Cortical plasticity after stroke: implications for rehabilitation.

While adaptive processes in the cerebral cortex have long been thought to contribute to functional recovery after stroke, the precise neuronal structures and mechanisms underlying these processes have been difficult to identify. Over the past 15 years, a large number of studies conducted in human stroke patients and in experimental animal models have contributed to a more coherent picture of the brain's adaptive capacity after injury. These studies suggest that the cerebral cortex undergoes significant and functional structural plasticity for at least several weeks to months following injury. Adaptive changes have been demonstrated in the intact tissue surrounding the lesion, as well as in other cortical motor areas remote from the site of injury. Recent results from non-human primate studies of cortical reorganization after stroke demonstrate marked functional changes in the intact cortical tissue adjacent to the infarct in the weeks following an ischemic lesion. Further, intensive task-specific practice with the impaired limb has a modulatory effect on the inevitable cortical plasticity. Taken together with parallel studies of forced use in human stroke patients, it is likely that use of the impaired limb can influence adaptive reorganizational mechanisms in the intact cerebral cortex, and thus, promote functional recovery.