Spatiotemporal Phase Characteristics of Brain Alpha Wave Entrained to Alternating Red and Blue Flicker Stimuli

Abstract

We investigate spatiotemporal phase characteristics of the brain alpha waves in the entrainment to red, blue and alternating red/blue flicker stimuli. The alternating red/blue stimuli induce two distinct phase relationships between the alpha waves over the scalp dependent on subjects: 1) an antiphase relationship in approximately half the subjects in which the phases of the alpha waves are in the state of antiphase between the occipital and frontal lobes and 2) an in-phase relationship for the remaining subjects in which the phases of the alpha waves over the entire scalp are almost identical with only small phase differences. In the in-phase relationship, there occurs a phase difference approximately 90 deg between the occipital alpha wave and the alternating red/blue flicker stimuli, whereas the phase difference becomes almost zero in the antiphase relationship. The former anomalous phase response at the occipital lobe triggers the in-phase relationship over the entire scalp.