Understanding others' feelings: The role of the right primary somatosensory cortex in encoding the affective valence of others' touch

Brain imaging studies in humans have shown the existence of a shared somatosensory representation in the primary somatosensory cortex (S1), putatively involved in understanding others' sensations (Keysers et al., 2010); however, the role of S1 in such a high-level process is still unknown. To ascertain the causal involvement of S1, and its possible hemispheric lateralization, in encoding the affective valence of emotional scenes, depicting, or not, a tactile event, we gave to healthy participants a picture-based affective go/no-go task and low-frequency repetitive transcranial magnetic stimulation (rTMS). The dorsolateral prefrontal cortex (DLPFC) was chosen as control site. rTMS over the right, but not the left, S1 selectively increased the participants' latencies in the affective go/no-go task, but only when the affective state was conveyed by touch; intriguingly, this interfering effect was associated with the empathic ability to adopt the subjective perspective of others. The left, not the right, DLPFC is also involved in affective go/no-go performance, but regardless of the sight of touch, and independently of empathic abilities. This novel evidence demonstrates the crossmodal role of right S1 in encoding the pleasant and aversive consequences of others' sensations evoked by touch.