Validation of Low-Frequency Oscillatory Activity as an Indicator of Post-Stroke Injury and Recovery

Background This study investigated the roles of delta (1-3 Hz) and beta (20-30 Hz) electroencephalography (EEG) oscillatory activity at rest in post-stroke recovery. Driven by previous work linking delta and beta activity with stroke-related injury and motor recovery, this study sought to validate these findings in an independent cohort, addressing the need for confirmatory studies in stroke biomarker development. Methods Individuals with stroke admitted to an inpatient rehabilitation facility along with a control group of unimpaired adults were recruited. Participants completed motor assessments and two EEG recordings near the time of facility admission and discharge. Coherence and power were computed, and structural imaging was obtained to assess stroke-related injury. Mixed-effects linear models and correlation analyses were employed to evaluate relationships between EEG measures and motor status, recovery, and injury. Results This work replicated key EEG biomarker findings from previous work. Individuals post-stroke (n = 30) depicted elevated delta coherence between bilateral motor cortices at the time of IRF admission that decreased over time, paralleling motor recovery and resembling coherence observed in controls (n = 17) by IRF discharge. Greater corticospinal tract injury and lesion volume were associated with greater delta and beta coherence and delta power, respectively, in leads overlying bilateral sensorimotor regions. Conclusions Replication of these findings in an independent cohort further substantiates resting-state low-frequency oscillatory activity as a marker of stroke-related injury and recovery. Collectively, these results support the validity of EEG-derived biomarkers in stroke and suggest that delta-band activity may represent a particularly relevant biomarker during early post-stroke motor recovery.