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STUDY OBJECTIVES There is a long-standing controversy surrounding the existence of dream experiences during non-rapid eye movement (NREM) sleep. Previous studies have not answered the question whether this "NREM dream" originates from the NREM sleep mechanism because the subject might simply be recalling experiences from the preceding rapid eye movement(More)
Evaluating individual circadian rhythm traits is crucial for understanding the human biological clock system. The present study reports characterization of physiological and molecular parameters in 13 healthy male subjects under a constant routine condition, where interfering factors were kept to minimum. We measured hormonal secretion levels and examined(More)
Working memory (WM) performance, which is an important factor for determining problem-solving and reasoning ability, has been firmly believed to be constant. However, recent findings have demonstrated that WM performance has the potential to be improved by repetitive training. Although various skills are reported to be improved by sleep, the beneficial(More)
Previous studies have reported that time perception in humans fluctuates over a 24-h period. Behavioral changes seem to affect human time perception, so that the fluctuation in human time perception may be the result of such changes due to self-determined activities. Recently, we carried out a study in which a healthy human cohort was asked to perform(More)
There are large inter-individual differences in pupil size and suppression of melatonin by exposure to light. It has been reported that melatonin suppression by exposure to light increases when pupils are pharmacologically dilated. However, the correlation between normal inter-individual difference in pupil size and melatonin suppression by exposure to(More)
Previous studies suggested that various psychophysiological factors have influences on human time perception. In particular, working memory loads, time of day, body temperature, and mood were known as important modifiers of time perception. The purpose of this study is to elucidate factors affecting the short-term time perception under controlled condition.(More)
Human short-time perception shows diurnal variation. In general, short-time perception fluctuates in parallel with circadian clock parameters, while diurnal variation seems to be modulated by sleep deprivation per se. Functional imaging studies have reported that short-time perception recruits a neural network that includes subcortical structures, as well(More)
Evaluation of circadian phenotypes is crucial for understanding the pathophysiology of diseases associated with disturbed biological rhythms such as circadian rhythm sleep disorders (CRSDs). We measured clock gene expression in fibroblasts from individual subjects and observed circadian rhythms in the cells (in vitro rhythms). Period length of the in vitro(More)
Eight healthy young male volunteers entered a 20-40 min ultrashort sleep-wake schedule for 78 h in the time-isolation facility. Rectal temperature was continuously recorded. Sleep electroencephalograms (EEGs) obtained during 20 min nap trials were stored in the computer and later analyzed by fast Fourier transform. A two-way repeated-measures ANOVA (with(More)
BACKGROUND Circadian rhythm sleep disorder, free-running type (FRT), is an intractable sleep disorder in which sleep and wake times progressively delay each day even in normal living environments. This disorder severely affects the social functioning of patients because of periodic nighttime insomnia, excessive daytime sleepiness, and a high rate of(More)