Relationship between event-related desynchronization and cortical excitability in healthy subjects and stroke patients

Objective: Relation between cortical excitability and magnitudes of event-related dysynchronizaton (ERD) has not been clarified. This study was investigated that relationshp between cortical excitability and ERD magnitudes in healthy subjects and stroke patients. Methods: Ten healthy subjects and four patients with stroke participated in this study. EEGs were recorded over the sensorimotor cortex (left hemisphere in healthy subjects; damaged hemisphere in stroke subjects) to calculate ERD during motor imagery,. Motor-evoked potential (MEP) induced by single-pulse transcranial magnetic stimulation over the primary motor cortex was recorded from the first dorsal interosseus (FDI) muscle at ERD magnitudes of 10% and 30%. Results: MEP significantly increased at 10% and 30% ERD (p < 0.01) than that during rest in healthy subjects. The 30% ERD condition showed significantly higher MEP than that at 10% ERD (p < 0.05). In stroke patients, MEP increased with ERD induced by motor imagery, but the change of MEP to ERD amplitude was critically different among the subject. Conclusion: ERD magnitude corresponds to corticospinal excitability increases in healthy subjects and patients with hemiplegic stroke. BCI based on motor imagery-induced ERD may be a potential rehabilitation strategy for patients with hemiplegic stroke.