?
MEG signatures of remote effects of agreement and disagreement with the majority
People often change their beliefs by succumbing to an opinion of the majority. Such changes are often referred to as majority influence or conformity. While some previous studies have focused on the reinforcement learning mechanisms of conformity or on its internalization, others have reported evidence of changes in sensory processing evoked by majority opinion. In this study, we used magnetoencephalographic (MEG) source imaging to further investigate the remote effects of agreement and disagreement with the majority. During the first session, participants rated the trustworthiness of faces and subsequently learned how the majority of their peers had previously rated each face. To identify the neural correlates of the post-effect of agreeing or disagreeing with the group, we recorded MEG activity while participants rated faces during the next session. We found MEG traces of past disagreement or agreement with the peer group at the parietal cortices as early as approximately 230 ms after the face onset. The neural activity of the superior parietal lobule, intraparietal sulcus, and precuneus was significantly stronger if the participant’s rating had previously differed from the ratings of his or her peers. The early MEG correlates of disagreement with the majority were followed by activity in the orbitofrontal cortex starting at about 320 ms after the face onset. Altogether, the results reveal the temporal dynamics of the neural mechanism of remote effects of disagreement with the peer group: early signatures of modified face processing were followed by later markers of long-term social influence on the valuation process at the ventromedial prefrontal cortex