Daily and Seasonal Variation in the Spectral Composition of Light Exposure in Humans

Thorne, Helen C.; Jones, Kay; Peters, Stuart P.; Archer, Simon N.; Dijk, Derk‐Jan

doi:10.1080/07420520903044315

Cited by 121 publications

(114 citation statements)

References 40 publications

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“…Photoperiod is the most obvious factor associated with season and both the intensity and spectral composition of light to which people are exposed vary with season (36). Fig.…”

Section: Resultsmentioning

confidence: 99%

Seasonality in human cognitive brain responses

Meyer

Muto

Jaspar

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

102

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Daily variations in the environment have shaped life on Earth, with circadian cycles identified in most living organisms. Likewise, seasons correspond to annual environmental fluctuations to which organisms have adapted. However, little is known about seasonal variations in human brain physiology. We investigated annual rhythms of brain activity in a cross-sectional study of healthy young participants. They were maintained in an environment free of seasonal cues for 4.5 d, after which brain responses were assessed using functional magnetic resonance imaging (fMRI) while they performed two different cognitive tasks. Brain responses to both tasks varied significantly across seasons, but the phase of these annual rhythms was strikingly different, speaking for a complex impact of season on human brain function. For the sustained attention task, the maximum and minimum responses were located around summer and winter solstices, respectively, whereas for the working memory task, maximum and minimum responses were observed around autumn and spring equinoxes. These findings reveal previously unappreciated process-specific seasonality in human cognitive brain function that could contribute to intraindividual cognitive changes at specific times of year and changes in affective control in vulnerable populations.aily variations in the environment have constrained life on Earth, with circadian cycles identified in most living organisms, including in human physiology and cognition (1, 2). Seasonal variations in the environment have also triggered annual adaptations that are observed in the majority of species (for a review, see ref. 1). However, seasonal variations may seem more limited in our species or they are at least less recognized (3). Seasonality has indeed been reported for several physiological aspects including blood pressure (4), cholesterol (5), or calorie intake (6), with higher levels seen in winter or fall for food intake. Recently, seasonal variation in expression levels of a large set of genes has been reported for human white blood cells and adipose tissue (7). Furthermore, seasonal variations have been observed in several behavioral dimensions with peaks occurring at different time of year depending on the variable considered: conception (winter/ spring peak) and death [winter peak (8)] or violent suicide [spring/ summer peak (9)]. Mood has been the most extensively studied aspect of human behavior, with a large portion of the general population undergoing seasonal deteriorations in mood in winter, but these do not reach clinical threshold [e.g., subsyndromal seasonal affective disorder: up to 18% in North America (10)]. Furthermore, sparse studies suggest that, in addition to mood, other cognitive brain functions show annual variations in healthy individuals, but results are not consistent (11-13).Animal research suggests that the suprachiasmatic nucleus, site of the master circadian clock, is at least one of the sites mediating annual rhythmicity (14). The well-characterized circadian genetic machinery is...

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“…Photoperiod is the most obvious factor associated with season and both the intensity and spectral composition of light to which people are exposed vary with season (36). Fig.…”

Section: Resultsmentioning

confidence: 99%

Seasonality in human cognitive brain responses

Meyer

Muto

Jaspar

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

102

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“…In fact, recent reports showed that prolonged darkness or lack of light in rodents induces a depression-like state associated with structural brain changes (46), whereas complete blindness increases depression risk (47). Likewise, long-term changes in ambient light daily profile, such as light therapy, seem to restore normal mood regulation (1,2), and the spectral composition of light changes across the seasons (48). Interestingly, blue-enriched light seems to be equally effective as (visually) brighter white light in the treatment of SAD (49), and a polymorphism in the melanopsin gene has recently been associated with SAD (50).…”

Section: Discussionmentioning

confidence: 99%

Spectral quality of light modulates emotional brain responses in humans

Vandewalle

Schwartz

Grandjean

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

198

160

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Light therapy can be an effective treatment for mood disorders, suggesting that light is able to affect mood state in the long term. As a first step to understand this effect, we hypothesized that light might also acutely influence emotion and tested whether short exposures to light modulate emotional brain responses. During functional magnetic resonance imaging, 17 healthy volunteers listened to emotional and neutral vocal stimuli while being exposed to alternating 40-s periods of blue or green ambient light. Blue (relative to green) light increased responses to emotional stimuli in the voice area of the temporal cortex and in the hippocampus. During emotional processing, the functional connectivity between the voice area, the amygdala, and the hypothalamus was selectively enhanced in the context of blue illumination, which shows that responses to emotional stimulation in the hypothalamus and amygdala are influenced by both the decoding of vocal information in the voice area and the spectral quality of ambient light. These results demonstrate the acute influence of light and its spectral quality on emotional brain processing and identify a unique network merging affective and ambient light information.ight therapy is the treatment of choice for seasonal affective disorder (SAD) and is a promising treatment for other major affective disorders (1, 2), suggesting that light can modulate mood in the long term. To better understand this effect and because neural networks involved in emotional behavior have been implicated in mood disorders (3), we first assessed whether light can acutely influence normal brain emotional processing. Indeed, ambient light is known to regulate processes other than vision, such as hormone secretion, body temperature, and sleep, but also alertness and cognition (4-8). These nonclassical [also called "non-image-forming" or "nonvisual" response, but see recent findings (9)] responses to light are mediated through a nonclassical photoreception system, which is maximally sensitive to blue light (≈480 nm), as opposed to the classical photopic luminance visual pathways, maximally sensitive to green light (≈550 nm), and recruits the recently discovered intrinsically photosensitive retinal ganglion cells (ipRGC) expressing the photopigment melanopsin, in addition to rods and cones (7,(10)(11)(12)(13).The impact of ambient light is detected in the longer term through the regulation of circadian rhythms (4, 7), and the benefit of light therapy on mood has been proposed to be mediated through a long-term circadian effect (14). However, nonclassical responses to ambient light also result in acute physiological changes. For example, ambient light significantly modulates ongoing cognitive brain function, including attention, working memory, updating, and sensory processing, within a few tens of seconds (6,(15)(16)(17)(18). The amygdala, a core component of the emotional brain (3, 19) that receives sparse direct projections from ipRGC (20), is one of the brain areas acutely affected by changes in ambie...

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“…Similarly, the light-induced modulation of amygdala activity may correspond to one of the underlying reasons for the therapeutical property of light in mood disorders. Light therapy is the treatment of choice of seasonal affective disorder (SAD), and the relative contribution of blue light to overall natural light exposure is smaller during the winter than during the summer (Thorne et al, 2009). However, it is still uncertain as to whether the longterm effects of repeated exposures on mood as used in light therapy are related to the acute modulation of brain activity to tasks that do not involve emotion.…”

Section: Cerebral Correlates Of Light Impacts' On Cognitive Performancementioning

confidence: 99%

Can light make us bright? Effects of light on cognition and sleep

Chellappa

Gordijn

Cajochen

2011

Progress in Brain Research

120

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Light elicits robust nonvisual effects on numerous physiological and behavioral variables, such as the human sleep-wake cycle and cognitive performance. Light effects crucially rely on properties such as dose, duration, timing, and wavelength. Recently, the use of methods such as fMRI to assess light effects on nonvisual brain responses has revealed how light can optimize brain function during specific cognitive tasks, especially in tasks of sustained attention. In this chapter, we address two main issues: how light impinges on cognition via consolidation of human sleep-wake cycles; and how light directly impacts on sleep and cognition, in particular, in tasks of sustained attention. A thorough understanding of how light affects sleep and cognitive performance may help to improve light settings at home and at the workplace in order to improve well-being.

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Daily and Seasonal Variation in the Spectral Composition of Light Exposure in Humans

Cited by 121 publications

References 40 publications

Seasonality in human cognitive brain responses

Seasonality in human cognitive brain responses

Spectral quality of light modulates emotional brain responses in humans

Can light make us bright? Effects of light on cognition and sleep

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