LARGE-SCALE PLASTICITY OF THE HUMAN MOTOR CORTEX

THE adult primate brain is capable of modifying rapidly the size of co rtical receptive fields or motor output modules in response to altered synaptic input. We used positron emission tomography (PET) to map the regional cerebral blood flow changes related to voluntary finger move ments in patients with tumours occupying the hand area of motor cortex . All patients showed activations solely outside the tumour. Compared with the unaffected side, the activations were shifted by 9-43 mm eith er along the mediolateral body representation of motor cortex or into premotor or parietal somatosensory cortex. These results provide evide nce that slowly developing lesions can induce large-scale reorganizati on that is not confined to changes within the somatotopic body represe ntation in motor cortex.