The Social Cerebellum and Human Interactions

Abstract

Research in the past 5 years has provided growing evidence supporting the view that the posterior cerebellum is involved in social mentalizing (i.e., theory of mind). We investigated the hypothesis that the posterior cerebellum builds internal action models of our social interactions to predict how other people’s actions will be executed, and what our most likely responses to these actions will be. We developed novel social sequencing tasks that involved a combination of (a) learning or generating chronological sequences of social actions either in an explicit or implicit manner, which (b) require social mentalizing on another person’s mental state such as goals, beliefs, and implied traits. Together, the fMRI results unequivocally confirm the central role of the posterior cerebellar Crus 2 in identifying and automatizing action sequencing during social mentalizing, and in predicting future action sequences based on social mentalizing inferences about others. These findings provided the incentive to investigate non-invasive neurostimulation with healthy participants targeting the posterior cerebellum. Both transcranial magnetic stimulation (TMS) as well as transcranial direct current stimulation (tDCS) showed beneficial effects on social sequencing tasks, as participants generated correct social action sequences quicker. These stimulation techniques guided by novel cerebellar social sequencing insights might have the potential to increase posterior cerebellar plasticity and alleviate social impairments in mental disorders.