Social interactions between attachment partners increase inter-brain plasticity

Inter-brain synchrony between interacting partners is an important feature of social brain function, but whether neural coordination persists beyond the immediate social moment is unknown. Using hyperscanning EEG, we investigated whether a brief mother-adolescent face-to-face interaction induces sustained changes in inter-brain synchrony. We measured neural synchrony in the fronto-temporal network of 110 mothers and adolescents (55 dyads) during co-present resting-state recordings before and after a naturalistic, positively-valanced face-to-face interaction. We found enhanced inter-brain synchrony in the fronto-temporal network following the social interaction, indicating that positive social exchanges can temporarily modify patterns of neural synchrony. The magnitude of this post-interaction neural synchrony was mediated by the partners’ behavioral synchrony during the interaction. Oxytocin increase from pre- to post-interaction predicted the increase in neural synchrony above and beyond behavioral synchrony, suggesting a distinct neuroendocrine path for inter-brain coordination. Results indicate that positive social interactions between attachment partners can induce short-term changes in neural synchrony that persist beyond the immediate exchange. Our findings suggest a potential mechanism by which repeated social experiences within attachment relationships may influence neural development and highlight the need to consider inter-brain dynamics in research on the social foundations of brain development.