Diurnal physiology: core principles with application to the pathogenesis, diagnosis, prevention, and treatment of myocardial hypertrophy and failure.
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Neurobehavioral performance in young adults living on a 28-h day for 6 weeks.
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OBJECTIVES: Performance on many cognitive tasks varies with time awake and with circadian phase, and the forced desynchrony (FD) protocol can be used to separate these influences on performance. Some performance tasks show practice effects, whereas the Psychomotor Vigilance Task (PVT) has been reported not to show such effects. We aimed to compare performance on the PVT and on an addition test (ADD) across a 6-week FD study, to determine whether practice effects were present and to analyze the circadian and wake-dependent modulation of the 2 measures. DESIGN AND SETTING: A 47-day FD study conducted at the Brigham and Women's Hospital General Clinical Research Center. PARTICIPANTS: Eleven healthy adults (mean age: 24.4 years, 2 women). MEASUREMENTS AND RESULTS: For 2 baseline days and across 6 weeks of FD, we gave a test battery (ADD, PVT, self-rating of effort and performance) every 2 hours. During FD, there was a significant (P < 0.0001) improvement in ADD performance (more correct calculations completed), whereas PVT performance (mean reaction time, fastest 10% reaction times, lapses) significantly (P < 0.0001) declined week by week. Subjective ratings of PVT performance indicated that subjects felt their performance improved across the study (P < 0.0001), but their rating of whether they could have performed better with greater effort did not change across the study (P > 0.05). CONCLUSIONS: The decline in PVT performance suggests a cumulative effect of sleep loss across the 6-week study. Subjects did not accurately detect their declining PVT performance, and a motivational factor could not explain this decline. (+info)
Illuminating rationale and uses for light therapy.
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Light therapy is increasingly applied in a variety of sleep medicine and psychiatric conditions including circadian rhythm sleep disorders, seasonal affective disorder, and dementia. This article reviews the neural underpinnings of circadian neurobiology crucial for understanding the influence of light therapy on brain function, common mood and sleep disorders in which light therapy may be effectively used, and applications of light therapy in clinical practice. (+info)
Deregulation of growth factor, circadian clock, and cell cycle signaling in regenerating hepatocyte RXRalpha-deficient mouse livers.
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