Frank A.J.L. Scheer

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We recently discovered that human activity possesses a complex temporal organization characterized by scale-invariant/self-similar fluctuations from seconds to approximately 4 h-(statistical properties of fluctuations remain the same at different time scales). Here, we show that scale-invariant activity patterns are essentially identical in humans and rats,(More)
There is considerable epidemiological evidence that shift work is associated with increased risk for obesity, diabetes, and cardiovascular disease, perhaps the result of physiologic maladaptation to chronically sleeping and eating at abnormal circadian times. To begin to understand underlying mechanisms, we determined the effects of such misalignment(More)
The circadian clock in the suprachiasmatic nucleus (SCN) is composed of thousands of oscillator neurons, each dependent on the cell-autonomous action of a defined set of circadian clock genes. Still, the major question remains how these individual oscillators are organized into a biological clock producing a coherent output able to time all the different(More)
Sleep inertia is the impaired cognitive performance immediately upon awakening, which decays over tens of minutes. This phenomenon has relevance to people who need to make important decisions soon after awakening, such as on-call emergency workers. Such awakenings can occur at varied times of day or night, so the objective of the study was to determine(More)
The suprachiasmatic nucleus (SCN) is the mammalian biological clock that generates the daily rhythms in physiology and behavior. Light can phase shift the rhythm of the SCN but can also acutely affect SCN activity and output, e.g., output to the pineal. Recently, multisynaptic SCN connections to other organs were also demonstrated. Moreover, they were shown(More)
Humans and animals demonstrate diurnal rhythms in physiology and behavior, which are generated by the circadian pacemaker, located in the supra-chiasmatic nucleus (SCN). The endogenous diurnal rhythm of the SCN is synchronized to the diurnal cycle most effectively by light. However, light also influences the SCN and its output instantaneously, as is(More)
Human expeditions to Mars will require adaptation to the 24.65-h Martian solar day-night cycle (sol), which is outside the range of entrainment of the human circadian pacemaker under lighting intensities to which astronauts are typically exposed. Failure to entrain the circadian time-keeping system to the desired rest-activity cycle disturbs sleep and(More)
The hypothalamus integrates information from the brain and the body; this activity is essential for survival of the individual (adaptation to the environment) and the species (reproduction). As a result, countless functions are regulated by neuroendocrine and autonomic hypothalamic processes in concert with the appropriate behaviour that is mediated by(More)
The mammalian biological clock, located in the suprachiasmatic nucleus (SCN), is crucial for circadian rhythms in physiology and behavior. However, equivocal findings have been reported on its role in the circadian regulation of body temperature. The goal of the present studies was to investigate the interaction between the SCN and environmental light in(More)
The morning shift in cardiac sympatho-vagal balance seems involved in the increased risk of cardiovascular incidents at that time. To investigate the contribution of the biological clock in autonomic cardiac control, we investigated the presence of a diurnal rhythm independent of external factors, and of a circadian phase-dependent effect of moderate light(More)