rpSTS Stimulation Disrupts Shared Neural Responses to Social Content during Naturalistic Viewing

Shared understanding of common experiences can foster feelings of social closeness and friendship, and help us understand those experiences. Recent work has suggested that patterns of neural activity shared across individuals, especially throughout the default mode network, may underlie shared representations. Here we used repetitive transcranial magnetic stimulation (rTMS) and functional magnetic resonance imaging during movie watching to show that shared neural patterns to common experiences rely on the encoding of social information from the environment by the right posterior superior temporal sulcus (rpSTS). An encoding model of movie features showed that rTMS selectively degraded social feature encoding in rpSTS, leaving low-level visual encoding in early visual cortex intact. Using natural language processing (NLP)-based analysis, we found that rpSTS stimulation was associated with reduced memory and intersubject pattern similarity across DMN and limbic networks during scenes central to the movie narrative. Projecting scene embeddings onto NLP-based concept axes revealed reductions in memory and neural pattern similarity for scenes conveying helplessness and empathy following rTMS. These findings provide causal evidence that the rpSTS is a key region that encodes shared social information into common neural representations, and suggest that disrupting its input leads DMN representations to become idiosyncratic.