The effects of low-intensity narrow-band blue-light treatment compared to bright white-light treatment in seasonal affective disorder

Background: Ever since a new photoreceptor was discovered with a highest sensitivity to 470-490 nm blue light, it has been speculated that blue light has some advantages in the treatment of Seasonal Affective Disorder (SAD) over more traditional treatments. In this study we compared the effects of exposure to narrow-band blue light (BLUE) to those of broad-wavelength white light (BLT) in the treatment of SAD. Methods: In a 15-day design, 45 patients suffering from SAD completed 30-min sessions of light treatment on 5 consecutive days. 21 subjects received white-light treatment (BLT, broad-wavelength without UV, 10 000 lx, irradiance 31.7 W/m(2)), 24 subjects received narrow-band blue light (BLUE, 100 lx, irradiance 1.0 W/m(2)). All participants completed weekly questionnaires concerning mood and energy levels, and were also assessed by means of the SIGH-SAD, which is the primary outcome measure. Results: On day 15, SIGH-SAD ratings were significantly lower than on day 1 (BLT 73.2%, effect size 3.37; BLUE 67%, effect size 2.63), which outcomes were not statistically significant different between both conditions. Limitations: Small sample size. Conclusions: Light treatment is an effective treatment for SAD. The use of narrow-band blue light is equally effective as a treatment using bright white-light

Effects of Artificial Dawn and Morning Blue Light on Daytime Cognitive Performance, Well-being, Cortisol and Melatonin Levels.

Light exposure elicits numerous effects on human physiology and behavior, such as better cognitive performance and mood. Here we investigated the role of morning light exposure as a countermeasure for impaired cognitive performance and mood under sleep restriction (SR). Seventeen participants took part of a 48h laboratory protocol, during which three different light settings (separated by 2 wks) were administered each morning after two 6-h sleep restriction nights: a blue monochromatic LED (light-emitting diode) light condition (BL; 100 lux at 470 nm for 20 min) starting 2 h after scheduled wake-up time, a dawn-simulating light (DsL) starting 30 min before and ending 20 min after scheduled wake-up time (polychromatic light gradually increasing from 0 to 250 lux), and a dim light (DL) condition for 2 h beginning upon scheduled wake time (<8 lux). Cognitive tasks were performed every 2 h during scheduled wakefulness, and questionnaires were administered hourly to assess subjective sleepiness, mood, and well-being. Salivary melatonin and cortisol were collected throughout scheduled wakefulness in regular intervals, and the effects on melatonin were measured after only one light pulse. Following the first SR, analysis of the time course of cognitive performance during scheduled wakefulness indicated a decrease following DL, whereas it remained stable following BL and significantly improved after DsL. Cognitive performance levels during the second day after SR were not significantly affected by the different light conditions. However, after both SR nights, mood and well-being were significantly enhanced after exposure to morning DsL compared with DL and BL. Melatonin onset occurred earlier after morning BL exposure, than after morning DsL and DL, whereas salivary cortisol levels were higher at wake-up time after DsL compared with BL and DL. Our data indicate that exposure to an artificial morning dawn simulation light improves subjective well-being, mood, and cognitive performance, as compared with DL and BL, with minimal impact on circadian phase. Thus, DsL may provide an effective strategy for enhancing cognitive performance, well-being, and mood under mild sleep restriction

The melanopic sensitivity function accounts for melanopsin-driven responses in mice under diverse lighting conditions

\u3cp\u3eIn 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\u3csup\u3eZ\u3c/sup\u3eλ), 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\u3csup\u3eZ\u3c/sup\u3eλ function provides an accurate prediction of the sensitivity of melanopsin-dependent responses. We further show that V\u3csup\u3eZ\u3c/sup\u3eλ 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\u3csup\u3eZ\u3c/sup\u3eλ as an important new approach for light measurement with widespread practical utility.\u3c/p\u3

The melanopic sensitivity function accounts for melanopsin-driven responses in mice under diverse lighting conditions.

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)λ), 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)λ function provides an accurate prediction of the sensitivity of melanopsin-dependent responses. We further show that V(Z)λ 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)λ as an important new approach for light measurement with widespread practical utility

Dawn simulation light impacts on different cognitive domains under sleep restriction.

Chronic sleep restriction (SR) has deleterious effects on cognitive performance that can be counteracted by light exposure. However, it is still unknown if naturalistic light settings (dawn simulating light) can enhance daytime cognitive performance in a sustainable matter. Seventeen participants were enrolled in a 24-h balanced cross-over study, subsequent to SR (6-h of sleep). Two different light settings were administered each morning: a) dawn simulating light (DsL; polychromatic light gradually increasing from 0 to 250 lx during 30 min before wake-up time, with light around 250 lx for 20 min after wake-up time) and b) control dim light (DL; <8 lx). Cognitive tests were performed every 2 h during scheduled wakefulness and questionnaires were completed hourly to assess subjective mood. The analyses yielded a main effect of "light condition" for the motor tracking task, sustained attention to response task and a working memory task (visual 1 and 3-back task), as well as for the Simple Reaction Time Task, such that participants showed better task performance throughout the day after morning DsL exposure compared to DL. Furthermore, low performers benefited more from the light effects compared to high performers. Conversely, no significant influences from the DsL were found for the Psychomotor Vigilance Task and a contrary effect was observed for the digit symbol substitution test. No light effects were observed for subjective perception of sleepiness, mental effort, concentration and motivation. Our data indicate that short exposure to artificial morning light may significantly enhance cognitive performance in a domain-specific manner under conditions of mild SR

The melanopic sensitivity function accounts for OPN responses to spectrally modulated stimuli in rodless/coneless mice.

<p>(<b>A</b>) Spectral profile of stimuli that differ in irradiance but not melanopic illuminance (4-fold difference in total photons between ‘dim’ and ‘bright’), termed ‘melanopsin silent’. (<b>B</b>) Mean (± SEM) firing rate of 131 PON neurons to transitions between the two melanopsin silent stimuli. These transitions evoked no significant change in firing activity (paired t-test, P = 0.944). (<b>C</b>) Spectral profile of stimuli which differ substantially in melanopic illuminance (21-fold between dim and bright) but not total photons (<1% difference), termed ‘melanopsin active’. (<b>D</b>) Mean (± SEM) firing rate of PON neurons to transitions between the two melanopsin active stimuli. Transitions to the melanopsin ‘bright’ condition evoked a significant increase firing activity (paired t-test, P = 0.014, n = 131). Yellow bar in <b>C</b> & <b>D</b> indicates presentation of the ‘bright’ stimulus, with dim stimulus present at all other times.</p

The melanopic sensitivity function accounts for the spectral sensitivity of LGN responses in rodless/coneless mice.

<p>(<b>A</b>) Spectral profile of the 3 test stimuli and the melanopic sensitivity function (V^zλ: shaded area). (<b>B</b>) Example response of an <i>rd/rd cl</i> LGN neuron to the three test stimuli presented at a range of different irradiances (numbers above traces indicate log light intensity relative to the maximum achievable: 3.4 log m-lux). (<b>C</b>) Mean ± SEM responses to the three stimuli (and below in overlay) at maximum irradiance (n = 30 cells; each unit's response normalised to the largest change in firing rate across all stimuli). (<b>D–F</b>) Irradiance response relationship for <i>rd/rd cl</i> LGN responses to the three stimuli. A single curve best explains all the data (F-test) when irradiances are expressed in melanopic lux (<b>D</b>; P = 0.641), but not number of photons between 470–480 nm (<b>E</b>; P = 0.04), photopic lux (<b>F</b>; P = 0.001), total photons or total optical power (not shown).</p

The melanopic sensitivity function accounts for the spectral sensitivity of tonic LGN firing activity in mice with functional rods/cones.

<p>(<b>A</b>) Example response of an <i>Opn1mw^R</i> ‘sustained’ LGN neuron to the three test stimuli depicted in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053583#pone-0053583-g001" target="_blank">Fig. 1A</a> at a range of irradiances (numbers above traces indicate log light intensity relative to the maximum achievable-3.4 log m-lux). (<b>B</b>) Mean ± SEM response to the three stimuli (and below in overlay) at maximum irradiance (n = 46 cells; each unit's response normalised to the largest change in firing rate across all stimuli). (<b>C–E</b>) Irradiance response relationship for <i>Opn1mw^R</i> LGN sustained firing responses (20–30 s after stimulus onset) to the three stimuli. Sensitivity could be explained by a single linear function (F-test) when irradiances were expressed in melanopic lux (C; 0.432), but not in effective photon flux for L- or S-cones (<b>D</b> & <b>E</b>; P = 0.001 & 0.022 respectively).</p