The neural substrates of motor recovery after focal damage to the central nervous system

Objective: To discuss how reorganization of the surviving central nervous system tissue might subserve the improvements in function that are commonly seen over weeks, months, and sometimes years after stroke. Data Sources: Original scientific studies. Study Selection: The studies reviewed all used noninvasive techniques such as functional magnetic resonance imaging, electroencephalography, magnetoencephalography, and transcranial magnetic stimulation. Only studies using motor paradigms in stroke patients were reviewed. Data Extraction: Data were reviewed and assessed by the author. Data Synthesis: Currently, results suggest that functionally relevant changes do occur in cerebral networks in human stroke patients. For example, it is apparent that initial attempts to move a paretic limb after stroke are associated with widespread activity within the distributed motor system in both cerebral hemispheres. This reliance on nonprimary motor output pathways is unlikely to support full recovery, but improved efficiency of the surviving networks is associated with behavioral gains. Conclusions: This review discusses how a better understanding of the relation between these changes and recovery will facilitate the development of novel therapeutic techniques that are based on neurobiologic principles and that are designed to minimize impairment in appropriately targeted patients suffering from stroke.