Display Optimization in SSVEP BCIs

INTRODUCTION Brain – computer interface (BCI) systems allow people to send information without moving [1]. Some BCIs rely on the Steady State Visual Evoked Potential (SSVEP), a type of EEG activity that occurs when subjects focus attention on a stimulus that oscillates between about 5-40 Hz. Thus, the efficacy of an SSVEP BCI depends on how quickly and effectively it can distinguish SSVEP activity that reflects user attention from background noise. This depends on many factors, including EEG signal quality, task and display parameters, signal processing approaches, and user factors. SSVEP BCIs often utilize stimuli containing oscillating checkerboxes. Figure 1 below shows four examples of such displays [2][3][4][5]. In these BCIs, subjects direct attention to one of the oscillating checkerboxes to convey interest in a corresponding region. Thus, directing attention to the left checkerbox would move a game character, map, car, or cursor. It is also possible for subjects to focus attention on two targets, which could improve information throughput by increasing the number of commands available to a user [6].