Simultaneous detection method of P300 event-related potentials and eye gaze point using multi-pseudorandom and flash stimulation for brain computer interface

A method for simultaneous detecting of P300 response and eye gaze point using visual evoked potentials (VEPs) elicited by multi-pseudorandom and flash stimuli was examined. Prototype system which would be a practical brain computer interface is established and evaluated. Visual stimuli consisted of six small squares (visual angle of 0.7 × 0.7 deg) surrounded by frames/a frame (2 × 2 deg). Squares were flashed with an interval of 180 ms to elicit event-related potential of P300, and luminance of each frame was modulated, based on pseudorandom binary sequences (PRBS) of 10.23 seconds. Six visual stimuli were simultaneously presented on the monitor and subjects were instructed to focus attention successively on an appointed square and EEG was recorded during this task. The cross correlation functions (kernels) of EEGs and each PRBS were calculated and used to determine the subject gazed target. Clear P300 and kernel response for target were simultaneously detected, indicating that this technique could be useful as a practical brain computer interface system.