The spectral composition of evening light and individual differences in the suppression of melatonin and delay of sleep in humans (original) (raw)
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Chronobiology International, 2010
The short-wavelength (blue) light sensitivity of human non-visual responses is recognised as being melanopsin-based. However, whether melanopsin is the sole factor in determining the efficacy of a polychromatic light source in driving non-visual responses remains to be established. Monochromatic (λ max 437, 479 and 532 nm) and polychromatic (colour temperature: 4000 K and 17000 K) light stimuli were photon matched for their predicted ability to stimulate melanopsin, and their capacity to affect nocturnal melatonin levels, auditory reaction time and subjective alertness and mood was assessed.
Melatonin suppression is exquisitely sensitive to light and primarily driven by melanopsin in humans
Journal of Pineal Research, 2019
Introduction: Light elicits a range of non-visual responses in humans. Driven predominantly by intrinsically photosensitive retinal ganglion cells (ipRGCs), but also by rods and/or cones, these responses include melatonin suppression. A sigmoidal relationship has been established between melatonin suppression and light intensity, however photoreceptoral involvement remains unclear. Methods and Results: In this study, we first modelled the relationships between alpha-opic illuminances and melatonin suppression using an extensive dataset by Brainard and colleagues. Our results show that 1) melatonin suppression is better predicted by melanopic illuminance compared to other alpha-opic illuminances, 2) melatonin suppression is predicted to occur at levels as low as ~1.5 melanopic lux (melanopsin-weighted irradiance 0.2 µW/cm²), 3) saturation occurs at 305 melanopic lux (melanopsin-weighted irradiance 36.6 µW/cm²). We then tested this melanopsin-weighted illuminance response model derived from Brainard and colleagues' data and show that it predicts equally well melatonin suppression data from our laboratory, although obtained using different intensities and exposure duration. Discussion: Together, our findings suggest that melatonin suppression by monochromatic lights is predominantly driven by melanopsin, and that it can be initiated at extremely low melanopic lux levels in experimental conditions. This emphasizes the concern of the nonvisual impacts of low light intensities in lighting design and light-emitting devices.
Measuring and using light in the melanopsin age
Trends in Neurosciences, 2014
Light is a potent stimulus for regulating circadian, hormonal, and behavioral systems. In addition, light therapy is effective for certain affective disorders, sleep problems, and circadian rhythm disruption. These biological and behavioral effects of light are influenced by a distinct photoreceptor in the eye, melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs), in addition to conventional rods and cones. We summarize the neurophysiology of this newly described sensory pathway and consider implications for the measurement, production, and application of light. A new light-measurement strategy taking account of the complex photoreceptive inputs to these non-visual responses is proposed for use by researchers, and simple suggestions for artificial/ architectural lighting are provided for regulatory authorities, lighting manufacturers, designers, and engineers.
Melanopsin Regulates Both Sleep-Promoting and Arousal-Promoting Responses to Light
PLoS biology, 2016
Light plays a critical role in the regulation of numerous aspects of physiology and behaviour, including the entrainment of circadian rhythms and the regulation of sleep. These responses involve melanopsin (OPN4)-expressing photosensitive retinal ganglion cells (pRGCs) in addition to rods and cones. Nocturnal light exposure in rodents has been shown to result in rapid sleep induction, in which melanopsin plays a key role. However, studies have also shown that light exposure can result in elevated corticosterone, a response that is not compatible with sleep. To investigate these contradictory findings and to dissect the relative contribution of pRGCs and rods/cones, we assessed the effects of light of different wavelengths on behaviourally defined sleep. Here, we show that blue light (470 nm) causes behavioural arousal, elevating corticosterone and delaying sleep onset. By contrast, green light (530 nm) produces rapid sleep induction. Compared to wildtype mice, these responses are al...
Journal of Biological Rhythms, 2011
Photoreception in the mammalian retina is not restricted to rods and cones but extends to a small number of intrinsically photosensitive retinal ganglion cells expressing the photopigment melanopsin. These mRGCs are especially important contributors to circadian entrainment, the pupil light reflex, and other so-called nonimage-forming (NIF) responses. The spectral sensitivity of melanopsin phototransduction has been addressed in several species by comparing responses to a range of monochromatic stimuli. The resultant action spectra match the predicted profile of an opsin:vitamin A–based photopigment (nomogram) with a peak sensitivity (λmax) around 480 nm. It would be most useful to be able to use this spectral sensitivity function to predict melanopsin’s sensitivity to broad-spectrum, including “white,” lights. However, evidence that melanopsin is a bistable pigment with an intrinsic light-dependent bleach recovery mechanism raises the possibility of a more complex relationship betw...
PLoS ONE, 2013
In addition to rods and cones, photoreception in mammals extends to a third retinal cell type expressing the photopigment melanopsin. The influences of this novel opsin are widespread, ranging from pupillary and circadian responses to brightness perception, yet established approaches to quantifying the biological effects of light do not adequately account for melanopsin sensitivity. We have recently proposed a novel metric, the melanopic sensitivity function (V Z l), to address this deficiency. Here, we further validate this new measure with a variety of tests based on potential barriers to its applicability identified in the literature or relating to obvious practical benefits. Using electrophysiogical approaches and pupillometry, initially in rodless+coneless mice, our data demonstrate that under a very wide range of different conditions (including switching between stimuli with highly divergent spectral content) the V Z l function provides an accurate prediction of the sensitivity of melanopsin-dependent responses. We further show that V Z l provides the best available description of the spectral sensitivity of at least one aspect of the visual response in mice with functional rods and cones: tonic firing activity in the lateral geniculate nuclei. Together, these data establish V Z l as an important new approach for light measurement with widespread practical utility.
Report Melanopsin-Based Brightness Discrimination in Mice and Humans
2012
Department of Ocular Biology and Therapeutics,University College London Institute of Ophthalmology,London EC1V 9EL, UKSummaryPhotoreception in the mammalian retina is not restricted torodsandconesbutextendstoasmallnumberofintrinsicallyphotoreceptive retinal ganglion cells (ipRGCs), expressingthe photopigment melanopsin [1–4]. ipRGCs are known tosupport various accessory visual functions including circa-dian photoentrainment and pupillary reflexes. However,despite anatomical and physiological evidence that theycontribute to the thalamocortical visual projection [5–7],no aspect of visual discrimination has been shown to relyupon ipRGCs. Based on their currently known roles,we hypothesized that ipRGCs may contribute to distin-guishing brightness. This percept is related to an object’sluminance—a photometric measure of light intensity rele-vant for cone photoreceptors. However, the perceivedbrightness of different sources is not always predicted bytheir respective luminance [8–12]. Here,...
Preliminary evidence for spectral opponency in the suppression of melatonin by light in humans
NeuroReport, 2004
Human adult males were exposed to light from blue light emitting diodes (18 lux; 29 mW/cm 2) and from clear mercury vapor lamps (450 lux; 170 mW/cm 2) during night-time experimental sessions. Both conditions suppressed nocturnal melatonin concentrations in blood plasma with the blue light more e¡ective than mercury at melatonin suppression. No additive model incorporating opsin photopigments either alone or in combination could explain the results, but a model incorporating an opponent mechanism was consistent with the present data as well as data from previously published studies. NeuroReport 15:313^316 c 2004 Lippincott Williams & Wilkins.
Preliminary evidence for a change in spectral sensitivity of the circadian system at night
Journal of Circadian Rhythms, 2005
Background It is well established that the absolute sensitivity of the suprachiasmatic nucleus to photic stimulation received through the retino-hypothalamic tract changes throughout the 24-hour day. It is also believed that a combination of classical photoreceptors (rods and cones) and melanopsin-containing retinal ganglion cells participate in circadian phototransduction, with a spectral sensitivity peaking between 440 and 500 nm. It is still unknown, however, whether the spectral sensitivity of the circadian system also changes throughout the solar day. Reported here is a new study that was designed to determine whether the spectral sensitivity of the circadian retinal phototransduction mechanism, measured through melatonin suppression and iris constriction, varies at night. Methods Human adult males were exposed to a high-pressure mercury lamp [450 lux (170 μW/cm2) at the cornea] and an array of blue light emitting diodes [18 lux (29 μW/cm2) at the cornea] during two nighttime experimental sessions. Both melatonin suppression and iris constriction were measured during and after a one-hour light exposure just after midnight and just before dawn. Results An increase in the percentage of melatonin suppression and an increase in pupil constriction for the mercury source relative to the blue light source at night were found, suggesting a temporal change in the contribution of photoreceptor mechanisms leading to melatonin suppression and, possibly, iris constriction by light in humans. Conclusion The preliminary data presented here suggest a change in the spectral sensitivity of circadian phototransduction mechanisms at two different times of the night. These findings are hypothesized to be the result of a change in the sensitivity of the melanopsin-expressing retinal ganglion cells to light during the night.