Alleviating the 'crossed-hands' deficit by seeing uncrossed rubber hands.

Localizing and reacting to tactile events on our skin requires the coordination between primary somatotopic projections and an external representation of space. Previous research has attributed an important role to early visual experience in shaping up this mapping. Here, we addressed the role played by immediately available visual information about body posture. We asked participants to determine the temporal order of two successive tactile events delivered to the hands while they adopted a crossed or an uncrossed-hands posture. As previously found, hand-crossing led to a dramatic impairment in tactile localization, which is a phenomenon attributed to a mismatch between somatotopic and externally-based frames of reference. In the present study, however, participants watched a pair of rubber hands that were placed either in a crossed or uncrossed posture (congruent or incongruent with the posture of their own hands). The results showed that the crossed-hands deficit can be significantly ameliorated by the sight of uncrossed rubber hands (Experiment 1). Moreover, this visual modulation seemed to depend critically on the degree to which the visual information about the rubber hands can be attributed to one's own actions, in a process revealing short-term adaptation (Experiment 2).