CF lamp with light at 6500K will promote an augmentation of subjective and objective alertness levels when compared to light at 2500K and at 3000K during and after 2-hour exposure to light in the evening.During 2-hour exposure to light in the evening, CF lamp with light at 6500K will attenuate the expression endogenous melatonin levels, in comparison to light at 2500K and at 3000K.Compact fluorescent (CF) lamps that provide correlated lamp colour temperature (CCT), that indicate the relative proportion of warm versus cool colours in a light source, are very often sold, because of the low energy consumption and governmental regulations to replace traditional incandescent bulbs.Ĭonsidering the mounting evidence that non-rod and non-cone photoreceptors might form the basis of the non-image forming photoreceptive pathway mediating both the circadian and direct effects of light, we hypothesized that the acute effect of light on melatonin, alertness, and cognitive performance is blue-shifted, such that CF lamp with 6500K (“cold light”) induce greater melatonin suppression and an enhanced alerting effect than CF lamp with 2500K (“warm light”) and incandescent light lamp of 3000K (“classic light”). Lamps and light-producing devices emitting exclusively or relatively more short-wavelength energy are now commercially available. In all the above mentioned studies, volunteers were tested under stringently controlled conditions, which are crucial for determining spectral sensitivity, but leave open the question of whether this sensitivity could be utilized in more practical scenarios to shift circadian rhythms, to alleviate jet lag and shift work symptoms, and to improve alertness and cognitive performance at the workplace and at house settings. Thus, besides phase shifting the human circadian clock scheduled exposure to light provides an effective tool for improving cognitive performance. Recent fMRI studies have demonstrated that daytime exposure to blue light, when compared to green or violet, is more effective in enhancing responses to a memory task in several cortical, thalamic and brainstem areas. Neurobehavioral responses triggered by light exposure encompass improved alertness and performance, , as indexed by specific cortical responses to cognitive tasks in Photon Emission Tomography and functional Magnetic Resonance Imaging (fMRI) techniques. Repercussions on human physiology include increased heart rate and core body temperature after blue (460 nm) but not after green light (550 nm) of equal photon density when administered in the evening, together with decreased electroencephalographic (EEG) slow-wave activity in the first cycle of non- rapid eye (NREM) sleep and shortened rapid eye movement (REM) sleep duration in the first two cycles. Furthermore, circadian phase shifts seem to be more sensitive to 460-nm light compared to 555-nm light at high irradiances.
Maximal response of this non-image-forming (NIF) system to light occurs between 446 and 483 nm for melatonin suppression. The non-visual effects of ocular light at short wavelengths strongly impinge on the human circadian timing system, , most probably via novel photoreceptors with the photopigment melanopsin. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.įunding: This research was supported by the Schweizerisches Bundesamt für Gesundheit ( ). Received: OctoAccepted: DecemPublished: January 26, 2011Ĭopyright: © 2011 Chellappa et al. Herzog, Ecole Polytechnique Federale de Lausanne, Switzerland
Citation: Chellappa SL, Steiner R, Blattner P, Oelhafen P, Götz T, Cajochen C (2011) Non-Visual Effects of Light on Melatonin, Alertness and Cognitive Performance: Can Blue-Enriched Light Keep Us Alert? PLoS ONE 6(1):Įditor: Michael H.
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