Study on transient VEP-based brain-computer interface using non-direct gazed visual stimuli.

It is necessary for brain-computer interfaces (BCIs) to be non-offensive devices for daily use to improve the quality of life of users, especially for the motor disabled. Some BCIs which are based on steady-state visual evoked potentials (SSVEPs), however, are unpleasant because users have to gaze at high-speed blinking light as visual stimuli. Furthermore, these kinds of BCIs may not be used as universal devices because SSVEPs are not detectable by some users. Considering these facts, we propose a novel BCI using a non-direct gazing method based on transient VEPs. This interface uses a low-speed blinking lattice pattern as visual stimuli, and users gaze at other visual targets displayed on the right and the left sides of the stimuli. The gazing direction is determined by the waveform difference of transient VEPs detected when users gaze at either target. Compared with SSVEP-based BCIs, the proposed BCI is less annoying because it uses a low-speed blinking pattern as visual stimuli and users do not have to gaze at the stimuli directly. In addition, bipolar derivation could reduce unnecessary signals and the number of responses used for signal averaging to detect transient VEPs, which leads to shorter detection time of the VEPs providing this interface with acceptable speed as a BCI in terms of determining gazing direction. Experiments with 7 volunteer subjects showed more than an 85% accuracy rate in gaze direction judgments. The result suggests that the proposed BCI can be used as a substitute for SSVEP-based BCIs, especially for users in which SSVEPs are not detected.