Abstract
Electroencephalogram (EEG) can be synchronized with repetitive flicker stimuli with the stimulus frequency above 1 Hz. Such a syncronized EEG, which is referred to be as a steady-state visually evoked potential (SSVEP), is affected by mental concentration on the stimuli under eyes-closed condition. We investigated the amplitude change of the SSVEP in concentrating on flicker stimuli for a novel brain computer interface (BCI) based on the SSVEP with eyes closed for severely disabilities who were not able to control their eye movement to use conventional SSVEP-based BCIs. The grand means of the SSVEP amplitude ratio across 16 subjects were found to be reduced by more than 20 % with reference to the nonconcentration condition over the entire scalp when the subjects concentrated on the flicker stimuli under the conditions of flicker frequency of 10 Hz and stimulus intensity of 5 lx. Such desyncronization was limited to the occipital lobe and left parietal (O1, O2 and P3) under the condition of 14Hz and 5 lx. This result suggests the possibility of SSVEP-based BCI with eyes closed in terms of the mental focus.
