Stuck on you! Social brain stimulation increases the cognitive effort required to return to the egocentric perspective.

Flexible switching between self and other perspectives is critical for adaptive social cognition and is thought to rely on the dynamic regulation of self-other representations. Although neuroimaging implicates the dorsomedial prefrontal cortex (dmPFC) and right temporoparietal junction (rTPJ) in perspective-taking, causal evidence for their contributions to perspective switching is lacking. Here, we applied focal transcranial direct current stimulation (f-tDCS) to the dmPFC and rTPJ while participants completed a visual perspective-taking task requiring switches between egocentric and altercentric viewpoints. Anodal stimulation to either site selectively increased the cognitive cost of switching back to the egocentric-perspective, without affecting switches into the altercentric-perspective. Rather than facilitating re-engagement with self-referential processing, stimulation enhanced altercentric persistence or impaired disengagement from the altercentric perspective. These findings provide novel causal evidence that both the dmPFC and rTPJ are involved in regulating the inhibition and updating of self-other representations during perspective switching. Results suggest that stimulation of these hubs may disrupt efficient realignment to the self, highlighting their role in maintaining an altercentric cognitive state. Future studies are required to uncover the precise neural computations that account for the comparable behavioural outcomes observed across distinct social brain hubs.