Influence of motor imagination on cortical activation during functional electrical stimulation

- In a motor imagery based BCI system to control FES, practicing imagery both before and during FES additionally increases intensity of event related desynchronisation throughout the whole period of electrical stimulation.
- Discontinuing to practice motor imagery following the onset of FES, reduces subsequent event-related desynchronisation.
- Motor imagery and FES produce event-related desynchronisation in similar frequency ranges.

ObjectiveMotor imagination (MI) and functional electrical stimulation (FES) can activate the sensory-motor cortex through efferent and afferent pathways respectively. Motor imagination can be used as a control strategy to activate FES through a brain-computer interface as the part of a rehabilitation therapy. It is believed that precise timing between the onset of MI and FES is important for strengthening the cortico-spinal pathways but it is not known whether prolonged MI during FES influences cortical response.MethodsElectroencephalogram was measured in ten able-bodied participants using MI strategy to control FES through a BCI system. Event related synchronisation/desynchronisation (ERS/ERD) over the sensory-motor cortex was analysed and compared in three paradigms: MI before FES, MI before and during FES and FES alone activated automatically.ResultsMI practiced both before and during FES produced strongest ERD. When MI only preceded FES it resulted in a weaker beta ERD during FES than when FES was activated automatically. Following termination of FES, beta ERD returns to the baseline level within 0.5 s while alpha ERD took longer than 1 s.ConclusionsWhen MI and FES are combined for rehabilitation purposes it is recommended that MI is practiced throughout FES activation period.SignificanceThe study is relevant for neurorehabilitation of movement.