Response of Brain Waves to Periodic Flicker Stimuli - Entrainment and Steady-State Visually Evoked Potentials

Spatiotemporal phase dynamics of response of brain waves to periodic flicker stimuli are investigated to compare the response properties of the alpha waves with those of steady-state visually evoked potentials (SSVEPs). Under flicker stimuli the frequency of which is outside the range 8-13 Hz (outside the range of the alpha wave), the response of the brain wave, namely, the SSVEPs, constitutes the phase reversal between the frontal and occipital lobes as well as the spontaneous alpha wave for most of subjects. Under the flicker stimuli the frequency of which is in the range 8-13 Hz, the response of the brain wave, including the entrainment of the alpha wave as well as the SSVEPs, also shows the phase reversal. Spatial phase gradient of the SSVEPs is almost uniform from the frontal to occipital regions, which is also seen in the spontaneous alpha wave although the phase difference between the frontal and occipital lobes is varied complicatedly with time. These results suggest that the spatiotemporal dynamics of the SSVEPs and alpha wave are closely related to each other under the flicker stimuli. The underlying mechanism of the SSVEPs may be considered in the context of the entrainment of nonlinear oscillators