Please use this identifier to cite or link to this item: https://doi.org/10.1126/scitranslmed.3000741
Title: Spectral responses of the human circadian system depend on the irradiance and duration of exposure to light
Authors: Gooley, J.J. 
Rajaratnam, S.M.W.
Brainard, G.C.
Kronauer, R.E.
Czeisler, C.A.
Lockley, S.W.
Issue Date: 2010
Source: Gooley, J.J., Rajaratnam, S.M.W., Brainard, G.C., Kronauer, R.E., Czeisler, C.A., Lockley, S.W. (2010). Spectral responses of the human circadian system depend on the irradiance and duration of exposure to light. Science Translational Medicine 2 (31) : 31ra33-. ScholarBank@NUS Repository. https://doi.org/10.1126/scitranslmed.3000741
Abstract: In humans, modulation of circadian rhythms by light is thought to be mediated primarily by melanopsin-containing retinal ganglion cells, not rods or cones. Melanopsin cells are intrinsically blue light-sensitive but also receive input from visual photoreceptors. We therefore tested in humans whether cone photoreceptors contribute to the regulation of circadian and neuroendocrine light responses. Dose-response curves for melatonin suppression and circadian phase resetting were constructed in subjects exposed to blue (460 nm) or green (555 nm) light near the onset of nocturnal melatonin secretion. At the beginning of the intervention, 555-nm light was equally effective as 460-nm light at suppressing melatonin, suggesting a significant contribution from the three-cone visual system (λmax = 555 nm). During the light exposure, however, the spectral sensitivity to 555-nm light decayed exponentially relative to 460-nm light. For phase-resetting responses, the effects of exposure to low-irradiance 555-nm light were too large relative to 460-nm light to be explained solely by the activation of melanopsin. Our findings suggest that cone photoreceptors contribute substantially to nonvisual responses at the beginning of a light exposure and at low irradiances, whereas melanopsin appears to be the primary circadian photopigment in response to long-duration light exposure and at high irradiances. These results suggest that light therapy for sleep disorders and other indications might be optimized by stimulating both photoreceptor systems.
Source Title: Science Translational Medicine
URI: http://scholarbank.nus.edu.sg/handle/10635/124687
ISSN: 19466234
DOI: 10.1126/scitranslmed.3000741
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