MEG signatures of long-term effects of agreement and disagreement with the majority

www.nature.com/scientificreports OPEN MEG signatures of long‑term effects of agreement and disagreement with the majority A. Gorin1*, V. Klucharev1, A. Ossadtchi2, I. Zubarev3, V. Moiseeva1 & A. Shestakova1 People often change their beliefs by succumbing to an opinion of others. Such changes are often referred to as effects of social influence. While some previous studies have focused on the reinforcement learning mechanisms of social influence or on its internalization, others have reported evidence of changes in sensory processing evoked by social influence of peer groups. In this study, we used magnetoencephalographic (MEG) source imaging to further investigate the long-term effects of agreement and disagreement with the peer group. The study was composed of two sessions. During the first session, participants rated the trustworthiness of faces and subsequently learned group rating of each face. In the first session, a neural marker of an immediate mismatch between individual and group opinions was found in the posterior cingulate cortex, an area involved in conflict-monitoring and reinforcement learning. To identify the neural correlates of the long-lasting effect of the group opinion, we analysed MEG activity while participants rated faces during the second session. We found MEG traces of past disagreement or agreement with the peers at the parietal cortices 230 ms after the face onset. The neural activity of the superior parietal lobule, intraparietal sulcus, and precuneus was significantly stronger when the participant’s rating had previously differed from the ratings of the peers. The early MEG correlates of disagreement with the majority were followed by activity in the orbitofrontal cortex 320 ms after the face onset. Altogether, the results reveal the temporal dynamics of the neural mechanism of long-term 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. Human behaviour is affected by the behaviour of others to a great extent. Conformal behaviour when individuals change their behaviours or beliefs in line with others’ behaviours or b eliefs1, is associated with a number of forms of social influence, e.g. informational (when people looks for the group for guidance) or normative (when people desire approval of the group). Since a pioneering study of conformity by Solomon Asch in 19562, where participants changed their opinion in line with the experimenter’s confederates despite their erroneous response, the impact of social influence on human behaviour became evident not only for professionals in the field of social science1, but also for a wider audience including policy makers. In this study we continue the line of neuroimaging studies of neural substrate of social conformity3. Our group4,5 and other neuroimaging s tudies6 found that social conformity is mediated by reinforcement learning mechanisms and continuous performance monitoring7. Importantly, the involvement of ubiquitous mechanism of prediction-error mechanis 8 mediated by the dopaminergic neural circuitry3,9,10 seems to be implicated in neurobiology of social influence regardless whether it is normative or informational. Moreover, even when individuals want to avoid internal conflicts and preserve consistency in their attitudes, similar neural mechanisms of error-performance monitoring seem to be e ngaged6. A number of functional magnetic resonance imaging (fMRI) studies have confirmed that opinions of others that disagree with one’s own opinions modulate activity of the posterior medial frontal cortex (pMFC), including the anterior part of the cingulate cortex (ACC), the insula, and the ventral striatum3,11–15. Moreover, 1 International Laboratory of Social Neurobiology, Institute of Cognitive Neuroscience, National Research University Higher School of Economics, Moscow, Russia. 2Centre for Bioelectric Interfaces, Institute of Cognitive Neuroscience, National Research University Higher School of Economics, Moscow, Russia. 3Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland. *email: Scientific Reports | (2021) 11:3297 | https://doi.org/10.1038/s41598-021-82670-x 1 Vol.:(0123456789) www.nature.com/scientificreports/ electroencephalographic (EEG) studies have demonstrated differential processing of the opinions of others in terms of whether they agree or disagree with one’s own opinion. More specifically, the effect was manifested in the P200 visual evoked response and was allowed to suggest that to-be-rated stimuli, which had previously been judged similarly with the majority, could attract more perceptual a ttention9. In addition to the P200, a memory recollection associate component known as late positive complex (LPC) peaking at about 600–800 ms after the feedback was modulated by disagreement with the majority16. The conflict of individual and group opinions is often manifested in the feedback-related evoked response, also referred to as feedback-related negativity or FRN17, which has been interpreted as a neural correlate of general reinforcement l earning18. One of the first fMRI studies of conformity revealed that social influence modulated neural activity at the occipital and parietal cortices during a mental rotation task12. This finding was among very first to indicate the private acceptance of peers’ opinions through the modification of sensory processing. A later fMRI s tudy19 specifically investigated the long-term effects of social influence on the neural activity underlying valuation of the stimuli. The exposure to their peers’ opinions affected the participants’ neural representations of the values assigned to faces in the ventral striatum and the OFC. During the second presentation of faces, activity in the OFC and the ventral striatum increased for faces that the group previously rated more favourably than the individual did, as compared to faces that the group rated less favourably. The authors interpreted their finding in light of the true modifications of beliefs and opinions evoked by social influence. This finding supports the concept of social influence emphasizes the rewarding value of social a pproval1. The question as to whether the observed conformal changes of normative behaviour is driven by outward compliance or by the strive to fit peers’ expectations13,20 is still debated. Moreover, the majority of neurocognitive studies regarding social deviance focused on the neural signatures of immediate exposure to group feedback6,9,13,20,21. Up to date, only a few studies attempted to investigate the neural correlates of the long-term effects of social influence, e.g. changes in the stimuli processing after previously experienced social interaction associated with them19,22. Some of them found evidence of long-lasting memory alterations induced by the erroneous grou (...truncated)