Neural representations of observed interpersonal synchrony/asynchrony in the social perception network

The visual perception of individuals is thought to be mediated by a network of regions in occipitotemporal cortex that supports specialized processing of faces, bodies, and actions. In comparison, we know relatively little about the neural mechanisms that support the perception of multiple individuals and the interactions between them. The present study sought to elucidate the visual processing of social interactions by identifying which regions of the social perception network represent interpersonal synchrony. In an fMRI study with 32 human participants (26 female, 6 male), we used multi-voxel pattern analysis to investigate whether activity in face-selective, body-selective, and interaction-sensitive regions across the social perception network supports decoding of synchronous vs. asynchronous head-nodding and head-shaking. Several regions were found to support significant decoding of synchrony/asynchrony, including extrastriate body area, face-selective and interaction-sensitive mid/posterior right superior temporal sulcus, and occipital face area. We also saw robust cross-classification across actions in extrastriate body area, suggestive of movement-invariant representations of synchrony/asynchrony. Exploratory whole-brain analyses also identified a region of right fusiform cortex that responded more strongly to synchronous than asynchronous motion. Critically, perceiving interpersonal synchrony/asynchrony requires the simultaneous extraction and integration of dynamic information from more than one person. Hence, the representations of synchrony/asynchrony cannot be attributed to augmented or additive processing of individual actors. Our findings therefore provide crucial new evidence that social interactions recruit dedicated visual processing within the social perception network that extends beyond any domain-specific processing engaged by the faces and bodies of individual agents.