Corticomuscular Connectivity and Brain Reorganization Post-Stroke

Stroke often causes damage to the motor descending pathways in the lesioned hemisphere, resulting in compensatory recruitment of contralesional motor resources. This proof-of-concept study examines how motor task demand affects brain-muscle communication in individuals with chronic stroke, which represents motor system remodeling after the injury. Coherence between EEG and deltoid EMG was estimated during an isometric shoulder abduction task, and hemisphere dominance was evaluated using a Laterality Index (LI) in five stroke survivors and five healthy controls during isometric shoulder abduction at 20% and 40% of maximal voluntary contraction. Compared to controls, stroke participants exhibited a significantly reduced beta-band corticomuscular connectivity (CMC) at the lesioned hemisphere, with enhanced contralesional CMC. This was accompanied by an increase in motor demand, which amplified contralesional cortical involvement and revealed a pronounced shift in the Laterality Index (LI) toward contralesional dominance. This shift is indicative of maladaptive neural reorganization and diminished reliance on the ipsilesional hemisphere. The potential of beta-band CMC and LI as sensitive neurophysiological biomarkers for evaluating motor impairment and guiding individualized neurorehabilitation strategies that account for cortical plasticity and load-dependent recruitment patterns in stroke recovery is underscored by these task-dependent alterations in coherence and hemispheric dominance.