Motor recovery following stroke is believed to necessitate alteration in functional connectivity between cortex and muscle. Cortico-muscular coherence has been proposed as a potential biomarker for post-stroke motor deficits, enabling a quantification of recovery, as well as potentially indicating the regions of cortex involved in recovery of function. We recorded simultaneous EEG and EMG during wrist extension from healthy participants and patients following ischaemic stroke, evaluating function at three time points post-stroke. EEG–EMG coherence increased over time, as wrist mobility recovered clinically, and by the final evaluation, coherence was higher in the patient group than in the healthy controls. Moreover, the cortical distribution differed between the groups, with coherence involving larger and more bilaterally scattered areas of cortex in the patients than in the healthy participants. The findings suggest that EEG–EMG coherence has the potential to serve as a biomarker for motor recovery and to provide information about the cortical regions that should be targeted in rehabilitation therapies based on real-time EEG.

Functional electrical stimulation (FES) is a standard rehabilitation approach applied by therapists to aid motor recovery in a paretic limb post-stroke. Information pertaining to the timing of a movement attempt can be obtained from changes in the power of oscillatory electrophysiological activity in motor cortical regions, derived from scalp electroencephalographic (EEG) recordings. The use of a brain-computer interface (BCI), to enable delivery of FES within a tight temporal window with a movement attempt detected in scalp EEG, is associated with greater motor recovery than conventional FES application in patients in the chronic phase post-stroke. We hypothesized that the heightened neural plasticity early post-stroke could further enhance motor recovery and that motor improvements would be accompanied by changes in the motor cortical sensorimotor rhythm after compared with before treatment. Here we assessed clinical outcome and changes in the sensorimotor rhythm in patients following subcortical stroke affecting the non-dominant hemisphere from a study comparing timing of FES delivery using a BCI, with a Sham group, receiving FES with no such temporal relationship. The BCI group showed greater clinical improvement following the treatment, particularly early post-stroke, and a greater decrease in beta oscillatory power and long-range temporal correlation over contralateral (ipsilesional) motor cortex. The electrophysiological changes are consistent with a reduction in compensatory processes and a transition towards a subcritical state when movement is triggered at the time of movement detection based on motor cortical oscillations.

ZusammenfassungEine Gehirn-Computer-Schnittstelle (BCI) in der Rehabilitation von Schlaganfallpatienten ermöglicht die Steuerung einer funktionellen Elektrostimulation (FES), um eine Muskelkontraktion in der gelähmten Extremität zum Zeitpunkt der Bewegungsintention durch Erkennung entsprechender Hirnsignale auszulösen. Es wird angenommen, dass eine genaue zeitliche Kohärenz zwischen Bewegungsintention und visuellem sowie propriozeptivem Feedback, ausgelöst durch eine reale Bewegung, neuroplastische Prozesse begünstigen und eine funktionelle Verbesserung der Parese bewirken kann. In dieser systematischen Übersichtsarbeit zu randomisierten kontrollierten Studien wurden die Datenbanken Pubmed, Scopus und Web of Science durchsucht und von 516 berücksichtigten Publikationen 13 ausgewählt, die auf 7 Studienpopulationen basierten. Ein direkter Vergleich der Studien ist durch Unterschiede im Studiendesign erschwert. Fünf Studien berichten von einer verbesserten motorischen Funktion in der BCI-FES-Gruppe, davon zeigen 3 signifikante Unterschiede zwischen der BCI-FES- und der Kontrollgruppe.