A motor imagery-based online interactive brain-controlled switch: Paradigm development and preliminary test

ObjectiveTo develop a practical motor imagery-based brain-controlled switch as functional as a real-world switch that is reliable with a minimal false positive operation rate and convenient for users without the need of attention to the switch during a ‘No Control’ state (when not to activate the switch).MethodsFour healthy volunteers were instructed to perform an intended motor imagery task following an external sync signal in order to turn on a virtual switch provided on a computer screen. No specific mental task was required during the ‘No Control’ state. The beta band event-related frequency power (event-related desynchronization or ERD) from a single EEG Laplacian channel was monitored online in real-time. The computer continuously monitored the relative ERD power level until it exceeded a pre-set threshold and turned on the virtual switch.ResultsSubject 1 achieved lowest average false positive rate of 0.4 ± 0.9% in a five-session online study during the entire ‘No Control’ state, whereby the subject required 6.8 ± 0.6 s of active urging time or total response time of 20.5 ± 1.9 s to perform repeated attempts in order to turn on the switch in the online interactive switch operation. The average false positive rate among four subjects was 0.8 ± 0.4% with average active urging time of 12.3 ± 4.4 s or average response time of 36.9 ± 13.0 s. Offline analysis from subject 2 shows that the overall performance from 10-fold cross-validation was 96.2% with 3 consecutive epoch averaging, which was further improved to 99.0% by computationally intensive methods.ConclusionsThe novel design of the brain-controlled switch using the ERD feature associated with motor imagery achieved minimal false positive rate with a reasonable active urging time or response time to activate the switch.SignificanceThe reliability and convenience of the developed brain-controlled switch may extend current brain–computer interface capacities in practical communication and control applications.