title: A P300 event-related potential brain-computer interface (BCI): the effects of matrix size and inter stimulus interval on performance.
abstract: We describe a study designed to assess properties of a P300 brain-computer interface (BCI). The BCI presents the user with a matrix containing letters and numbers. The user attends to a character to be communicated and the rows and columns of the matrix briefly intensify. Each time the attended character is intensified it serves as a rare event in an oddball sequence and it elicits a P300 response. The BCI works by detecting which character elicited a P300 response. We manipulated the size of the character matrix (either 3 x 3 or 6 x 6) and the duration of the inter stimulus interval (ISI) between intensifications (either 175 or 350 ms). Online accuracy was highest for the 3 x 3 matrix 175-ms ISI condition, while bit rate was highest for the 6 x 6 matrix 175-ms ISI condition. Average accuracy in the best condition for each subject was 88%. P300 amplitude was significantly greater for the attended stimulus and for the 6 x 6 matrix. This work demonstrates that matrix size and ISI are important variables to consider when optimizing a BCI system for individual users and that a P300-BCI can be used for effective communication.
authors.affiliation: Laboratory of Nervous System Disorders, Wadsworth Center, New York State Department of Health, E1001 Empire State Plaza, Albany, NY 12201, USA. esellers@wadsworth.org
authors.forename: Eric W
authors.initials: EW
authors.lastname: Sellers
authors.forename: Dean J
authors.initials: DJ
authors.lastname: Krusienski
authors.forename: Dennis J
authors.initials: DJ
authors.lastname: McFarland
authors.forename: Theresa M
authors.initials: TM
authors.lastname: Vaughan
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Wolpaw
mesh_terms: D000328:Adult; D001143:Arousal / Q000502:physiology*; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000503:physiopathology*; D003143:Communication Devices for People with Disabilities; D004569:Electroencephalography; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D030141:Feedback, Psychological; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016472:Motor Neuron Disease / Q000503:physiopathology / Q000534:rehabilitation; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D012858:Size Perception / Q000502:physiology*; D014584:User-Computer Interface