Effects of spectral distribution of light on the arousal level in humans

The effects of spectral distribution of light on the early component of contingent negative variation (CNV) and spontaneous electroencephalogram (EEG), indices generally used for the evaluation of arousal level, were investigated. Eight male volunteers (age range: 21-24 years) with normal color vision were exposed to three color temperature conditions (3000-3700K, 5000K, 6500K) coupled with three color rendering properties with flourescent lamps (Ra72-75, Ra88, Ra95-99). The CNV and spontaneous EEG were recorded for the last 8-min period of a total of 28-min exposure for each lighting condition. The arousal level was significantly higher under 6500K than 3000-3700K with Ra88 (furnished by a three-band-type fluorescent lamp). Although the early CNV potential and the relative energy of α waves were not significantly different between color temperature conditions with Ra72-75 and Ra95-99 (furnished by wide-band-type fluorescent lamps), the arousal level was significantly higher with Ra95-99 than Ra72-75 under similar lighting of 3000-3700K. The relative energy at long-wavelength-band of Ra95-99 was larger than that of Ra72-75. Further regression analysis on the relationships between the spectral distribution and arousal level was significant. These findings showed that the difference in spectral distribution rather than color temperatures and the band-type of lamps might influence the arousal level.