Face or hand, not both: perceptual correlates of reafferentation in a former amputee.

The topography of the somatosensory maps of our body can be largely shaped by alterations of peripheral sensory inputs. Following hand amputation, the hand cortical territory becomes responsive to facial cutaneous stimulation. Amputation-induced remapping, however, reverses after transplantation, as the grafted hand (re)gains its sensorimotor representation. Here, we investigate hand tactile perception in a former amputee by touching either grafted hand singly or in combination with another body part. The results showed that tactile sensitivity recovered rapidly, being remarkably good 5 months after transplant. In the right grafted hand, however, the newly acquired somatosensory awareness was strikingly hampered when the ipsilateral face was touched simultaneously, i.e., right face perception extinguished right hand perception. Ipsilateral face-hand extinction was present in the formerly dominant right hand 5 months after transplant and eventually disappeared 6 months afterwards. Control conditions' results showed that right hand tactile awareness was not extinguished either by contralateral left face and left hand stimulation or ipsilateral stimulation of the arm, which is bodily close to, but cortically far from, the hand. We suggest that ipsilateral face-hand extinction is a perceptual counterpart of the remapping that occurs after allograft and eyewitnesses the inherently competitive nature of sensory representations.