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Spectral responses of the human circadian system depend on the irradiance and duration of exposure to light

Gooley, J.J., Rajaratnam, S.M.W., Brainard, G.C., Kronauer, R.E., Czeisler, C.A. and 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).

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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.

Item Type: Article
Authors :
Gooley, J.J.
Rajaratnam, S.M.W.
Brainard, G.C.
Kronauer, R.E.
Czeisler, C.A.
Date : 2010
DOI : 10.1126/scitranslmed.3000741
Uncontrolled Keywords : melanopsin, melatonin, adult, article, circadian rhythm, controlled study, evoked visual response, hormone inhibition, hormone release, human, human experiment, light exposure, normal human, photoreceptor, priority journal, radiation exposure, spectral sensitivity, visual stimulation, Adolescent, Adult, Circadian Rhythm, Dose-Response Relationship, Radiation, Humans, Light, Melatonin, Photoperiod, Phototherapy, Retina, Retinal Cone Photoreceptor Cells, Retinal Ganglion Cells, Rod Opsins, Young Adult
Depositing User : Clive Harris
Date Deposited : 17 Jun 2020 01:48
Last Modified : 17 Jun 2020 01:48

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