Self and other in the somatosensory system.

The observation of touch on another person’s body automatically activates brain regions directly involved in tactile perception. This suggests that in order to understand sensations experienced by others, observers remap visual information onto their own somatosensory system. We developed an experimental paradigm to study whether such remapping is modulated by perceptual or social factors. Subjects observe a visual stimulus being touched by hands while receiving tactile stimuli on their face. Observing a face, but not an object, enhanced the detection of sub-threshold tactile stimuli on the face. This effect was stronger when subjects viewed their own face rather than another person’s face. The strength of the effect due to viewing the face of others depended on the similarity between the observer and the observed face: tactile detection was higher when young observers viewed young rather than elderly faces. The pleasantness of the observed face also modulated the effect: viewing one’s own face, or another person’s face, morphed to increase face beauty, enhanced tactile perception. Therefore high order perceptual and social factors, such as similarity or attractiveness of the observed face, modulate visual remapping of touch. These findings suggest that in condition of interaction between self and other, top-down processes modulate multisensory integration.