Dataset Information

Long-Term Reduction of Short-Wavelength Light Affects Sustained Attention and Visuospatial Working Memory With No Evidence for a Change in Circadian Rhythmicity.

ABSTRACT: The short wavelength, i.e., blue light, is crucial for non-image forming effects such as entrainment of the circadian system in humans. Moreover, many studies showed that blue light enhances alertness and performance in cognitive tasks. However, most scientific reports in this topic are based on experiments using short exposure to blue or blue-enriched light, and only a few focused on the effects of its reduced transmittance, especially in longer periods. The latter could potentially give insight into understanding if age-related sleep problems and cognitive decline are related to less amount of blue light reaching the retina, as the eyes' lenses yellow with age. In this study, we investigated the effects of prolonged blocking of blue light on cognitive functioning, in particular-sustained attention and visuospatial working memory, as well as on sleep, and melatonin and cortisol levels. A group of young, healthy participants was randomly allocated to either blue light blocking or control group. Depending on the group, participants wore amber contact lenses, reducing the transmittance of blue light by ?90% or regular contact lenses for a period of 4 weeks. No changes were observed for measurements related to sleep and sleep-wake rhythm. Dim light melatonin onset, evening levels of melatonin, and morning cortisol answer did not show any significant alterations during blue light (BL) blockade. The significant effects were revealed both for sustained attention and visuospatial memory, i.e., the longer blocking the blue light lasted, the greater decrease in performance observed. Additionally, the follow-up session conducted ?1 week after taking off the blue-blocking lenses revealed that in case of sustained attention, this detrimental effect of blocking BL is fully reversible. Our findings provide evidence that prolonged reduction of BL exposure directly affects human cognitive functioning regardless of circadian rhythmicity.

SUBMITTER: Domagalik A

PROVIDER: S-EPMC7348134 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Long-Term Reduction of Short-Wavelength Light Affects Sustained Attention and Visuospatial Working Memory With No Evidence for a Change in Circadian Rhythmicity.

Domagalik Aleksandra A Oginska Halszka H Beldzik Ewa E Fafrowicz Magdalena M Pokrywka Malgorzata M Chaniecki Piotr P Rekas Marek M Marek Tadeusz T

Frontiers in neuroscience 20200703

The short wavelength, i.e., blue light, is crucial for non-image forming effects such as entrainment of the circadian system in humans. Moreover, many studies showed that blue light enhances alertness and performance in cognitive tasks. However, most scientific reports in this topic are based on experiments using short exposure to blue or blue-enriched light, and only a few focused on the effects of its reduced transmittance, especially in longer periods. The latter could potentially give insigh ...[more]

PMID: 32719581

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Project description:In mammals, the suprachiasmatic nucleus (SCN) is the central pacemaker organizing circadian rhythms of behavior and physiology. At the cellular level, the mammalian clock consists of autoregulatory feedback loops involving a set of "clock genes," including the Cryptochrome (Cry) genes, Cry1 and Cry2. Experimental evidence suggests that Cry1 and Cry2 play distinct roles in circadian clock function. In mice, Cry1 is required for sustained circadian rhythms in dissociated SCN neurons or fibroblasts but not in organotypic SCN slices or at the behavioral level, whereas Cry2 is not required at any of these levels. It has been argued that coupling among SCN cellular oscillators compensates for clock gene defects to preserve oscillatory function. Here we test this hypothesis in Cry1(-/-) mice by first disrupting intercellular coupling in vivo using constant light (resulting in behavioral arrhythmicity) and then examining circadian clock gene expression in SCN slices at the single cell level. In this manner, we were able to test the role of intercellular coupling without drugs and while preserving tissue organization, avoiding the confounding influences of more invasive manipulations. Cry1(-/-) mice (as well as control Cry2(-/-) mice) bearing the PER2::LUC knock-in reporter were transferred from a standard light:dark cycle to constant bright light (~650 lux) to induce arrhythmic locomotor patterns. In SCN slices from these animals, we used bioluminescence imaging to monitor PER2::LUC expression in single cells. We show that SCN slices from rhythmic Cry1(-/-) and Cry2(-/-) mice had similarly high percentages of functional single-cell oscillators. In contrast, SCN slices from arrhythmic Cry1(-/-) mice had significantly fewer rhythmic cells than SCN slices from arrhythmic Cry2(-/-) mice. Thus, constant light in vivo disrupted intercellular SCN coupling to reveal a cell-autonomous circadian defect in Cry1(-/-) cells that is normally compensated by intercellular coupling in vivo.

Project description:Like neurons in the suprachiasmatic nucleus (SCN), the master circadian pacemaker in the brain, single fibroblasts can function as independent oscillators. In the SCN, synaptic and paracrine signaling among cells creates a robust, synchronized circadian oscillation, whereas there is no evidence for such integration in fibroblast cultures. However, interactions among single-cell fibroblast oscillators cannot be completely excluded, because fibroblasts were not isolated in previous work. In this study, we tested the autonomy of fibroblasts as single-cell circadian oscillators in high- and low-density culture, by single-cell imaging of cells from PER2::LUC circadian reporter mice. We found greatly reduced PER2::LUC rhythmicity in low-density cultures, which could result from lack of either constitutive or rhythmic paracrine signals from neighboring fibroblasts. To discriminate between these 2 possibilities, we mixed PER2::LUC wild-type (WT) cells with nonluminescent, nonrhythmic Bmal1-/- cells, so that density of rhythmic cells was low but overall cell density remained high. In this condition, WT cells showed clear rhythmicity similar to high-density cultures. We also mixed PER2::LUC WT cells with nonluminescent, long period Cry2-/- cells. In this condition, WT cells showed a period no different from cells cultured with rhythmic WT cells or nonrhythmic Bmal1-/- cells. In previous work, we found that low K? suppresses fibroblast rhythmicity, and we and others have found that either low K? or low Ca²? suppresses SCN rhythmicity. Therefore, we attempted to rescue rhythmicity of low-density fibroblasts with high K? (21 mM), high Ca²? (3.6 mM), or conditioned medium. Conditioned medium from high-density fibroblast cultures rescued rhythmicity of low-density cultures, whereas high K? or Ca²? medium did not consistently rescue rhythmicity. These data suggest that fibroblasts require paracrine signals from adjacent cells for normal expression of rhythmicity, but that these signals do not have to be rhythmic, and that rhythmic signals from other cells do not affect the intrinsic periods of fibroblasts.

Dataset Information

Long-Term Reduction of Short-Wavelength Light Affects Sustained Attention and Visuospatial Working Memory With No Evidence for a Change in Circadian Rhythmicity.

Publications

Long-Term Reduction of Short-Wavelength Light Affects Sustained Attention and Visuospatial Working Memory With No Evidence for a Change in Circadian Rhythmicity.

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