References of "Chellappa, Sarah Laxhmi"
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See detailSeasonality in human cognitive brain responses
Meyer, Christelle ULg; Muto, Vincenzo ULg; Jaspar, Mathieu ULg et al

in Proceedings of the National Academy of Sciences of the United States of America (2016)

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See detailAutomatic artifacts and arousals detection in whole-night sleep EEG recordings
Coppieters't Wallant, Dorothée ULg; Muto, Vincenzo ULg; Gaggioni, Giulia ULg et al

in Journal of Neuroscience Methods (2016), 258

In sleep electroencephalographic (EEG) signals, artifacts and arousals marking are usually part of the processing. This visual inspection by a human expert has two main drawbacks: it is very time ... [more ▼]

In sleep electroencephalographic (EEG) signals, artifacts and arousals marking are usually part of the processing. This visual inspection by a human expert has two main drawbacks: it is very time consuming and subjective. To detect artifacts and arousals in a reliable, systematic and reproducible automatic way, we developed an automatic detection based on time and frequency analysis with adapted thresholds derived from data themselves. The automatic detection performance is assessed using 5 statistic parameters, on 60 whole night sleep recordings coming from 35 healthy volunteers (male and female) aged between 19 and 26. The proposed approach proves its robustness against inter- and intra-, subjects and raters’ scorings, variability. The agreement with human raters is rated overall from substantial to excellent and provides a significantly more reliable method than between human raters. Existing methods detect only specific artifacts or only arousals, and/or these methods are validated on short episodes of sleep recordings, making it difficult to compare with our whole night results. The method works on a whole night recording and is fully automatic, reproducible, and reliable. Furthermore the implementation of the method will be made available online as open source code. [less ▲]

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See detailEyes Open on Sleep and Wake: In Vivo to In Silico Neural Networks
Vanvinckenroye, Amaury ULg; Vandewalle, Gilles ULg; Phillips, Christophe ULg et al

in Neural Plasticity (2015)

Functional and effective connectivity of cortical areas are essential for normal brain function under different behavioral states. Appropriate cortical activity during sleep and wakefulness is ensured by ... [more ▼]

Functional and effective connectivity of cortical areas are essential for normal brain function under different behavioral states. Appropriate cortical activity during sleep and wakefulness is ensured by the balanced activity of excitatory and inhibitory circuits. Ultimately, fast, millisecond cortical rhythmic oscillations shape cortical function in time and space. On a much longer time scale, brain function also depends on prior sleep-wake history and circadian processes. However,much remains to be established on how the brain operates at the neuronal level in humans during sleep and wakefulness. A key limitation of human neuroscience is the difficulty in isolating neuronal excitation/inhibition drive in vivo. Therefore, computational models are noninvasive approaches of choice to indirectly access hidden neuronal states. In this review, we present a physiologically driven in silico approach, Dynamic Causal Modelling (DCM), as a means to comprehend brain function under different experimental paradigms. Importantly, DCM has allowed for the understanding of how brain dynamics underscore brain plasticity, cognition, and different states of consciousness. In a broader perspective, noninvasive computational approaches, such as DCM, may help to puzzle out the spatial and temporal dynamics of human brain function at different behavioural states. [less ▲]

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See detailSeasonality in human cognitive brain responses.
Meyer, Christelle ULg; Muto, Vincenzo ULg; Jaspar, Mathieu ULg et al

Poster (2015, September 04)

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See detailHuman cortical excitability depends on time awake and circadian phase
Gaggioni, Giulia ULg; Ly, Julien; Chellappa, Sarah Laxhmi ULg et al

Poster (2015, January 27)

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See detailEvolution of Treatment and Investigative Approaches in Sleep Medicine
Ly, Julien; Chellappa, Sarah Laxhmi ULg; MAQUET, Pierre ULg

in Billiard, Michael (Ed.) Sleep Medicine: a comprehensive guide (2015)

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See detailDawn simulation light impacts on different cognitive domains under sleep restriction.
Gabel, Virginie; Maire, Micheline; Reichert, Carolin F. 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 ▲]

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See detailDawn simulation light: a potential cardiac events protector.
Viola, Antoine U.; Gabel, Virginie; Chellappa, Sarah Laxhmi ULg 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 ▲]

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See detailA finite-element reciprocity solution for EEG forward modeling with realistic individual head models
Ziegler, Erik ULg; Chellappa, Sarah Laxhmi ULg; Gaggioni, Giulia ULg et al

in NeuroImage (2014), 103

Highlights • Creates EEG forward models suitable for high-resolution source localization. • Automatic T1-based whole-head finite element meshing and leadfield computation. • Pipelines can incorporate ... [more ▼]

Highlights • Creates EEG forward models suitable for high-resolution source localization. • Automatic T1-based whole-head finite element meshing and leadfield computation. • Pipelines can incorporate conductivity tensors from diffusion-weighted images. • Open-source toolbox shared under a permissive software license. • Accuracy comparable to SimBio FEM and superior to OpenMEEG BEM solutions. [less ▲]

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See detailHuman cortical excitability depends on time spent awake and circadian phase
Ly, Julien ULg; Gaggioni, Giulia ULg; Chellappa, Sarah Laxhmi ULg et al

Scientific conference (2014, October 04)

At any point in time, human performance results from the interaction of two main factors: a circadian signal varying with the time of the day and the sleep need accrued throughout the preceding waking ... [more ▼]

At any point in time, human performance results from the interaction of two main factors: a circadian signal varying with the time of the day and the sleep need accrued throughout the preceding waking period. But what’s happen at the cortical cerebral level? We used a novel technique coupling transcranial magnetic stimulation with electroencephalography (TMS/EEG) to assess the influence of time spent awake and circadian phasis on human cortical excitability. Twenty-two healthy young men underwent 8 TMS/EEG sessions during a 28 hour sleep deprivation protocole. We found that cortical excitability depends on both time spent awake and circadian phasis. [less ▲]

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See detailAutomatic artifact detection for whole-night polysomnographic sleep recordings
Coppieters't Wallant, Dorothée ULg; Chellappa, Sarah Laxhmi ULg; Gaggioni, Giulia ULg et al

Poster (2014, September 17)

Detecting of bad channels and artifacts for whole-night polysomnographic recordings is very time consuming and tedious. We therefore developed an automatic procedure to automatize this job.

Detailed reference viewed: 49 (26 ULg)
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See detailHuman cortical excitability depends on time awake and circadian phase
Ly, Julien ULg; Chellappa, Sarah Laxhmi ULg; Gaggioni, Giulia ULg et al

Conference (2014, September 17)

At any point in time, human performance results from the interaction of two main factors: a circadian signal varying with the time of the day and the sleep need accrued throughout the preceding waking ... [more ▼]

At any point in time, human performance results from the interaction of two main factors: a circadian signal varying with the time of the day and the sleep need accrued throughout the preceding waking period. But what’s happen at the cortical cerebral level? We used a novel technique coupling transcranial magnetic stimulation with electroencephalography (TMS/EEG) to assess the influence of time spent awake and circadian phasis on human cortical excitability. Twenty-two healthy young men underwent 8 TMS/EEG sessions during a 28 hour sleep deprivation protocole. We found that cortical excitability depends on both time spent awake and circadian phasis. [less ▲]

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See detailHuman cortical excitability depends on time spent awake and circadian phase
Ly, Julien ULg; Chellappa, Sarah Laxhmi ULg; Gaggioni, Giulia ULg et al

Conference (2014, September 17)

At any point in time, human performance results from the interaction of two main factors: a circadian signal varying with the time of the day and the sleep need accrued throughout the preceding waking ... [more ▼]

At any point in time, human performance results from the interaction of two main factors: a circadian signal varying with the time of the day and the sleep need accrued throughout the preceding waking period. But what’s happen at the cortical cerebral level? We used a novel technique coupling transcranial magnetic stimulation with electroencephalography (TMS/EEG) to assess the influence of time spent awake and circadian phasis on human cortical excitability. Twenty-two healthy young men underwent 8 TMS/EEG sessions during a 28 hour sleep deprivation protocole. We found that cortical excitability depends on both time spent awake and circadian phasis. [less ▲]

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See detailIndividual differences in the non-image frroming effects of light on human sleep.
Chellappa, Sarah Laxhmi ULg; Viola, Antoine; Schmidt, Christina ULg et al

in Journal of Sleep Research (2014, September)

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See detailAutomatic biorythms description from actigraphic data
González y Viagas, Miguel ULg; Ly, Julien ULg; Gaggioni, Giulia ULg et al

Poster (2014, September)

Detailed reference viewed: 29 (8 ULg)