The hands have it: Hand specific vision of touch enhances touch perception and somatosensory evoked potential

Our ability to accurately discriminate information from one sensory modality is often influenced by information from the other senses. Previous research indicates that tactile perception on the hand may be enhanced if participants look at a hand (compared to a neutral object) and if visual information about the origin of touch conveys temporal and/or spatial congruency. The current experiment further assessed the effects of non-informative vision on tactile perception. Participants made speeded discrimination responses (digit 2 or digit 5 of their right hand) to supra-threshold electro-cutaneous stimulation while viewing a video showing a pointer, in a static position or moving (dynamic), towards the same or different digit of a hand or to the corresponding spatial location on a non-corporeal object (engine). Therefore, besides manipulating whether a visual contact was spatially congruent to the simultaneously felt touch, we also manipulated the nature of the recipient object (hand vs. engine). Behaviourally, the temporal cues provided by the dynamic visual information about an upcoming touch decreased reaction times. Additionally, a greater enhancement in tactile discrimination was present when participants viewed a spatially congruent contact compared to a spatially incongruent contact. Most importantly, this visually driven improvement was greater for the view-hand condition compared to the view-object condition. Spatially-congruent, hand-specific visual events also produced the greatest amplitude in the P50 somatosensory evoked potential (SEP). We conclude that tactile perception is enhanced when vision provides non-predictive spatio-temporal cues and that these effects are specifically enhanced when viewing a hand.