Beta-Band Corticomuscular Coherence: A Novel Biomarker of Functional Corticospinal Tract Integrity and Motor Recovery After Stroke

Upper-limb motor impairment following stroke predominantly results from the damage to corticospinal tract (CST) integrity. Current clinical assessments of CST integrity face significant limitations, including high costs, specialized equipment, and inability to guide state-dependent closed-loop rehabilitation therapies. Corticomuscular coherence (CMC), which measures the functional coupling between sensorimotor cortical rhythms and muscular activity, represents a potentially accessible, and clinically feasible alternative for evaluating CST damage in stroke patients. However, it remains unclear whether CMC is a reliable biomarker of CST integrity and poststroke motor recovery. To address this issue, we measured electroencephalography (EEG), electromyography (EMG) and motor-evoked potential (MEP) status from subacute patients during grip and finger extension tasks performed with both affected and unaffected hands. Using a multivariate analysis approach, we identified abnormal modulations of CMC and event-related desynchronization (ERD), characterized by frequency-specific disruptions and distinctive spatial distributions. Crucially, our results also demonstrated that CMC reflects neurophysiological mechanisms distinct from cortical activation. Further analysis revealed significant CMC differences between patient groups stratified by MEP status, and confirmed the predictive value of CMC features for assessing functional CST integrity. Additionally, there existed significant associations between beta-band CMC and clinical motor assessments. These findings highlight the potential utility of CMC as a valuable tool for assessing functional CST integrity and motor recovery after stroke.