Time courses of EEG power in the three light conditions. (a) Grand average time courses of EEG power in the alpha range for exposure to short- (circles) and long- (squares) wavelength lights, and darkness (triangles). Black and gray bars indicate the dark adaptation period and the light or dark exposure period, respectively. Error bars indicate ±1 SEM. Asterisks show significant differences compared with the darkness (*p < 0.05, **p < 0.01). Individual EEG power values in the alpha range in the (b) short-wavelength light, (c) long-wavelength light and (d) dark conditions. The same symbol indicates the values obtained from the same subject. (e) Grand average time courses of EEG power in the theta range.