice, those in the MPFC were predominantly activated immediately after the onset of an occlusion stimulus. The majority of the occlusion-responsive neurons exhibited significantly attenuated responses when the occlusion stimulus was presented outside the task context. These results suggest that the PMv and MPFC primarily contribute to predicting ongoing and upcoming actions of others, respectively.