Many have attempted to define mechanisms for stroke recovery in the hope that understanding these processes will improve rehabilitation techniques and enhance function. However, our understanding of how the brain compensates for damage after stroke is uncertain, in part because the relationships between behavior and brain function are not well understood. After stroke some neuroplastic changes are helpful for recovery; others, such as bilateral cortical activity during unimanual movements, have uncertain value. There is limited consensus regarding whether activity in the undamaged, contralesional cortex plays an adaptive role in recovery from stroke, or is an epiphenomenon. It is also unclear what causes activity in the undamaged, contralesional cortex. We propose that contralesional cortical activity is in some part stimulated by task difficulty, and that motor skill acquisition will both reduce perceived effort and alter patterns of brain activation. Thus, the main goal of the proposed study is to map the relationships between the phenomenon of contralesional cortical activation in the stroke affected brain and motor skill acquisition. We predict that motor learning will dynamically alter patterns of brain activation, and reduce contralesional cortical activation. The second goal of this project is to relate functional recovery from stroke with changes in brain activation patterns during motor learning. Because the ability to learn new and relearn old motor skills is essential for recovery after brain damage, we expect that the magnitude of change in contralesional cortical activation associated with motor learning will be related to upper extremity function. To avoid the possibility that changes in brain activation reflect acute physiologic recovery, we will study individuals with chronic middle cerebral artery stroke, using functional magnetic resonance imaging to directly map the relationships between motor-related cortical activation and task-related behavioral improvements that reflect motor learning. ? ?
