社会的情動の理解に向けて：自己と他者の報酬処理に関する神経機構

抄録

Social emotions such as envy and jealousy are often observed in group-living primates including human beings. Such emotions necessarily depend on others' rewards, but neural mechanisms of reward processing for self and other in the brain remain unraveled. To address this issue, we devised a social Pavlovian conditioning procedure for pairs of monkeys. Despite being constant in amount and probability, the subjective value of forthcoming self-rewards, as indexed by licking and choice behaviors, decreased as partner-reward probability increased. We performed multisite neural recordings in three brain regions involved in processing of social and reward information: the medial prefrontal cortex (MPFC), the dopaminergic midbrain nuclei (DA), and the lateral hypothalamus (LH). MPFC neurons selectively monitored self-reward or partner-reward information, whereas DA neurons integrated this information into a subjective value. LH neurons first encoded a subjective value with bidirectional responses and changed their coding manner similarly to the MPFC. A causality analysis revealed that neural information flowed predominantly in the MPFC-to-DA/LH directions. These findings delineate dedicated pathways for subjective reward evaluation in social environments, which may be neural underpinnings of social emotions.