EEG changes associated with mental focusing to flicker stimuli under eyes closed condition for SSVEP-based BCI

EEG synchronized with repetitive flicker stimuli, namely, steady-state visually evoked potential (SSVEP), can be affected by mental focusing to the stimuli under eyes-closed condition. The present study investigated dependence of the SSVEP amplitude on the mental focus to flicker stimuli in order to apply to the brain computer interface (BCI) based on the SSVEP with eyes closed for severely disabilities who are not able to control their eye movement to use conventional SSVEP-based BCI. The amplitude of the occipital SSVEP in 10 out of 11 healthy adults was found to be reduced by more than 30 % in the mental concentration to the flicker stimuli in comparison with that in the state of non-concentration under the conditions of flicker frequency of 10 Hz and stimulus intensity of 5 lx. This result suggests the possibility of SSVEP-based BCI with eyes closed in terms of the mental focus.