Seeing and feeling the body

Recognizing oneࢠs body as separate from the external world plays a crucial role in detecting external events, and thus in planning adequate reactions to them. In addition, recognizing oneࢠs body as distinct from othersࢠbodies allows remapping the experiences of others onto oneࢠs sensory system, providing improved social understanding. In line with these assumptions, two well-known multisensory mechanisms demonstrated modulations of somatosensation when viewing both oneࢠs own and someone elseࢠs body: the Visual Enhancement of Touch (VET) and the Visual Remapping of Touch (VRT) effects. Vision of the body, in the former, and vision of the body being touched, in the latter, enhance tactile processing. The present dissertation investigated the multisensory nature of these mechanisms and their neural bases. Further experiments compared these effects for viewing oneࢠs own body or viewing another personࢠs body. These experiments showed important differences in multisensory processing for oneࢠs own body, and for other bodies, and also highlighted interactions between VET and VRT effects. The present experimental evidence demonstrated that a multisensory representation of oneࢠs body ࢠunderlie by a high order fronto-parietal network - sends rapid modulatory feedback to primary somatosensory cortex, thus functionally enhancing tactile processing. These effects were highly spatially-specific, and depended on current body position. In contrast, vision of another personࢠs body can drive mental representations able to modulate tactile perception without any spatial constraint. Finally, these modulatory effects seem sometimes to interact with high order information, such as emotional content of a face. This allows oneࢠs somatosensory system to adequately modulate perception of external events on the body surface, as a function of its interaction with the emotional state expressed by another individual.