Neural similarity between mentalizing and live social interaction

Reciprocal social interactions are a quintessential part of human life, yet little neuroimaging research has examined the underlying neurocognitive mechanisms using social interactive experimental paradigms. Recent work using social interactive tasks has demonstrated brain activity in the mentalizing network, even in the absence of explicit mentalizing demands, suggesting that social interactive contexts automatically engage mentalizing. However, while overlapping brain activations are suggestive of similar underlying neural processes between explicit mentalizing and spontaneous mentalizing during interaction, they are not a direct test of whether or not these processes are represented similarly in the brain. Pattern-based approaches provide the sensitivity to examine the similarity between different neurocognitive processes. The current study used representational similarity analysis on a task wherein participants made mental and non-mental judgments about an abstract character and a live, social interactive partner during fMRI. The within-subject, 2 (Mental/Non-mental) x 2 (Peer/Character) design enabled us to examine the similarity in response patterns between conditions across numerous brain regions associated with social cognition, and estimate fit to three theoretical models of how the two processes relate: 1) social interaction and explicit mentalizing about an abstract character are represented similarly; 2) interactive peer and abstract character are represented differently regardless of the evaluation type; and 3) mental and non-mental states are represented dissimilarly regardless of target. Results demonstrate that the temporal poles and the right posterior superior temporal sulcus represent mentalizing and peer interactions similarly (Model 1), suggesting that response patterns in these regions provide a link between mentalizing and social interaction. Much of the rest of the social brain exhibits different representations for interactive peers and abstract characters (Model 2). Finally, model-free analyses showed that different regions show sensitivity to either the interaction partner or story character. Together, our findings highlight the importance of studying social cognitive processes using interactive approaches, and the utility of pattern-based approaches in understanding how social cognitive processes relate to each other.