1,721,103 research outputs found
Chronobiology, excessive daytime sleepiness and depression: Is there a link?
No full textThe complaint of excessive daytime sleepiness (EDS), commonly encountered in clinical practice, may arise from a variety of psychiatric disorders, most importantly depression. Even though EDS frequently leads depressed patients to seek medical assistance, it is commonly under-evaluated and under-diagnosed. Therefore, a comprehensive understanding and management of EDS is essential in the clinical assessment of depression. Within a theoretical framework, a chronobiological approach may shed new light on the complex interaction of EDS and depression. In this review, studies on EDS and depression are summarized and discussed within the context of circadian and sleep regulatory mechanisms. Furthermore, potential chronobiological therapeutic strategies are proposed to address some of the unmet needs in the treatment of EDS and depression
Ultradian and circadian modulation of dream recall: EEG correlates and age effects
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Circadian rhythm and epilepsy
No full textAdvances in diagnostic technology, including chronic intracranial EEG recordings, have confirmed the clinical observation of different temporal patterns of epileptic activity and seizure occurrence over a 24-h period. The rhythmic patterns in epileptic activity and seizure occurrence are probably related to vigilance states and circadian variation in excitatory and inhibitory balance. Core circadian genes BMAL1 and CLOCK, which code for transcription factors, have been shown to influence excitability and seizure threshold. Despite uncertainties about the relative contribution of vigilance states versus circadian rhythmicity, including circadian factors such as seizure timing improves sensitivity of seizure prediction algorithms in individual patients. Improved prediction of seizure occurrence opens the possibility for personalised antiepileptic drug-dosing regimens timed to particular phases of the circadian cycle to improve seizure control and to reduce side-effects and risks associated with seizures. Further studies are needed to clarify the pathways through which rhythmic patterns of epileptic activity are generated, because this might also inform future treatment options
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
What keeps us awake? : the role of clocks and hourglasses, light, and melatonin
Get PDFWhat 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
Effects of artificial dawn and morning blue light on daytime cognitive performance, well-being, cortisol and melatonin levels.
No full textLight 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 (58 lux). Cognitive tasks were performed every 2 h during
scheduled wakefulness, and questionnaires were administered hourly to assess subjective sleepiness, mood, and wellbeing. 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, wellbeing, and mood under mild sleep restriction
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dawn simulation light impacts on different cognitive domains under sleep restriction.
No full textChronic 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
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