| Abstract: | Repetitive transcranial magnetic stimulation (rTMS) is a non‐invasive brain stimulation technique that may facilitate mechanisms of motor learning. In a recent single‐blind, pseudo‐randomized study, we showed that 5‐Hz rTMS over ipsilesional primary somatosensory cortex followed by practice of a skilled motor task enhanced motor learning compared with sham rTMS + practice in individuals with chronic stroke. However, the beneficial effect of stimulation was inconsistent. The current study examined how differences in sensorimotor cortex morphology might predict rTMS‐related improvements in motor learning in these individuals. High‐resolution T1‐weighted magnetic resonance images were acquired and processed in FreeSurfer using a newly developed automated, whole brain parcellation technique. Gray matter and white matter volumes of the ipsilesional primary somatosensory and motor cortices were extracted. A significant positive association was observed between the volume of white matter in the primary somatosensory cortex and motor learning‐related change, exclusively in the group that received active 5‐Hz rTMS. A regression model with age, gray matter and white matter volumes as predictors was significant for predicting motor learning‐related change in individuals who received active TMS. White matter volume predicted the greatest amount of variance (47.6%). The same model was non‐significant when volumes of the primary motor cortex were considered. We conclude that white matter volume in the cortex underlying the TMS coil may be a novel predictor for behavioral response to 5‐Hz rTMS over the ipsilesional primary somatosensory followed by motor practice. |
