Beta-Band Cortico-Muscular Phase Coherence in Hemiparetic Stroke

During the post-stroke recovery process, the brain undergoes reorganization, compensating for the loss of ipsilesional corticospinal and corticobulbar pathways, resulting in increased contralesional activity during paretic arm movement tasks. A better understanding of the mechanisms behind this may enhance motor recovery assessments, providing insight into the extent of post-stroke contralesional motor cortical adaptation. This proof-of-concept study involves eight healthy controls and ten post-stroke participants. Electroencephalographic (EEG) and deltoid electromyographic (EMG) data was collected from each participant during the performance of an upper-limb shoulder abduction task. Phase coupling between beta-band motor cortex EEG and deltoid muscle EMG was assessed using Multi-Phase Locking Value (M-PLV). Using the calculated EEG-EMG phase coherence, nerve conduction delay from the contralateral motor cortex to the deltoid muscle of the paretic arm was estimated for all participants. Our results show several differences between post-stroke and control participants; ipsilateral (stroke-contralesional) motor cortex beta-band phase coherence behavior is altered in post-stroke participants, showing a significant difference in ipsilateral EEG-EMG coherence values, ipsilateral time course percentage above the significance threshold, and ipsilateral time course area above the significance threshold. M-PLV analysis provides evidence for post-stroke contralesional motor cortex adaptation, highlighting its increased role in the paretic shoulder abduction task. Nerve conduction delay between the motor cortexes and deltoid muscle is significantly higher in stroke participants. Beta-band M-PLV phase coherence analysis shows greater phase-coherence distribution convergence between ipsilateral and contralateral motor cortices in stroke participants, potentially indicative of maladaptive neural adaptation resulting from a greater reliance on the contralesional motor cortex.