摘要:

The light/dark (L/D) cycle is a major synchronizer of human circadian rhythms. In the absence of a strong L/D cycle, synchrony with 24 hours can nevertheless be maintained in a socially structured environment, as shown in Polar regions (Broadwayet al. 1987) and by some blind subjects (Czeisleret al. 1995a). The relative contribution of other time cues to entrainment in dim light has not been fully explored. The present study investigated the behaviour of melatonin (assessed as 6‐sulphatoxymelatonin); rectal temperature; activity and sleep (actigraphy and logs) in constant dim light (L/L) with access to a digital clock. 6 normal healthy males were maintained as a group in partial temporal isolation with attenuated sound and ambient temperature for 21 days. All 6 subjects showed free‐running periodicity for 6‐sulphatoxymelatonin and 5/6 subjects for temperature, activity and sleep offset. The average period (tau) was 24.26±0.049, substantially shorter than in previous experiments with a self selected L/D cycle but similar to a recent study conducted in very dim light. One subject maintained a rigid sleep/wake cycle throughout whilst his 6‐sulphatoxymelatonin rhythm free‐ran. Total sleep time, from actigraph data, did not change but sleep efficiency decreased during the experiment. The subjects did not show group synchronization. These results confirm previous data indicating the importance of the L/D cycle in human entrainment and underline the lesser role of social cues and knowledge of clock time. This particular approach will permit the administration of timed medication to sighted humans under free‐runnin

ISSN:0962-1105    

DOI:10.1046/j.1365-2869.1996.d01-67.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

Melatonin is a hormone released during darkness under the control of the hypothalamic circadian pacemaker. It has been shown that melatonin is suppressed by light as a function of intensity, with low levels of illumination producing small effects and more intense light greater, but not complete inhibition. The studies which lead to these conclusions administered light subsequent to the secretion pattern being well established. Light as low as 250 lux administered during the normal onset of secretion can reduce melatonin to below detectable levels. The onset of melatonin secretion was delayed for at least an hour during 250 lux exposure and did not rise until termination of light exposure (two hours after control melatonin onset) with higher illumination (500, 1000 and 2500 lux). This tentatively indicates that duration of the inhibition is intensity dependent. It is suggested that the experimental paradigm used in the present study may be a more realistic representation of the effect of normal light exposure (both natural and artificial) on the circadian system, and that findings may be pertinent to the aetiology of certain sleep onset insomnias, which would include delayed sleep phase syndrome (DSPS) and adaptation to shift work.

ISSN:0962-1105    

DOI:10.1046/j.1365-2869.1996.00011.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

Parasympathetic Nervous System (PNS) activity increases while Sympathetic Nervous System (SNS) activity remains relatively stable from wakefulness to NREM sleep. However, it is not clear whether these changes are specifically associated with NREM sleep, or whether they anticipate sleep onset. The latter may occur if ANS activity was influenced by the circadian system. This issue was investigated by conducting spectral analysis of heart beat‐to‐beat intervals (Periodogram method), collected from 20 healthy male and female subjects at three different times across 24 h; in the morning, just prior to normal sleep onset time, and in slow‐wave sleep (SWS). Subjects were supine in all conditions and awake in the first two conditions. The high‐ and low‐frequency peaks, reflecting PNS and SNS activity, respectively, were expressed as proportions of the total power. PNS activity decreased significantly from the morning (0.22) to the presleep period (0.19), before it increased to its maximum during SWS (0.33). In contrast, SNS activity was similar in each of the three conditions (0.07, 0.06, and 0.05 for morning, presleep and SWS, respectively). Thus there do not appear to be changes in PNS activity in anticipation of sleep, as would be predicted on the basis of a circadian influence on the PNS. Instead the increased PNS activity appears to be sleep

ISSN:0962-1105    

DOI:10.1046/j.1365-2869.1996.00016.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

The aim of the present study was to assess the diurnal variation of sleep propensity by evaluating the temporal distribution of sleep onset latency (SOL) and REM‐ and slow‐wave sleep (SWS) parameters in systematically scheduled daytime naps for 12 young males. To reduce the effect of prior SWS on subsequent REM sleep, a double‐nap technique was used, i.e. two adjacent naps A and B, which were separated by a 10‐min break. Nap duration was adjusted in such a way that nap A allowed 30 min of sleep and nap B one complete NREM–REM cycle. EEG slow wave activity (SWA, power density from 0.5–4 Hz) was estimated from nap A and REM sleep parameters from nap B. The time span between 08.00 hours and 24.00 hours was covered by nine double‐naps at 2 h intervals. The order of the nap sessions was systematically varied within and across subjects. For each subject, the time between successive double‐nap recordings was at least three days. SOL was shortest in the time interval 12.00 hours to 16.00 hours and significantly longer between 20.00 hours and 24.00 hours. REM sleep duration and the percentage of sleep onset REM episodes decreased continuously from 08.00 hours to the interval 18.00–20.00 hours and increased thereafter, with a time course inversely related to the one of body temperature, which was also measured continuously. SWA showed a steady, threefold increase from 08.00 hours to 24.00 hours. The study offers new data on the diurnal variation of sleep propensity which seems to be a composite function of the drives for

ISSN:0962-1105    

DOI:10.1046/j.1365-2869.1996.00020.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

The aim of this experiment was to study the effects on sleep and temperature rhythms of a 6‐hour (h) phase advance of the sleep/wake cycle in healthy elderly subjects. Twenty‐five subjects (77–91 y.o.) lived in a time‐isolation apartment on an experimenter‐controlled routine for 15 days. The experiment started with five baseline days. The wake time on the 6th night was phase advanced by 6‐h and the routine for the remaining nine days was held constant to the new phase position. After the phase shift, temperature circadian rhythms showed rapid phase adjustment leading to a small (1.1 h) phase angle disturbance. Sleep efficiency decreased and showed little evidence of recovery back to baseline following the phase shift. The amount of wakefulness in the first two hours of sleep increased after the phase shift while no effect was found for the amount of wakefulness in the last two hours of sleep. The 6‐h phase shift did not change the percentages of REM and SWS. Early night sleep propensity appeared to be very sensitive to a small phase angle disturbance of the circadian oscillator in this healthy elderly sample. The phase angle disturbance induced in this study did not seem to be large enough to have a systematic effect on sleep propensity at the end of the night or on REM sleep parameters, suggesting that these variables are less sensitive to an altered phase relationship with the circadian oscillator than early night sleep propensity. These results indicate that there might be a variable phase tolerance for different sleep parameters in o

ISSN:0962-1105    

DOI:10.1046/j.1365-2869.1996.00015.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

It is hypothesized that tumour necrosis factor (TNF) is an endogenous substance involved in sleep responses occurring during bacterial infection. If this hypothesis is correct, then blocking endogenous TNF, using a TNF inhibitor, should attenuate the bacterial cell wall‐derived, muramyl dipeptide (MDP)‐induced sleep. To test this hypothesis, the effects of intracerebroventricular (i.c.v.) injection of a TNF inhibitor, a biologically active fragment of the soluble TNF 55 kDa receptor (TNFRF), on TNF‐α‐ and MDP‐induced sleep were determined in rabbits. I.c.v. injection of 250 ng human recombinant TNF‐α‐ or 150 pmol MDP increased non‐rapid‐eye‐movement sleep (NREMS), decreased rapid‐eye‐movement sleep (REMS), enhanced electroencephalogram slow‐wave activity (SWA) during NREMS and induced fever. Pretreatment of rabbits with 25 μg of the TNFRF significantly inhibited TNF‐α‐ and MDP‐induced sleep and fever responses. Finally, intravenously (i.v.) injected MDP enhanced NREMS, suppressed REMS, enhanced SWA, and induced fever; pretreatment of animals with the TNFRF injected centrally attenuated i.v. MDP‐induced sleep responses but not fever. These results suggest that the TNFRF acts as a TNF‐α antagonistin vivoand support the hypothesis that MDP‐induced s

ISSN:0962-1105    

DOI:10.1046/j.1365-2869.1996.d01-63.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

Growth hormone‐releasing hormone (GHRH) and somatostatin (SRIF) have been implicated as sleep factors. We studied how the hypothalamic SRIF/GHRH system is affected by possible feedback regulation resulting from REM sleep deprivation at the level of gene expression and how this is reflected in serum growth hormone (GH) content. Male rats were deprived of REM sleep on small platforms for 24 or 72 h, and one group was allowed a rebound sleep of 24 h after 72 h deprivation. Animals maintained on large platforms and animals taken directly from their home cages served as controls.In situhybridization was made from 20 μm cryosections through the periventricular, paraventricular and arcuate hypothalamic nuclei using oligonucleotide probes for GHRH and SRIF. The number of cells expressing SRIF or GHRH was counted. Serum GH was measured by means of radioimmunoassay in similarly treated rats. Fewer cells expressed GHRH in the paraventricular nucleus of animals subjected to 24 and 72 h of REM sleep deprivation than in home control animals. A similar trend was observed in the arcuate nucleus. The number of cells expressing SRIF was elevated in the arcuate nucleus after 24 h of REM sleep deprivation but not after 72 h. In the periventricular nucleus the number of cells expressing SRIF was higher after 72 h of deprivation when compared to expression in animals maintained on large platforms. Serum GH levels were decreased in animals maintained on either small or large platforms. It is concluded that the expression of the SRIF and GHRH genes is modulated by REM sleep deprivati

ISSN:0962-1105    

DOI:10.1046/j.1365-2869.1996.d01-66.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

The aim of this study was to evaluate the effects of nocturnal continuous positive airway pressure (CPAP) breathing on the emotional status and cognitive function in 20 patients with severe obstructive sleep apnoea (OSA) (mean±SD apnoea/hypopnoea index=67±16, mean overnight arterial oxygen saturation=83±10%). Psychological tests were performed before, after three, and after twelve months of CPAP treatment. At initial investigation, amongst cognitive functions, the most disturbed were concentration and recent memory. The majority of subjects demonstrated increased mental stress, depression, and anxiety. Anxiety correlated with AHI (r=0.68). Mental stress correlated with AHI (r=0.56) and deficiency of Stage 2 NREM sleep (r=−0.55). CPAP treatment resulted in significant improvement in cognitive function; concentration, recent verbal, visual and spatial memory were already seen at three months. No improvement in IQ and in emotional status after three months and one year of treatment was found. It is concluded that in patients with severe OSA CPAP treatment results in a significant early improvement in cognitive function but not in emotional st

ISSN:0962-1105    

DOI:10.1046/j.1365-2869.1996.d01-60.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

Previous attempts to investigate the relationship between sleepiness and performance for subjects with narcolepsy have been limited by both the ability of narcoleptic subjects to contain their sleepiness for brief testing periods and the potential lack of sensitivity of routine performance tasks to sleepiness induced changes. The present study developed a research protocol which allowed subjects with narcolepsy to express states of sleepiness and non sleepiness and to then compare the performance of subjects with narcolepsy to age, gender and IQ matched controls on tasks evaluating automatic, attentional and complex cognitive functioning. The results indicated that at high arousal subjects with narcolepsy performed as well as controls on automatic tasks suggesting that the capacity to perform for narcolepsy subjects is not restricted by physiological factors but is secondary to the effects of sleepiness. Comparison of both the within subject effects for narcolepsy subjects of the transition between high and low arousal states, and the between subject effects of low arousal for narcolepsy subjects compared to controls indicate that complex cognitive tasks are the most sensitive to arousal fluctuation. This study provides support for the subjective experiences of subjects with narcolepsy of diminished cognitive function associated with the disorder.

ISSN:0962-1105    

DOI:10.1046/j.1365-2869.1996.00018.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

ISSN:0962-1105    

DOI:10.1046/j.1365-2869.1996.d01-68.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY