A P300-based brain–computer interface for people with amyotrophic lateral sclerosis

Objective The current study evaluates the efficacy of a P300-based brain–computer interface (BCI) communication device for individuals with advanced ALS. Methods Participants attended to one cell of a N × N matrix while the N rows and N columns flashed randomly. Each cell of the matrix contained one character. Every flash of an attended character served as a rare event in an oddball sequence and elicited a P300 response. Classification coefficients derived using a stepwise linear discriminant function were applied to the data after each set of flashes. The character receiving the highest discriminant score was presented as feedback. Results In Phase I, six participants used a 6 × 6 matrix on 12 separate days with a mean rate of 1.2 selections/min and mean online and offline accuracies of 62% and 82%, respectively. In Phase II, four participants used either a 6 × 6 or a 7 × 7 matrix to produce novel and spontaneous statements with a mean online rate of 2.1 selections/min and online accuracy of 79%. The amplitude and latency of the P300 remained stable over 40 weeks. Conclusions Participants could communicate with the P300-based BCI and performance was stable over many months. Significance BCIs could provide an alternative communication and control technology in the daily lives of people severely disabled by ALS.