Role of medial prefrontal cortex and primary somatosensory cortex in self and other-directed vicarious social touch: a TMS study

Conficting evidence points to the contribution of several key nodes of the ‘social brain’ to the processing of both discriminatory and affective qualities of interpersonal touch. Whether the primary somatosensory cortex (S1) and the medial prefrontal cortex (mPFC), two brain areas vital for tactile mirroring and affective mentalizing, play a functional role in shared representations of C-tactile (CT) targeted affective touch is still a matter of debate. Here, we used offine continuous theta-burst transcranial magnetic stimulation (cTBS) to mPFC, S1 and vertex (control) prior to participants providing ratings of vicarious touch pleasantness for self and others delivered across several body sites at CT-targeted velocities. We found that S1-cTBS led to a signifcant increase in touch ratings to the self, with this effect being positively associated to levels of interoceptive awareness. Conversely, mPFC-cTBS reduced pleasantness ratings for touch to another person. These effects were not specifc for CT-optimal (slow) stroking velocities, but rather they applied to all types of social touch. Overall, our fndings challenge the causal role of the S1 and mPFC in vicarious affective touch and suggest that selfvs other-directed vicarious touch responses might crucially depend on the specifc involvement of key social networks in gentle tactile interactions.