33 research outputs found
Spectral responses of the human circadian system depend on the irradiance and duration of exposure to light
10.1126/scitranslmed.3000741Science Translational Medicine23131ra33
Diurnal Spectral Sensitivity of the Acute Alerting Effects of Light
Study Objectives: Previous studies have demonstrated short-wavelength sensitivity for the acute alerting response to nocturnal light exposure.
We assessed daytime spectral sensitivity in alertness, performance, and waking electroencephalogram (EEG).
Design: Between-subjects (n = 8 per group).
Setting: Inpatient intensive physiologic monitoring unit.
Participants: Sixteen healthy young adults (mean age ± standard deviation = 23.8 ± 2.7 y).
Interventions: Equal photon density exposure (2.8 × 1013 photons/cm2/s) to monochromatic 460 nm (blue) or 555 nm (green) light for 6.5 h
centered in the middle of the 16-h episode of wakefulness during the biological day. Results were compared retrospectively to 16 individuals who
were administered the same light exposure during the night.
Measurements and Results: Daytime and nighttime 460-nm light exposure significantly improved auditory reaction time (P < 0.01 and P < 0.05,
respectively) and reduced attentional lapses (P < 0.05), and improved EEG correlates of alertness compared to 555-nm exposure. Whereas
subjective sleepiness ratings did not differ between the two spectral conditions during the daytime (P > 0.05), 460-nm light exposure at night
significantly reduced subjective sleepiness compared to 555-nm light exposure at night (P < 0.05). Moreover, nighttime 460-nm exposure improved
alertness to near-daytime levels.
Conclusions: The alerting effects of short-wavelength 460-nm light are mediated by counteracting both the circadian drive for sleepiness and
homeostatic sleep pressure at night, but only via reducing the effects of homeostatic sleep pressure during the day