How the Sense of Body Influences the Sense of Touch

Visual and tactile information interact with each-other, especially when both sensory channels convey information about the same source, that is the body. In the present chapter we reviewed data concerning two forms of visuo-tactile integration specifically linked to the body, namely visual enhancement of touch and visual remapping of touch. If individuals perceive a tactile stimulus while looking at the stimulated body part, tactile perception is boosted, even if vision of the tactile stimulus is prevented. This effect has been called visual enhancement of touch and seems to depend on a modulation the activity of primary somatosensory regions by body-related visual information. Such modulation acts accordingly to a somatotopic organization and might reduce the size of somatosensory receptive fields, thus improving tactile spatial accuracy. A modulation of somatosensory activity can be shown also when individuals see a tactile stimulation administered on the body of others. Observing touch on a face can modulate the perception of tactile stimuli on the observer’s face. We call this effect visual remapping of touch. Here we present a new experimental paradigm to quantify this effect. Using this paradigm, we found that the strength of visual remapping of touch varies systematically as a function of the similarity between the observed and the observer’s face: the effect is maximum when viewing the image of one’s own face being touched; it is stronger when viewing a face of another person belonging the same ethnic or political group as the observer compared to viewing the face of a member a different ethnic or political group.