The role of the medial prefrontal cortex (mPFC) in social decision-making against high- and low-rank opponents: a transcranial direct current stimulation (tDCS) study.

Abstract

Social hierarchy is a key determinant of behavior and individuals interact with others based on their social rank. Previous research has emphasized the role of the mPFC in learning social hierarchies. This study employed a social rank learning task alongside a modified version of the Ultimatum Game (UG) to investigate how individuals respond to monetary offers from different social ranks and whether the mPFC modulates these reactions. Our findings indicate that unfair offers are more likely to be rejected and offers made by individuals of lower social rank are more likely to be rejected compared to those from higher social rank. Additionally, men tend to respond quicker than women in the UG. Remarkably, participants who received tDCS over the mPFC demonstrated higher rejection rates and faster response times for offers of low-rank individuals, while the lower rejection rates and slower responses to offers from high-rank opponents. These results shed light on the neural mechanisms involved in social decision-making in competitive contexts. In particular, they reveal increased sensitivity of the mPFC to social ranks after electrical stimulation, which might be an evidence for its role in shaping decisions and reactions toward unfairness within the existing social hierarchies.