Motor Network Changes Associated With Successful Motor Skill Relearning After Acute Ischemic Stroke: A Longitudinal Functional Magnetic Resonance Imaging Study

Abstract

Background. Motor learning mechanisms may be operative in stroke recovery and possibly reinforced by rehabilitative training. Objectives. To assess early motor network changes after acute ischemic stroke in patients treated with very early mobilization and task-oriented physical therapy in a comprehensive stroke unit, to investigate the association between neuronal activity and improvements in hand function, and to qualitatively explore the changes in neuronal activity in relation to motor learning. Methods. Patients were assessed by functional magnetic resonance imaging and by clinical tests within the first week after stroke and 3 months later. After discharge, all participants were offered functional training of the affected arm according to individual needs. Results. A total of 359 patients were screened, with 12 patients experiencing first-ever stroke, excluding primary sensorimotor cortex (MISI), with severe to moderately impaired hand function fulfilling the inclusion criteria. Laterality indexes (LIs) for MISI increase significantly during follow-up. There is increased cerebellar and striatal activation acutely, replaced by increased activation of ipsilesional MISI in the chronic phase. Bilateral somatosensory association areas and contralesional secondary somatosensory cortex (SII) area are also more active in the chronic phase. Activation of the latter region also correlates positively with improved hand function. Conclusions. Restoration of hand function is associated with highly lateralized MISI. Activity in bilateral somatosensory association area and contralesional SII may represent cortical plasticity involved in successful motor recovery. The changes in motor activity between acute and chronic phases seem to correspond to a motor learning process.