Mechanisms associated with the alerting effects of light - Phase 2
Abstract
Light affects visual as well as non-visual pathways in ways that are not fully understood. The suppression of melatonin by light at night may mediate the positive effects of light on nocturnal performance and alertness. Recent work by our laboratory suggests that long-wavelength (red) light, which does not suppress melatonin, positively impacts objective and subjective alertness and certain types of performance both at night and during the daytime. Initially, the alerting effects of light were observed during the nighttime and after exposure to higher levels (>1000 lux at the cornea) of white light or lower (40 lux at the cornea) levels of short-wavelength (blue) light. It was suggested, based on these earlier studies, that the observed alerting effects of light were mediated by light~s ability to suppress nocturnal melatonin production. Melatonin is ahormone produced at night and under conditions of darkness. It is known as a ~darkness hormone~ because it is always produced during the biological night, and in diurnal species it signals that it is time to sleep. However, recent studies by our laboratory showed a strong alerting effect of long-wavelength (red) light, as measured by electroencephalogram (EEG), as well asself-reports of sleepiness during the daytime (when melatonin levels are low) and at night (when melatonin levels are high). Red light also reduced reaction times in certain types of performance tests. Therefore, light can have an impact on alertness and certain types of performance without affecting areas in the brain that are not associated with acute melatonin suppression.The mechanisms associated with the alerting effects of red light are unknown, however. Also unknown are the spectral and absolute sensitivities of this alerting effect of light. Unlike acute melatonin suppression, which has a peak spectral sensitivity at short wavelengths (close to 460 nm), the alerting effects of light seem to have a much broader spectral sensitivity. A technique that can be used to further elucidate mechanisms associated with the alerting effects of light is functional magnetic resonance imaging (fMRI). However, delivering a precise amount and specific spectra of light to the retina of subjects inside an MRI machine may pose a challenge. In Phase 1 of this proposal (submitted), we proposed to develop and test a lighting apparatus thatdelivers precise light stimulus to the retina of subjects who are placed inside an MRI machine. In Phase 2, proposed here, we will develop a dose response (absolute and spectral sensitivity) spanning from short- to long-wavelength lights. This will allow us to develop a spectral sensitivity function for the alerting stimulus of light. Once this function is developed in the laboratory, using fMRI scans, we will obtain a better understanding of the mechanisms in the brain that are associated with the alerting effects of light. To accomplish this research, we propose to collaborate with researchers at Cornell University. The resulting knowledge will have important implications for submariners, both on and off duty.On duty, red light can be effectively applied to increase subjective and objective alertness, as well as reaction time, without changing submariners~ circadian phase. Off duty, submariners will be able to fall asleep faster after being exposed to red light than to blue light, which might delay their sleep times. In a third phase of the study, we will work with researchers at the NavalSubmarine Medical Research Laboratory in Groton, CT, to obtain subjective assessment of these lighting schemes developed in Phase 2.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 03, 2017
- Source ID
- N000141712165
Entities
People
- Mariana Figueiro
Organizations
- Office of Naval Research
- Rensselaer Polytechnic Institute
- United States Navy