A transient VEP-based real-time 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 previously proposed a BCI using a non-direct gazing method based on transient VEPs. This interface used a low-speed blinking lattice pattern as visual stimuli and visual targets displayed on the right and the left sides of the stimuli. The gazing direction was determined by the waveform difference of transient VEPs detected when users gazed at either target. Compared with SSVEP-based BCLs, this BCI was less annoying because it used low-speed blinking visual stimuli, and it was not necessary for users to gaze at the stimuli directly. In this study, we propose an improved version of the BCI. Specifically, the gazing direction is determined in real time, and another gazing direction in which users gaze at a visual target displayed on the center of the screen is introduced while maintaining the annoyance-free advantage of the BCI. Experiments with 6 volunteer subjects showed an 84.2% accuracy rate in gazing direction judgments. The result suggests that the proposed BCI is more practical than the previous one because it can adapt to the change of gazing direction in real time.