Effects of daytime exposures to short- and middle-wavelength lights on cortical activity during a cognitive task

This study aimed to assess the effects of light wavelength on human cortical activity during a cognitive task, by observing event-related potentials (ERPs). We measured ERPs when subjects perform an auditory oddball task under daytime exposures to short- and middle-wavelength lights. In the oddball task, a standard tone of 1 kHz and a target tone of 2 kHz were used. Subjects were instructed to press a button as soon as they heard the target tone. The ERP component that occurs approximately 300 ms after a stimulus onset (P300) was analyzed. The results showed that amplitude of P300 in the short-wavelength light condition was significantly larger than that in the middle-wavelength light condition approximately 10-20 min after the start of light exposure. It has been suggested that the amplitude of P300 reflects the amount of attentional resources for a given task. Therefore, the results obtained suggest that amount of attentional resource allocated to the oddball task is increased during exposure to the short-wavelength light in the daytime.