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Hirokuni Tagaya

Publications and source records attributed to Hirokuni Tagaya.

12 recordsLinked to original sources
PubMed2004

Time estimation during nocturnal sleep in human subjects.

It has been postulated that time estimation during nocturnal sleep in humans can be explained by an interval timing clock inside the brain. However, no systematic investigations have been carried out with respect to how the human brain perceives the passage of time during sleep. The brain mechanisms of over- or underestimation of time spent in sleep have not yet been clarified. Here, we carried out an experimental study in which 11 healthy volunteers participated in time estimation trials scheduled six times during 9 h nocturnal sleep periods, under carefully controlled conditions. The time estimation ratio (TER: a ratio of subjective passage of time to actual time interval) decreased significantly from the first to the sixth trial. Individual TER was positively correlated with slow wave sleep prior to the trial, while it was negatively correlated with REM sleep. Our results indicate that the human brain has an ability to estimate the passage of time during nocturnal sleep without referring to time cues, and that the accuracy of this function fluctuates from overestimation in the early hours of sleep to underestimation in the last hours of sleep.

Adolescent↗
PubMed2004

Deficits in long-term retention of learned motor skills in patients with cortical or subcortical degeneration.

We investigated the acquisition and long-term retention of new skills in patients with cortical (Alzheimer's disease, AD) and subcortical (progressive supranuclear palsy, PSP; Parkinson's disease, PD) degeneration. The motor skill task performance of the PD and PSP patients improved with training, but the improvement disappeared within a few months, whereas AD patients retained learned skills for 3-18 months. The results of our experiments show that subcortical dysfunction induces a retention deficit for newly learned motor skills. Our present study suggests that a normal striatum is necessary for the formation of long-lasting motor skills, and that the striatum plays an important role as a motor skill consolidation system.

Alzheimer Disease↗
PubMed2004

Acute cortisol administration promotes sleep intensity in man.

The neuronal mechanisms of sleep generation, in particular synchronization of brain activity in the process of non-rapid-eye movement (non-REM) sleep, has been elucidated in the past decade. A previous study of our group showed that acute administration of cortisol is known to increase slow-wave sleep and suppress rapid-eye movement (REM) sleep in man. To further elucidate the non-REM sleep-promoting effects of cortisol with respect to the synchronization of cortical activity, it is important to establish a sleep-state-specific quantitative EEG analysis. We therefore investigated the effects of repetitive injections of hydrocortisone on spectral composition of sleep EEG in 10 healthy male young volunteers. In addition, we performed high-frequency blood samplings to assess the relation between changes in the sleep EEG and sleep-associated secretion of growth hormone (GH). Cortisol administration resulted in a significant increase in highly synchronized EEG activity including delta and theta frequencies, according to a higher amount of slow-wave sleep. This effect predominated in the first few hours of night sleep. REM sleep was decreased, which appeared to be secondary to the lengthened first sleep cycle. The cortisol-induced stimulation of GH release did not occur in correspondence with the increased slow-wave activity. In view of the sleep impairing properties of corticotropin-releasing hormone (CRH) and the sleep-promoting function of GH-releasing hormone, it appears likely that a negative feedback inhibition of endogenous CRH was the key mechanism mediating the observed results. The cortisol-induced effects on sleep intensity and sleep-associated GH secretion appeared to be driven by different mechanisms.

Adult↗
PubMed2003

Circadian rhythms in humans' delta sleep electroencephalogram.

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 day and time-of-day as the repeated measures) revealed significant circadian rhythms in the powers of sigma and delta sleep EEGs, and in rectal temperature. These results obtained under conditions in which behavioral confounding factors of retiring and rising were experimentally minimized suggest that the circadian pacemaker contributes to determining the hours of day when one can sleep deeply.

Adult↗
PubMed2003

Circadian fluctuation of time perception in healthy human subjects.

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. Fourteen healthy young male adults participated in this study. Time perception sessions (TPS) were conducted 4 times at 0900, 1300, 1700 and 2100 h. The TPS consisted of five 10-s time production trials under five different conditions (control trial, those with reward, and 3 different dual-load working memory tasks). Subjective status was assessed using visual analogue scales (VAS). To verify a participant's vigilance state, an alpha attenuation coefficient (AAC) was calculated. Two-way repeated measures ANOVA for produced time revealed a significant main effect of session, but no effect of task or interaction. Although produced time was not correlated with AACs or VAS scores, there was a significant negative correlation between produced time and core body temperature. These results suggest that human short-term time perception may be more influenced by circadian rhythm than working memory load or psychophysiological status.

Adult↗
PubMed2003

[Somniloquy].

Explore the source record for details and available documents.

Adolescent↗
PubMed2002

Non-rapid-eye-movement sleep propensity after sleep deprivation in human subjects.

The circadian modulation of occurrence of non-rapid-eye-movement sleep (NREM) was investigated in 37 volunteers under dim-light conditions after 24-h total sleep deprivation using a 26-h 10/20-min ultra-short sleep-wake schedule. The propensity of NREM showed rapid increase followed by gradual decrease during the subjective day and nocturnal bouts during the subjective night coinciding with melatonin production. The mean propensity of NREM during the subjective day was smaller than that during the subjective night, even though the sleep debt due to the 24-h sleep deprivation would have enhanced NREM more strongly during the subjective day than that during the subjective night. These results suggest that the occurrence of NREM sleep is modulated by a circadian pacemaker.

Adult↗
PubMed2002

Larger phase angle between sleep propensity and melatonin rhythms in sighted humans with non-24-hour sleep-wake syndrome.

STUDY OBJECTIVES: This study was aimed to clarify phase angle between sleep propensity and the circadian pacemaker in patients with non-24-hour sleep-wake syndrome (Non-24). DESIGN AND SETTING: A case-control study was underaken. PARTICIPANTS: Sighted patient with Non-24 (4 males and 1 female, aged 16 to 39 y), and sex- and age-matched healthy controls (12 males and 3 females, aged 19 to 35 y) participated the study. MEASUREMENT AND INTERVENTION: Following an actigraphic assessment of the sleep-wake cycle in their homes, the participants entered an ultra-short sleep-wake schedule together with simultaneous measurement of dim light melatonin rhythm after 24-hour sleep deprivation. RESULTS: The period of the sleep-wake cycle observed at home was longer in the Non-24 patients (25.12 hours) than in the controls (24.02 hours, p<0.0001). The interval from sleep propensity (SP) onset to the melatonin midpoint (MLmid) was significantly shorter in the Non-24 patients than in the controls. The interval from the MLmid to the SP offset was significantly longer in the Non-24 patients than in the controls. CONCLUSIONS: It was postulated that Non-24 sufferers' delayed SP onset relative to the circadian pacemaker may accelerate the light-induced phase-delay, leading to sleep-wake cycle that is longer than 24 hours.

Adolescent↗
PubMed2002

Effects of nocturnal bright light on saliva melatonin, core body temperature and sleep propensity rhythms in human subjects.

Nine healthy male volunteers (mean age of 24) participated in two experimental sessions of random crossover design: a bright light (5000 lux for 5 h from 00:00 to 05:00 h) session and a dim light (10 lux for 5 h from 00:00 to 05:00 h) session. Subsequently participants entered an ultra-short sleep-wake schedule for 26 h, in which a sleep-wake cycle consisting of 10-min sleep EEG recording on a bed and 20-min resting awake on a semi-upright chair were repeated. Saliva melatonin level and core body temperature was measured throughout the experiment. Bright light significantly delayed rhythms of melatonin secretion (01:58 h), core body temperature (01:12 h) and sleep propensity (02:00 h), compared as dim light session. Significant positive correlation was found between bright light-induced phase change in core body temperature and that in sleep propensity rhythm. Light-induced melatonin suppression significantly positively correlated with the phase change in core body temperature and that in sleep propensity rhythm. Assuming that light-induced melatonin suppression represents an acute impact of light on the circadian pacemaker, our results suggest that such an impact may be directly reflected in phase changes of sleep propensity and core body temperature rhythms rather than in melatonin rhythm.

Adult↗
PubMed2002

Pergolide restores sleep maintenance but impairs sleep EEG synchronization in patients with restless legs syndrome.

BACKGROUND: The treatment with the long-acting dopamine D1/D2 receptor agonist pergolide has been proven as very effective in lowering the frequency of periodic leg movements (PLM) in patients with restless legs syndrome (RLS). To further investigate the influence of this potent dopaminergic drug on the microstructure of rapid eye movement (REM) and non-REM sleep EEG we established a quantitative analysis of the EEG data. METHODS: The study group consisted of 15 patients with primary RLS (mean age 57.1+/-10.1 years) who were a subgroup of patients within a double-blind randomized crossover treatment study with pergolide versus placebo. The polysomnographic recordings were analyzed visually and submitted to a quantitative EEG analysis (fast Fourier transformation). RESULTS: The pergolide treatment induced a significant reduction of the spectral power in the delta range (0.78-3.9 Hz; P<0.05; t-test) during SWS, as well as a significant reduction of PLMs. In addition, we observed a decrease in the sigma EEG activity (12.1-14.8 Hz; P<0.03) during non-REM sleep and stage 2 sleep. The visual sleep scoring revealed a significant increase in stage 2 sleep (P<0.005), whereas wakefulness was markedly diminished (P<0.001). The REM sleep parameters including the EEG power spectrum remained unchanged. CONCLUSIONS: The treatment with pergolide markedly improved the sleep quality in RLS patients but did not restore SWS including the spectral power in the lower frequencies. Our results suggest that the dopamine agonist pergolide interferes with the subcortical mechanisms regulating the process of EEG synchronization during non-REM sleep.

Clinical Trial↗
PubMed2002

Long-term rectal temperature measurements in a patient with menstrual-associated sleep disorder.

The international classification of sleep disorders has proposed menstrual-associated sleep disorder. However, few studies have investigated its pathophysiological mechanism. A 34-year-old woman complaining of insomnia in the late luteal phase underwent continuous rectal temperature measurements and simultaneous actigraphic monitoring for 146 days. The acrophase of rectal temperature rhythm was delayed in the luteal phase, compared with that in the follicular phase. Her bedtime and risetime did not differ across the menstrual cycle. These results suggest that her insomnia in the luteal phase may have been a consequence of desynchronization between her temperature rhythm and sleep phase in the luteal phase.

Adult↗