Binary brain computer interface in terms of steady state visual evoked potentials with eyes-closed by use of mental concentration on flicker stimuli

Brain computer interface (BCI) is expected to provide powerful help for disabled in communication with caregivers. Although many BCI systems have been developed, it is still difficult for severely disabled to use the BCIs due to strict limitations of motor function including facial and eye movement. The present study aimed at developing a novel binary class of BCI based on the steady-state visual evoked potential (SSVEP) in eyes-closed state. Amplitude change of the SSVEP elicited by mental concentration on periodic flicker stimuli was investigated for twelve normal adults aged 21–22 years old. Under the stimulus conditions of the flickering frequency of 10 Hz and the stimulus intensity of 5 lx, the SSVEP amplitude was significantly decreased over the wide region of the scalp when the subjects focused on the flicker stimuli. Such a response was repeated at least eight times associated with mental concentration on the stimuli. Improvement of the amplitude recovery in the relaxed state without mental concentration after the mental concentration may lead to establish the binary class of BCI with eyes-closed using mental concentration on the flicker stimuli.