Circadian and homeostatic modulation of cerebral correlates of vigilance under high and low sleep pressure
; ; Phillips, Christophe et al
Scientific conference (2015, September)Detailed reference viewed: 22 (1 ULg)
Circadian and sleep homeostatic regulation of cerebral correlates of working memory: time of day matters
; ; et al
Conference (2015, June)Detailed reference viewed: 7 (0 ULg)
Sleep-wake and time-of-day dependent modulations of working memory
; ; et al
Conference (2015)Detailed reference viewed: 12 (1 ULg)
Inter-individual differences in sleep-wake regulation: impact on attention-related cerebral correlates
Schmidt, Christina ; ; et al
Conference (2015)Detailed reference viewed: 22 (1 ULg)
Impact de l'horloge biologique et du cycle de veille-sommeil sur les capacités de vigilance.
Scientific conference (2015)Detailed reference viewed: 31 (4 ULg)
Impact de l’horloge biologique et du cycle de veille-sommeil sur les capacités cognitives
Scientific conference (2015)Detailed reference viewed: 24 (0 ULg)
How the brain copes to sustain attention at night-time: Impact of sleep pressure and genetic vulnerability to sleep loss
Scientific conference (2015)Detailed reference viewed: 14 (0 ULg)
Impact of circadian phase and prior wakefulness on cognition-related cerebral activity in humans.
Scientific conference (2015)Detailed reference viewed: 15 (0 ULg)
Dawn simulation light impacts on different cognitive domains under sleep restriction.
; ; et al
in Behavioural brain research (2015), 281
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 ... [more ▼]
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. [less ▲]Detailed reference viewed: 18 (0 ULg)
Pushing the Limits: Chronotype and Time of Day Modulate Working Memory-Dependent Cerebral Activity.
Schmidt, Christina ; Collette, Fabienne ; et al
in Frontiers in neurology (2015), 6
Morning-type individuals experience more difficulties to maintain optimal attentional performance throughout a normal waking day than evening types. However, time-of-day modulations may differ across ... [more ▼]
Morning-type individuals experience more difficulties to maintain optimal attentional performance throughout a normal waking day than evening types. However, time-of-day modulations may differ across cognitive domains. Using functional magnetic resonance imaging (fMRI), we investigated how chronotype and time of day interact with working memory at different levels of cognitive load/complexity in a N-back paradigm (N0-, N2-, and N3-back levels). Extreme morning- and evening-type individuals underwent two fMRI sessions during N-back performance, one 1.5 h (morning) and one 10.5 h (evening) after wake-up time scheduled according to their habitual sleep-wake preference. At the behavioral level, increasing working memory load resulted in lower accuracy while chronotype and time of day only exerted a marginal impact on performance. Analyses of neuroimaging data disclosed an interaction between chronotype, time of day, and the modulation of cerebral activity by working memory load in the thalamus and in the middle frontal cortex. In the subjective evening hours, evening types exhibited higher thalamic activity than morning types at the highest working memory load condition only (N3-back). Conversely, morning-type individuals exhibited higher activity than evening-type participants in the middle frontal gyrus during the morning session in the N3-back condition. Our data emphasize interindividual differences in time-of-day preferences and underlying cerebral activity, which should be taken into account when investigating vigilance state effects in task-related brain activity. These results support the hypothesis that higher task complexity leads to a chronotype-dependent increase in thalamic and frontal brain activity, permitting stabilization of working memory performance across the day. [less ▲]Detailed reference viewed: 43 (5 ULg)
Fighting Sleep at Night: Brain Correlates and Vulnerability to Sleep Loss.
; ; et al
in Annals of neurology (2015), 78(2), 235-47
OBJECTIVE: Even though wakefulness at night leads to profound performance deterioration and is regularly experienced by shift workers, its cerebral correlates remain virtually unexplored. METHODS: We ... [more ▼]
OBJECTIVE: Even though wakefulness at night leads to profound performance deterioration and is regularly experienced by shift workers, its cerebral correlates remain virtually unexplored. METHODS: We assessed brain activity in young healthy adults during a vigilant attention task under high and low sleep pressure during night-time, coinciding with strongest circadian sleep drive. We examined sleep-loss-related attentional vulnerability by considering a PERIOD3 polymorphism presumably impacting on sleep homeostasis. RESULTS: Our results link higher sleep-loss-related attentional vulnerability to cortical and subcortical deactivation patterns during slow reaction times (i.e., suboptimal vigilant attention). Concomitantly, thalamic regions were progressively less recruited with time-on-task and functionally less connected to task-related and arousal-promoting brain regions in those volunteers showing higher attentional instability in their behavior. The data further suggest that the latter is linked to shifts into a task-inactive default-mode network in between task-relevant stimulus occurrence. INTERPRETATION: We provide a multifaceted view on cerebral correlates of sleep loss at night and propose that genetic predisposition entails differential cerebral coping mechanisms, potentially compromising adequate performance during night work. [less ▲]Detailed reference viewed: 19 (1 ULg)
Dawn simulation light: a potential cardiac events protector.
; ; Chellappa, Sarah Laxhmi et al
in Sleep medicine (2015), 16(4), 457-61
OBJECTIVE/BACKGROUND: Major cardiovascular events frequently increase in the morning due to abrupt changes in the sympatho-vagal cardiac control during the transition from sleep to wakefulness. These ... [more ▼]
OBJECTIVE/BACKGROUND: Major cardiovascular events frequently increase in the morning due to abrupt changes in the sympatho-vagal cardiac control during the transition from sleep to wakefulness. These neural changes are translated into stepwise increases in cardiac functions, resulting in a potential cardiovascular stress. Here, we explored whether light can "optimize" heart rate and its neural control, by actively promoting a less steep transition from sleep to wakefulness, thus minimizing morning cardiovascular vulnerability. METHODS: Seventeen healthy young men were awakened 2-hours before their habitual wake-time. In a counterbalanced within-subject design, we applied a control condition (darkness during sleep and dim light during wakefulness) or dawn-simulation-light (DSL) starting 30-minutes before and ending 30-minutes after scheduled wake-up time. RESULTS: Our data reveal a significantly gradient reduction in heart rate during the transition from sleep to wakefulness, when applying DSL as compared to a control condition. Likewise, cardiac sympatho-vagal control smoothly increased throughout the 30-min sleep episode preceding scheduled wake-up under DSL and remained stable for the first 30-min of wakefulness. Interestingly, these effects were mostly driven by changes in the parasympathetic cardiac control. CONCLUSIONS: Our data demonstrate for the first time that a non-invasive strategy, as light exposure surrounding the wake-up process, can significantly reduce the deleterious sleep-to-wake evoked cardiac modulation in healthy young men awakened under conditions of increased sleep pressure. A translational approach of this light exposure, which closely resembles natural lighting conditions in the morning, may therefore act as a potential protector for cardiac vulnerability in the critical morning hours. [less ▲]Detailed reference viewed: 11 (0 ULg)
Blue blocker glasses as a countermeasure for alerting effects of evening light-emitting diode screen exposure in male teenagers.
; ; et al
in The Journal of adolescent health : official publication of the Society for Adolescent Medicine (2015), 56(1), 113-9
PURPOSE: Adolescents prefer sleep and wake times that are considerably delayed compared with younger children or adults. Concomitantly, multimedia use in the evening is prevalent among teenagers and ... [more ▼]
PURPOSE: Adolescents prefer sleep and wake times that are considerably delayed compared with younger children or adults. Concomitantly, multimedia use in the evening is prevalent among teenagers and involves light exposure, particularly in the blue-wavelength range to which the biological clock and its associated arousal promotion system is the most sensitive. We investigated whether the use of blue light-blocking glasses (BB) during the evening, while sitting in front of a light-emitting diode (LED) computer screen, favors sleep initiating mechanisms at the subjective, cognitive, and physiological level. METHODS: The ambulatory part of the study comprised 2 weeks during which the sleep-wake cycle, evening light exposure, and multimedia screen use were monitored in thirteen 15- to 17-year-old healthy male volunteers. BB or clear lenses as control glasses were worn in a counterbalanced crossover design for 1 week each, during the evening hours while using LED screens. Afterward, participants entered the laboratory and underwent an evening blue light-enriched LED screen exposure during which they wore the same glasses as during the preceding week. Salivary melatonin, subjective sleepiness, and vigilant attention were regularly assayed, and subsequent sleep was recorded by polysomnography. RESULTS: Compared with clear lenses, BB significantly attenuated LED-induced melatonin suppression in the evening and decreased vigilant attention and subjective alertness before bedtime. Visually scored sleep stages and behavioral measures collected the morning after were not modified. CONCLUSIONS: BB glasses may be useful in adolescents as a countermeasure for alerting effects induced by light exposure through LED screens and therefore potentially impede the negative effects modern lighting imposes on circadian physiology in the evening. [less ▲]Detailed reference viewed: 23 (2 ULg)
Individual differences in the non-image frroming effects of light on human sleep.
Chellappa, Sarah Laxhmi ; ; Schmidt, Christina et al
in Journal of Sleep Research (2014, September)Detailed reference viewed: 15 (1 ULg)
Blue blocker glasses as a countermeasure for alerting effects of evening LED - screen exposure in teenagers
; ; et al
in Journal of Sleep Research (2014, September), 23(Suppl.1), 178Detailed reference viewed: 21 (0 ULg)
Impact of sleep pressure, circadian phase and the ADA polymorphism on cerebral correlates underlying working memory performance
; ; et al
in Journal of Sleep Research (2014, September), 23(Suppl.1), 10Detailed reference viewed: 3 (0 ULg)
Sleep-loss related decrements in night-time vigilance performance: Cerebral correlates and the impact of genetic vulnerability
; ; et al
in Journal of Sleep Research (2014, September), 23(Suppl.1), 10Detailed reference viewed: 6 (0 ULg)
Age-dependent non-visual effects of a moderately bright light exposure during 40 hours of extended wakefulness.
; ; et al
in Journal of Sleep Research (2014, September), Volume 23(Suppl.1), 174-175Detailed reference viewed: 8 (0 ULg)
Light modulation of human sleep depends on a polymorphism in the clock gene Period3.
Chellappa, Sarah Laxhmi ; ; Schmidt, Christina et al
in Behavioural Brain Research (2014), 271
Non-image-forming (NIF) responses to light powerfully modulate human physiology. However, it remains scarcely understood how NIF responses to light modulate human sleep and its EEG hallmarks, and if there ... [more ▼]
Non-image-forming (NIF) responses to light powerfully modulate human physiology. However, it remains scarcely understood how NIF responses to light modulate human sleep and its EEG hallmarks, and if there are differences across individuals. Here we investigated NIF responses to light on sleep in individuals genotyped for the PERIOD3 (PER3) variable-number tandem-repeat (VNTR) polymorphism. Eighteen healthy young men (20-28 years; mean+/-SEM: 25.9+/-1.2) homozygous for the PER3 polymorphism were matched by age, body-mass index, and ethnicity. The study protocol comprised a balanced cross-over design during the winter, during which participants were exposed to either light of 40lx at 6500K (blue-enriched) or light at 2500K (non-blue enriched), during 2h in the evening. Compared to light at 2500K, light at 6500K induced a significant increase in all-night NREM sleep slow-wave activity (SWA: 1.0-4.5Hz) in the occipital cortex for PER3(5/5) individuals, but not for PER3(4/4) volunteers. Dynamics of SWA across sleep cycles revealed increased occipital NREM sleep SWA for virtuallyall sleep episode only for PER3(5/5) individuals. Furthermore, they experienced light at 6500K as significantly brighter. Intriguingly, this subjective perception of brightness significantly predicted their increased occipital SWA throughout the sleep episode. Our data indicate that humans homozygous for the PER3(5/5) allele are more sensitive to NIF light effects, as indexed by specific changes in sleep EEG activity. Ultimately, individual differences in NIF light responses on sleep may depend on a clock gene polymorphism involved in sleep-wake regulation. [less ▲]Detailed reference viewed: 26 (2 ULg)
Impact of circadian phase and prior wakefulness on cognition-related cerebral activity in humans
Schmidt, Christina ; ; et al
Conference (2014)Detailed reference viewed: 4 (0 ULg)