Corticomuscular Coherence in Post-Stroke Motor Function and Recovery

Background: Assessing cortical and muscle activity simultaneously during task performance may inform motor function post-stroke. This study evaluated brain–muscle functional connectivity (corticomuscular coherence, CMC) in early stroke recovery. Methods: Individuals with stroke in an inpatient rehabilitation facility (IRF) completed motor assessments and simultaneous electroencephalography (EEG) and electromyography (EMG) recordings during a grip task at IRF admission and discharge. Beta (20–30 Hz) CMC was measured between EEG electrodes overlying the primary motor cortex (M1) and supplementary motor area (SMA) and EMG leads overlying the first dorsal interosseous (FDI). Neurotypical controls completed identical EEG/EMG recordings. Correlational analyses were performed to ascertain CMC and motor assessment associations. CMC differences by Group (Stroke vs. Controls), Time (Admission vs. Discharge), and Extremity (Affected/Dominant vs. Less Affected/Non-Dominant) were estimated using mixed-effects linear models. Results: Thirty individuals with stroke (14 females, mean age 67.0 ± 9.8 years, 10.4 ± 3.5 days post-stroke) and 17 controls (8 females, mean age 75.3 ± 13 years) participated. Individuals with stroke exhibited reduced beta CMC between SMA and affected FDI (F(1,36.1) = 5.73, p = 0.02, Cohen’s f = 0.40) compared to controls, with lower CMC involving the affected vs. less affected extremity (F(1,73.0) = 5.72, p = 0.01, Cohen’s f = 0.28). Greater beta SMA–FDI CMC at admission related to poorer motor recovery (ρ = −0.59, p = 0.01). Group and Extremity CMC differences were not observed over time, nor were there changes in affected extremity CMC from admission to discharge. Conclusions: Beta SMA–FDI CMC is a marker of neural injury, exhibiting extremity-specific differences early post-stroke. While beta SMA–FDI CMC correlated with motor recovery, the absence of change over time during hospitalization necessitates longitudinal assessments to clarify its trajectory alongside recovery.