REGIONAL CEREBRAL BLOOD-FLOW CHANGES IN MOTOR CORTICAL AREAS AFTER TRANSIENT ANESTHESIA OF THE FOREARM

To study the effect of deafferentation on cortical areas activated by movement of the proximal muscles, we measured regional cerebral blood flow with positron emission tomography and O-15-labeled water. Flexion -extension movements of the right elbow before deafferentation were as sociated with an increase of regional cerebral blood flow in the prima ry sensorimotor area bilaterally, posterior supplementary motor area b ilaterally, ipsilateral cerebellum, contralateral putamen, premotor ar ea, anterior cingulate area, and posterior parietal region. Transient anesthesia of the right forearm induced by ischemic block caused an in crease of regional cerebral blood flow in the primary sensorimotor are a bilaterally at rest, but there was no change of regional cerebral bl ood flow with movement, indicating that the movement-related change in cerebral blood how was reduced. These findings are consistent with in creased excitability of neurons as a result of deafferentation. In the supplementary motor area, anesthesia did not induce any change in reg ional cerebral blood flow at rest, but there was a decline with moveme nt, again indicating a reduction of the change in cerebral blood flow related to movement. This might be due to a reduction in sensory feedb ack because of the anesthesia.