SOMATOSENSORY CORTICAL PLASTICITY IN ADULT HUMANS REVEALED BY MAGNETOENCEPHALOGRAPHY

Microelectrode recordings in adult mammals have clearly demonstrated t hat somatosensory cortical maps reorganize following peripheral nerve injuries and functional modifications; however, such reorganization ha s never been directly demonstrated in humans. Using magnetoencephalogr aphy, we have been able to demonstrate the somatotopic organization of the hand area in normal humans with high spatial precision. Somatosen sory cortical plasticity was detected in two adults who were studied b efore and after surgical separation of webbed fingers (syndactyly). Th e presurgical maps displayed shrunken and nonsomatotopic hand represen tations. Within weeks following surgery, cortical reorganization occur ring over distances of 3-9 mm was evident, correlating with the new fu nctional status of their separated digits. In contrast, no modificatio n of the somatosensory map was observed months following transfer of a neurovascular skin island flap for sensory reconstruction of the thum b in two subjects in whom sensory transfer failed to occur.