Abstract
The nonlinearity of the alpha wave in the human electroencephalogram (EEG) is one of the crucial properties for clarifying the underlying mechanism of the alpha wave. The present study examines effects of combination of two stimulus colors on the entrainment response of the alpha wave. Spatiotemporal behaviors of the alpha wave are investigated in terms of its amplitude and phase under the condition that red and blue flicker stimuli are temporally alternately applied. Two distinct responses are observed dependently on the subjects; 1) a phase reversal, in which the phase of the alpha wave in the occipital region is mostly reversed to that in the frontal region, and 2) a phase semi-locking, in which the phase difference between the frontal and occipital regions is almost less than 90 deg. On the contrary, the phase reversal is observed independently of the subjects when single-color (red, blue and white) stimuli are applied. The observation obtained suggests that the temporal alternation of red and blue stimuli affects the nonlinear response of the alpha wave.
