References of "Schmidt, Christina"
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See detailCircadian and homeostatic regulation of sleepiness and cognition and its neuronal underpinnings
Schmidt, Christina; Chellappa, Sarah Laxhmi ULg; Cajochen, Christian

in Garbarino, Sergio (Ed.) Sleepiness and Human Impact Assessment (in press)

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See detailTwo time pieces for sleep regulation: the circadian clock and the homeostatic hourglass
Cajochen, Christian; Schmidt, Christina; Chellappa, Sarah Laxhmi ULg

in Garbarino, Sergio (Ed.) Sleepiness and Human Impact Assessment (in press)

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See detailNeurophysiological basis of sleep and wakefulness
Chellappa, Sarah Laxhmi ULg; Schmidt, Christina; Cajochen, Christian

in Garbarino, Sergio (Ed.) Sleepiness and Human Impact Assessment (in press)

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See detailNeuroimaging, cognition, light and circadian rhythms
Gaggioni, Giulia ULg; Maquet, Pierre ULg; Schmidt, Christina et al

in Frontiers in Systems Neuroscience [=FNSYS] (2014)

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See detailEffects of Artificial Dawn and Morning Blue Light on Daytime Cognitive Performance, Well-being, Cortisol and Melatonin Levels.
Gabel, Virginie; Maire, Micheline; Reichert, Carolin F. et al

in Chronobiology International (2013), 30(8), 988-97

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 ... [more ▼]

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. [less ▲]

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See detailNeuroimaging of the interaction between circadian and homeostatic processes
Vandewalle, Gilles ULg; Schmidt, Christina

in Neuroimaging of Sleep and Sleep Disorders (2013)

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See detailHuman melatonin and alerting response to blue-enriched light depend on a polymorphism in the clock gene PER3.
Chellappa, Sarah Laxhmi ULg; Viola, Antoine U.; Schmidt, Christina et al

in Journal of Clinical Endocrinology and Metabolism (2012), 97(3), 433-7

CONTEXT: Light exposure, particularly at the short-wavelength range, triggers several nonvisual responses in humans. However, the extent to which the melatonin-suppressing and alerting effect of light ... [more ▼]

CONTEXT: Light exposure, particularly at the short-wavelength range, triggers several nonvisual responses in humans. However, the extent to which the melatonin-suppressing and alerting effect of light differs among individuals remains unknown. OBJECTIVE: Here we investigated whether blue-enriched polychromatic light impacts differentially on melatonin and subjective and objective alertness in healthy participants genotyped for the PERIOD3 (PER3) variable-number, tandem-repeat polymorphism. DESIGN, SETTING, AND PARTICIPANTS: Eighteen healthy young men homozygous for the PER3 polymorphism (PER3(5/5)and PER3(4/4)) underwent a balanced crossover design during the winter season, with light exposure to compact fluorescent lamps of 40 lux at 6500 K and at 2500 K during 2 h in the evening. RESULTS: In comparison to light at 2500 K, blue-enriched light at 6500 K induced a significant suppression of the evening rise in endogenous melatonin levels in PER3(5/5) individuals but not in PER3(4/4). Likewise, PER3(5/5) individuals exhibited a more pronounced alerting response to light at 6500 K than PER3(4/4) volunteers. Waking electroencephalographic activity in the theta range (5-7 Hz), a putative correlate of sleepiness, was drastically attenuated during light exposure at 6500 K in PER3(5/5) individuals as compared with PER3(4/4). CONCLUSIONS: We provide first evidence that humans homozygous for the PER3 5/5 allele are particularly sensitive to blue-enriched light, as indexed by the suppression of endogenous melatonin and waking theta activity. Light sensitivity in humans may be modulated by a clock gene polymorphism implicated in the sleep-wake regulation. [less ▲]

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See detailWhat keeps us awake? The role of clocks and hourglasses, light, and melatonin.
Cajochen, Christian; Chellappa, Sarah Laxhmi ULg; Schmidt, Christina

in International Review of Neurobiology (2010), 93

What is it that keeps us awake? Our assumption is that we consciously control our daily activities including sleep-wake behavior, as indicated by our need to make use of an alarm clock to wake up in the ... [more ▼]

What is it that keeps us awake? Our assumption is that we consciously control our daily activities including sleep-wake behavior, as indicated by our need to make use of an alarm clock to wake up in the morning in order to be at work on time. However, when we travel across multiple time zones or do shift work, we realize that our intentionally planned timings to rest and to remain active can interfere with an intrinsic regulation of sleep/wake cycles. This regulation is driven by a small region in the anterior hypothalamus of the brain, termed as the "circadian clock". This clock spontaneously synchronizes with the environmental light-dark cycle, thus enabling all organisms to adapt to and anticipate environmental changes. As a result, the circadian clock actively gates sleep and wakefulness to occur in synchrony with the light-dark cycles. Indeed, our internal clock is our best morning alarm clock, since it shuts off melatonin production and boosts cortisol secretion and heart rate 2-3h prior awakening from Morpheus arms. The main reason most of us still use artificial alarm clocks is that we habitually carry on a sleep depth and/or the sleep-wake timing is not ideally matched with our social/work schedule. This in turn can lead hourglass processes, as indexed by accumulated homeostatic sleep need over time, to strongly oppose the clock. To add to the complexity of our sleep and wakefulness behavior, light levels as well as exogenous melatonin can impinge on the clock, by means of their so-called zeitgeber (synchronizer) role or by acutely promoting sleep or wakefulness. Here we attempt to bring a holistic view on how light, melatonin, and the brain circuitry underlying circadian and homeostatic processes can modulate sleep and in particular alertness, by actively promoting awakening/arousal and sleep at certain times during the 24-h day. [less ▲]

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See detailNeurobiological bases of suicidality in major depression
Desseilles, Martin ULg; Scwartz, Sophie; Dang Vu, Thanh et al

in World Journal of Biological Psychiatry (2009), 9(Suppl. 1),

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See detailAbnormal neural filtering of irrelevant visual information in depression
Desseilles, Martin ULg; Balteau, Evelyne ULg; Sterpenich, Virginie et al

in NeuroImage (2009), 45(Suppl. 1),

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See detailChronotype-dependent performance modulation according to time of day : a functional neuroimaging approach
Schmidt, Christina; Collette, Fabienne ULg; Sterpenich, Virginie et al

in NeuroImage (2008), 41(Suppl. 1),

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See detailOwl or lark? Stroop-related cerebral activity is modulated by time of day and chronotype
Schmidt, Christina; Collette, Fabienne ULg; Sterpenich, Virginie et al

in Journal of Sleep Research (2008), 17(Suppl. 1),

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See detailNeural Correlates of a Non-Image-Forming Response to Light Exposure During the Daytime: a fMRI Study
Vandewalle, Gilles ULg; Balteau, Evelyne ULg; Moreau, V et al

in NeuroImage (2005), 26(Suppl. 1),

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See detailTime-of-day modulations of rCBF response in functional brain imaging studies: a meta-analysis
Schmidt, Christina; Dang Vu, Thanh; Orban, Pierre et al

in NeuroImage (2005), 26(Suppl. 1),

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