《P300-Based Brainndash;Computer Interface》.pdfVIP

174 IEEE TRANSACTIONS ON REHABILITATION ENGINEERING, VOL. 8, NO. 2, JUNE 2000 The Mental Prosthesis: Assessing the Speed of a P300-Based Brain–Computer Interface Emanuel Donchin, Kevin M. Spencer, and Ranjith Wijesinghe Abstract—We describe a study designed to assess a brain–com- role the stimuli play in the subjects’ ongoing information puter interface (BCI), originally described by Farwell and Donchin processing. The endogenous components, on the other hand, [9] in 1988. The system utilizes the fact that the rare events in the are manifestation of processing activities that depend on the oddball paradigm elicit the P300 component of the event-related potential (ERP). The BCI presents the user with a matrix of 6 by 6 role of the stimuli within the task the subject is performing, cells, each containing one letter of the alphabet. The user focuses at- and on the interaction between any given event and the context tention on the cell containing the letter to be communicated while in which it is presented [5]. Structuring the manner in which the rows and the columns of the matrix are intensified. Each in- stimuli are presented, and controlling the interaction between tensification is an event in the oddball sequence, the row and the external events and the subject’s task can therefore control the column containing the attended cell are “rare” items and, there- fore, only these events elicit a P300. The computer thus detects variance in the endogenous components. the transmitted character by determining which row and which The P300 component of the ERP is one such endogenous column elicited the P300. We report an assessment, using a boot-