Embodied empathy for tactile events: Interindividual differences and vicarious somatosensory responses during touch observation

A growing body of evidence suggests an involvement of the somatosensory cortices for social perception. For example, it has been shown that observing touch on other bodies (in the absence of any real touch on the own body) affects somatosensory brain areas. Thus, understanding others' sensory experiences seems to rely on vicarious activation of somatosensory cortices. Recent studies also demonstrated that observation of painful and nonpainful touch engages the observer's somatosensory cortex differentially. The somatosensory activation during observation of painful stimulation has been related to trait differences in empathy, thereby drawing the attention to inter-individual differences in vicarious somatosensory activation. The current study aims to test the hypothesis if vicarious somatosensory activation during observation of nonpainful touch is also linked to inter-individual differences in empathy. We employed a functional magnetic resonance imaging (fMRI) paradigm to present video clips showing simple non-painful touch with a paintbrush to a hand relative to a control condition including the same visual and motion parts. Results revealed vicarious somatosensory activation when seeing the hand being touched. This activation was associated with trait differences in interpersonal reactivity. Thus, we found that the somatosensory response in primary somatosensory cortex (SI) was associated with the empathy subscale perspective taking. This link demonstrates that vicarious somatosensory responses for simple touch are influenced by the observer's personality traits, therefore suggesting a role for personality traits in a putative mirror neuron system.