Cortical plasticity after stroke: implications for rehabilitation

While adaptive processes in the cerebral cortex have long been thought to c ontribute to functional recovery after stroke, the precise neuronal structu res and mechanisms underlying these processes have been difficult to identi fy. Over the past 15 years, a large number of studies conducted in human st roke patients and in experimental animal models have contributed to a more coherent picture of the brain's adaptive capacity after injury. These studi es suggest that the cerebral cortex undergoes significant functional and st ructural plasticity for at least several weeks to months following injury. Adaptive changes have been demonstrated in the intact tissue surrounding th e lesion, as well as in other cortical motor areas remote from the site of injury. Recent results from non-human primate studies of cortical reorganiz ation after stroke demonstrate marked functional changes in the intact cort ical tissue adjacent to the infarct in the weeks following an ischemic lesi on. Further, intensive task-specific practice with the impaired limb has a modulatory effect on the inevitable cortical plasticity. Taken together wit h parallel studies of forced use in human stroke patients, it is likely tha t use of the impaired limb can influence adaptive reorganizational mechanis ms in the intact cerebral cortex, and thus, promote functional recovery.