Perception of social synchrony induces mother-child gamma coupling in the social brain

The recent call tomove fromfocus on one brain's functioning to two-brain communication initiated a search formechanisms that enable two humans to coordinate brain response during social interactions. Here, we utilized themother-child context as a developmentally salient setting to study two-brain coupling. Mothers and their 9-year-old children were videotaped at home in positive and conflictual interactions. Positive interactions weremicrocoded for social synchrony and conflicts for overall dialogical style. Following,mother and child underwentmagnetoencephalography while observing the positive vignettes. Episodes of behavioral synchrony, compared to non-synchrony, increased gamma-band power in the superior temporal sulcus (STS), hub of social cognition,mirroring andmentalizing. This neural pattern was coupled betweenmother and child. Brain-tobrain coordination was anchored in behavioral synchrony; only during episodes of behavioral synchrony, but not during nonsynchronousmoments, mother's and child's STS gamma power was coupled. Importantly, neural synchrony was not found during observation of unfamiliarmother-child interaction Maternal empathic/dialogical conflict style predictedmothers' STS activations whereas child withdrawal predicted attenuated STS response in both partners. Results define a novel neuralmarker for brain-to-brain synchrony, highlight the role of rapid bottom-up oscillatorymechanisms for neural coupling and indicate that behavior-based processesmay drive synchrony between two brains during social interactions.