Wavelength-dependent effects of evening light exposure on sleep architecture and sleep EEG power density in men

Light strongly influences the circadian timing system in humans via non-image-forming photoreceptors in the retinal ganglion cells. Their spectral sensitivity is highest in the short-wavelength range of the visible light spectrum as demonstrated by melatonin suppression, circadian phase shifting, acute physiological responses, and subjective alertness. We tested the impact of short wavelength light (460 nm) on sleep EEG power spectra and sleep architecture. We hypothesized that its acute action on sleep is similar in magnitude to reported effects for polychromatic light at higher intensities and stronger than longer wavelength light (550 nm). The sleep EEGs of eight young men were analyzed after 2-h evening exposure to blue (460 nm) and green (550 nm) light of equal photon densities (2.8 x 10(13) photons x cm(-2) x s(-1)) and to dark (0 lux) under constant posture conditions. The time course of EEG slow-wave activity (SWA; 0.75-4.5 Hz) across sleep cycles after blue light at 460 nm was changed such that SWA was slightly reduced in the first and significantly increased during the third sleep cycle in parietal and occipital brain regions. Moreover, blue light significantly shortened rapid eye movement (REM) sleep duration during these two sleep cycles. Thus the light effects on the dynamics of SWA and REM sleep durations were blue shifted relative to the three-cone visual photopic system probably mediated by the circadian, non-image-forming visual system. Our results can be interpreted in terms of an induction of a circadian phase delay and/or repercussions of a stronger alerting effect after blue light, persisting into the sleep episode.     

Diaphragm long-term facilitation following acute intermittent hypoxia during wakefulness and sleep

Acute intermittent hypoxia (AIH) elicits a form of respiratory plasticity known as long-term facilitation (LTF). Here, we tested four hypotheses in unanesthetized, spontaneously breathing rats using radiotelemetry for EEG and diaphragm electromyography (Dia EMG) activity: 1) AIH induces LTF in Dia EMG activity; 2) diaphragm LTF (Dia LTF) is more robust during sleep vs. wakefulness; 3) AIH (or repetitive AIH) disrupts natural sleep-wake architecture; and 4) preconditioning with daily AIH (dAIH) for 7 days enhances Dia LTF. Sleep-wake states and Dia EMG were monitored before (60 min), during, and after (60 min) AIH (10, 5-min hypoxic episodes, 5-min normoxic intervals; n = 9), time control (continuous normoxia, n = 8), and AIH following dAIH preconditioning for 7 days (n = 7). Dia EMG activities during quiet wakefulness (QW), rapid eye movement (REM), and non-REM (NREM) sleep were analyzed and normalized to pre-AIH values in the same state. During NREM sleep, diaphragm amplitude (25.1 ± 4.6%), frequency (16.4 ± 4.7%), and minute diaphragm activity (amplitude × frequency; 45.2 ± 6.6%) increased above baseline 0-60 min post-AIH (all P < 0.05). This Dia LTF was less robust during QW and insignificant during REM sleep. dAIH preconditioning had no effect on LTF (P > 0.05). We conclude that 1) AIH induces Dia LTF during NREM sleep and wakefulness; 2) Dia LTF is greater in NREM sleep vs. QW and is abolished during REM sleep; 3) AIH and repetitive AIH disrupt natural sleep patterns; and 4) Dia LTF is unaffected by dAIH. The capacity for plasticity in spinal pump muscles during sleep and wakefulness suggests an important role in the neural control of breathing.     

Neurophysiological analysis of the effects of partial paradoxical sleep deprivation

A neurophysiological study was made of the effects of partial and complete paradoxial sleep deprivation by substituting episodes of active wakefulness for spells of paradoxical sleep (PS) of the same duration in the sleep-wake cycle. Neither accumulated need for paradoxical sleep (culminating in increased onset of PS during deprivation), PS rebound during the post-deprivation period, nor dissociation of the stages of paradoxical sleep resulting in their intervening individually at unaccustomed points in the sleep-wake cycle were observed during our experimental procedure. The phenomenon of self-deprivation, increased heart rate, eye movements, and pontogeniculooccipital (PGO) action potentials also failed to occur during the post-deprivation period. It is postulated that PS requirement and the need for periods of wakefulness stem from the same neurochemical alterations.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 20, No. 1, pp. 20–28, January–February, 1988.     

Spectral analysis of the heart rate variability in sleep

Spectral analysis of heart rate variability (HRV) during overnight polygraphic recording was performed in 11 healthy subjects. The total spectrum power, power of the VLF, LF and HF spectral bands and the mean R-R were evaluated. Compared to Stage 2 and Stage 4 non-REM sleep, the total spectrum power was significantly higher in REM sleep and its value gradually increased in the course of each REM cycle. The value of the VLF component (reflects slow regulatory mechanisms, e.g. the renin-angiotensin system, thermoregulation) was significantly higher in REM sleep than in Stage 2 and Stage 4 of non-REM sleep. The LF spectral component (linked to the sympathetic modulation) was significantly higher in REM sleep than in Stage 2 and Stage 4 non-REM sleep. On the contrary, a power of the HF spectral band (related to parasympathetic activity) was significantly higher in Stage 2 and Stage 4 non-REM than in REM sleep. The LF/HF ratio, which reflects the sympathovagal balance, had its maximal value during REM sleep and a minimal value in synchronous sleep. The LF/HF ratio significantly increased during 5-min segments of Stage 2 non-REM sleep immediately preceding REM sleep compared to 5-min segments of Stage 2 non-REM sleep preceding the slow-wave sleep. This expresses the sympathovagal shift to sympathetic predominance occurring before the onset of REM sleep. A significant lengthening of the R-R interval during subsequent cycles of Stage 2 non-REM sleep was documented, which is probably related to the shift of sympathovagal balance to a prevailing parasympathetic influence in the course of sleep. This finding corresponds to a trend of a gradual decrease of the LF/HF ratio in subsequent cycles of Stage 2 non-REM sleep.     

Athletes underestimate sleep quantity during daytime nap opportunities

ABSTRACT

This study examined the difference between athletes’ self-reported and objective sleep durations during two nap opportunities. Twelve well-trained male soccer players’ sleep durations were assessed using polysomnography and a self-report question during a 60- and 120-min nap opportunity. Participants underestimated sleep compared to objective sleep assessments for both the 60-min nap opportunity (p = 0.004) and 120-min nap opportunity (p = 0.001). Soccer players underestimated their sleep duration by approximately 10 min per hour of nap opportunity. It is yet to be determined if athletes are likely to underestimate sleep duration during their main nighttime sleep period.     

Effects of humid heat exposure in later sleep segments on sleep stages and body temperature in humans

This study sought to investigate the effects of humid heat exposure in later sleep segments on sleep stages and body temperature in humans. The subjects were eight healthy males, from whom informed consent had been obtained. The experiments were carried out under three different sets of conditions: a control climate [air temperature (Ta)=26°C, relative humidity (RH)=50%] (C); a humid heat climate (Ta=32°C, RH=80%) (H); and a humid heat exposure in later sleep segments (C for the first 3 h 45 min, followed by a 30-min transition to H, which was then maintained for the last 3 h 45 min) (C–H). Electroencephalogram, EOG, and mental electromyogram, rectal temperature (Tre), and skin temperature (Tsk) were continuously measured. The total amount of wakefulness was significantly increased in H compared to C–H or C. Compared to C, wakefulness in C–H and H was significantly increased during later sleep segments. Tre and mean Tsk were significantly higher in H than in C–H or C. In C–H, Tsk and Tre increased to levels equal to those observed in H after Ta and RH increase. Whole body sweat loss was significantly lower in C–H and C than in H. These results suggest that humid heat exposure in the later sleep segment reduces thermal load as compared to full-night humid heat exposure. In daily life, the use of air conditioning in the initial sleep hours can protect sleep and thermoregulation.     

Effect of color temperature of light sources on slow-wave sleep

In order to examine whether the spectral compositions of light source may affect sleep quality, sleep architecture under different color temperatures of light sources was evaluated. Seven healthy males were exposed to the light sources of different color temperatures (3000 K, 5000 K and 6700 K) for 6.5 h before sleep. The horizontal illuminance level was kept at 1000 lux. Subjects slept on a bed in near darkness (< 10 lux) after extinguishing the light, and polysomnograms recorded the sleep parameters. In the early phase of the sleep period, the amount of stage-4 sleep (S4-sleep) was significantly attenuated under the higher color temperature of 6700 K compared with the lower color temperature of 3000 K. Present findings suggest that light sources with higher color temperatures may affect sleep quality in a view that S4-sleep period is important for sleep quality.     

Time-of-day mediates the influences of extended wake and sleep restriction on simulated driving

Although a nonlinear time-of-day and prior wake interaction on performance has been well documented, two recent studies have aimed to incorporate the influences of sleep restriction into this paradigm. Through the use of sleep-restricted forced desynchrony protocols, both studies reported a time-of-day × sleep restriction interaction, as well as a time-of-day × prior wake × sleep dose three-way interaction. The current study aimed to investigate these interactions on simulated driving performance, a more complex task with ecological validity for the problem of fatigued driving. The driving performance of 41 male participants (mean?±?SD: 22.8 ±2.2 yrs) was assessed on a 10-min simulated driving task with the standard deviation of lateral position (SDLAT) measured. Using a between-group design, participants were subjected to either a control condition of 9.33 h of sleep/18.66 h of wake, a moderate sleep-restriction (SR) condition of 7 h of sleep/21 h of wake, or a severe SR condition of 4.66 h of sleep/23.33 h of wake. In each condition, participants were tested at 2.5-h intervals after waking across 7 × 28-h d of forced desynchrony. Driving sessions occurred at nine doses of prior wake, within six divisions of the circadian cycle based on core body temperature (CBT). Mixed-models analyses of variance (ANOVAs) revealed significant main effects of time-of-day, prior wake, sleep debt, and sleep dose on SDLAT. Additionally, significant two-way interactions of time-of-day × prior wake and time-of-day × sleep debt, as well as significant three-way interactions of time-of-day × prior wake × sleep debt and time-of-day × sleep debt × sleep dose were observed. Although limitations such as the presence of practice effects and large standard errors are noted, the study concludes with three findings. The main effects demonstrate that extending wake, reducing sleep, and driving at poor times of day all significantly impair driving performance at an individual level. In addition to this, combining either extended wake or a sleep debt with the early morning hours greatly decreases driving performance. Finally, operating under the influence of a reduced sleep dose can greatly decrease performance at all times of the day.     

GABA-A and GABA-B receptors in the cuneate nucleus of the rat in vivo

Electric stimulation of the rat forepaw evokes a negative potential (N-wave) at the ipsilateral cuneate nucleus. The responses of the N-wave to microiontophoretically applied GABA agonists and antagonists have been studied. Applications of GABA-A agonists (3-amino-propanesulfonic acid and muscimol) reduce the amplitude of the N-wave. This effect decreases during prolonged application, suggesting a desensitization of GABA-A receptors. In addition the effect of muscimol is reduced by (-)-bicuculline methiodide. Baclofen (a GABA-B agonist) also depresses the N-wave but its action lasts longer, is less reversible, shows no desensitization and is not blocked by (-)-bicuculline methiodide. The different responses of the N-wave to GABA-A and GABA-B agonists are compatible with the existence of different types of functional receptors for them in the cuneate nucleus of the rat. The receptors activated by muscimol (GABA-A) are clearly not the same as the ones activated by baclofen (conceivably GABA-B).     

Nitric oxide production in the basal forebrain is required for recovery sleep

Sleep homeostasis is the process by which recovery sleep is generated by prolonged wakefulness. The molecular mechanisms underlying this important phenomenon are poorly understood. Here, we assessed the role of the intercellular gaseous signaling agent NO in sleep homeostasis. We measured the concentration of nitrite and nitrate, indicative of NO production, in the basal forebrain (BF) of rats during sleep deprivation (SD), and found the level increased by 100 +/- 51%. To test whether an increase in NO production might play a causal role in recovery sleep, we administered compounds into the BF that increase or decrease concentrations of NO. Infusion of either a NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, or a NO synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME), completely abolished non-rapid eye movement (NREM) recovery sleep. Infusion of a NO donor, (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2diolate (DETA/NO), produced an increase in NREM that closely resembled NREM recovery after prolonged wakefulness. The effects of inhibition of NO synthesis and the pharmacological induction of sleep were effective only in the BF area. Indicators of energy metabolism, adenosine, lactate and pyruvate increased during prolonged wakefulness and DETA/NO infusion, whereas L-NAME infusion during SD prevented the increases. We conclude that an increase in NO production in the BF is a causal event in the induction of recovery sleep.     

Slow-wave sleep in daytime and nocturnal sleep: an estimate of the time course of "Process S"

Daan et al. (1984) have proposed that sleep and wakefulness are regulated, in part, by a "Process S" that increases during wakefulness and declines during sleep. Data derived from several studies were taken to determine the time course of Process S during both wakefulness and sleep. As required by the model, slow-wave-sleep (SWS; an index of Process S) was found to increase exponentially as a function of prior wake time (equation 1) and to decline exponentially as a function of time asleep (equation 2). The equations accounted for 91% and 96% of the variance, respectively. In addition, equation 1 accurately predicted the amount the amount of SWS in the first hour of nocturnal sleep.     

Principal components of electroencephalographic spectrum as markers of opponent processes underlying ultradian sleep cycles

Sleep-wake regulation involves reciprocal interactions between sleep- and wake-promoting processes that inhibit one another. To uncover the signatures of the opponent processes underlying ultradian sleep cycles, principal component analysis was performed on the sets of 16 single-Hz log-transformed electroencephalographic (EEG) power densities (1-16?Hz frequency range). Data were collected during unrestricted night sleep followed by 9 20-min naps (14 women aged 17-55 yrs) and during 12 20-min naps after either restriction or deprivation of sleep (9 males and 9 males, respectively, aged 18-22 yrs). It was found that any subset of power spectra could be reduced to the invariant four-principal component structure. The time courses of scores on these four components might be interpreted as the spectral EEG markers of the kinetics of two pairs of opponent chronoregulatory processes. In a sequence of ultradian sleep cycles, the 1st and 2nd components represent the alternations between competing drives for sleep and wakefulness, respectively, whereas the 3rd and 4th components reflect the alternations between light and deep sleep, respectively. The results suggest that principal component structuring of EEG spectrum can be employed for derivation of the parameters of the quantitative models conceptualizing the three major aspects of sleep-wake regulation—homeostatic, circadian, and ultradian processes.     

Circadian gene variants influence sleep and the sleep electroencephalogram in humans

The sleep electroencephalogram (EEG) is highly heritable in humans and yet little is known about the genetic basis of inter-individual differences in sleep architecture. The aim of this study was to identify associations between candidate circadian gene variants and the polysomnogram, recorded under highly controlled laboratory conditions during a baseline, overnight, 8 h sleep opportunity. A candidate gene approach was employed to analyze single-nucleotide polymorphisms from five circadian-related genes in a two-phase analysis of 84 healthy young adults (28 F; 23.21 ± 2.97 years) of European ancestry. A common variant in Period2 (PER2) was associated with 20 min less slow-wave sleep (SWS) in carriers of the minor allele than in noncarriers, representing a 22% reduction in SWS duration. Moreover, spectral analysis in a subset of participants (n = 37) showed the same PER2 polymorphism was associated with reduced EEG power density in the low delta range (0.25–1.0 Hz) during non-REM sleep and lower slow-wave activity (0.75–4.5 Hz) in the early part of the sleep episode. These results indicate the involvement of PER2 in the homeostatic process of sleep. Additionally, a rare variant in Melatonin Receptor 1B was associated with longer REM sleep latency, with minor allele carriers exhibiting an average of 65 min (87%) longer latency from sleep onset to REM sleep, compared to noncarriers. These findings suggest that circadian-related genes can modulate sleep architecture and the sleep EEG, including specific parameters previously implicated in the homeostatic regulation of sleep.     

Enhancement of REM sleep during extraocular light exposure in humans

This study examined the effects on sleep of light administered to an extraocular site. A 3-h photic stimulus was applied to the popliteal region during sleep in 14 human subjects. Each subject also underwent a control stimulus condition during a separate laboratory session. The proportion of rapid eye movement (REM) sleep during the 3-h light administration session increased by an average of 31% relative to the control condition. The frequency but not the duration of REM episodes was altered during light exposure, thereby shortening the REM/non-REM (NREM) cycle length. No other sleep stages were significantly affected during light administration nor was sleep architecture altered after the light-exposure interval. These results confirm that extraocular light is transduced into a signal that is received and processed by the human central nervous system. In addition, they expand to a novel sensory modality previous findings that REM sleep can be enhanced by sensory stimulation.     

Masking of the circadian rhythms of heart rate and core temperature by the rest-activity cycle in man

Heart rate and core temperature are elevated by physical activity and reduced during rest and/or sleep. These masking effects may confound interpretation of rhythm waveforms, particularly in situations where the rest-activity rhythm has a different period from that of the core temperature rhythm. Such desynchronization often occurs temporarily as an individual adjusts to a new work shift or to a new time zone following rapid transmeridian travel, making it difficult to assess the impact of such schedule changes on the circadian system. The present experiments were designed to estimate the magnitude of these masking effects, by monitoring the heart rate, rectal temperature, and nondominant wrist activity (2-min samples) of 12 male subjects during 6 days of normal routine outside the lab and during 6 days of strict bedrest. Subjects also kept sleep, dietary, and exercise logs throughout the study. Average (20-min) waveforms were computed for each subject and each rhythm, at home and in bedrest. In addition, data were partitioned according to self-reported sleep and wake times and were analyzed separately for each state. Average waveform comparisons indicated that about 45% of the range of the circadian heart rate rhythm during normal routine was attributable to the masking effects of activity during wake, which also produced a 16% elevation in mean heart rate during wake and an 11% increase in mean heart rate overall. (Analysis of variance indicated that mean heart rate during sleep at home was not significantly different from the mean during sleep in bedrest.) On average, about 14% of the range of the circadian temperature rhythm during normal routine was attributable to the effects of activity masking. However, the change in range of the temperature rhythm, from home to bedrest, was very variable between subjects (-41% to +13%). This variability was not accounted for by age or by reported frequency of exercise at home. Normal activity during wake increased the mean temperature during wake by an average of 0.16 degrees C and the overall mean by about 0.12 degrees C. (Analysis of variance indicated that mean temperature during sleep at home was not significantly different from the mean during sleep in bedrest.) A 10-hr "night" (lights-off from 2200 to 0800 hr) was provided during bedrest, within which subjects could select their own sleep times. Times of sleep onset and wake onset were not significantly different between home and bedrest.(ABSTRACT TRUNCATED AT 400 WORDS)     

Melatonin microinjection into the medial preoptic area increases sleep in the rat

A wide variety of hypnotic compounds including triazolam, pentobarbital, ethanol and adenosine have been reported to enhance sleep when microinjected into the medial preoptic area (MPA) of the anterior hypothalamus of the rat. It is uncertain whether the pineal hormone melatonin, which may alter sleep/wake physiology in mammals, acts at this site. A previous report has indicated that a more widespread injection of melatonin into the hypothalamus of the cat induces sleep. In the present study we have examined the possibility that the MPA may mediate this effect. Nine adult rats were microinjected with melatonin 1 and 50 ug and vehicle into the MPA during the daytime in a repeated measures design study. It was found that melatonin increased total sleep time in a dose-dependent manner, primarily by increasing NREM sleep, and that wake time after sleep onset was significantly reduced. These data add melatonin to the growing list of compounds that increase total sleep after administration into the MPA, and suggest that the MPA may be a common site of action for such agents from a variety of pharmacologic classes. Based on previous studies, the possibility is raised that this sleep enhancement results from an alteration in function of the GABA(A)-benzodiazepine receptor complex.     

Effects of intermittent lighting on sleep and activity in the domestic hen

This experiment deals with the effects of two different light-dark regimes on general activity, behavioural patterns and sleep in domestic hens (Gallus domesticus). The light-dark schemes were composed of a traditional 14 h light-10h dark period and the Biomittent Lighting Program (BMLP), which consists of only 15 min light during every hour of the traditional 14 h photoperiod. Although it was found that hens are more active during the day than during the night, they were much less active under the BMLP-regime compared to the traditional regime. More specifically, there is considerable lowering of their activities during the dark portions of the day; behavioural observations revealed that they spend these periods not with resting behaviour, but with passive wakefulness. They more or less concentrate their daily activities during the 15-min light periods. Under the night period of the BMLP-regime, hens appeared to be more restless. Sleep recordings showed that sleep tended to decrease in favour of more drowsiness.

It was concluded that circadian rhythmicity of the hens is maintained under both lighting schemes, although the BMLP-regime imposes more passive wakefulness during the day and slightly more activity during the night.     

Interdependence of learning and paradoxical sleep in the cat

The effect of learning sessions on the structure of the sleep-wakefulness cycle, as well as the effect of paradoxical sleep (PS) deprivation (PSD) following learning sessions, on the acquisition and extinction of instrumental alimentary reflexes to two feeders with sound discrimination, were studied on cats. The analysis of the data obtained led to following conclusions: The above learning sessions have no marked effect on the structure of the sleep-wakefulness cycle in the post-learning period, i.e. the percentage ratio of its phases is not altered by the increase of one of them. When PSD by non-emotional awakening is used, the number of PS onsets is not affected by learning sessions. This indicates that learning does not produce any considerable effect on the formation of PS need. PSD by non-emotional awakening following learning sessions does not retard the acquisition and extinction of the instrumental alimentary reflexes. The above data are interpreted as indicating that PS has no specific significance in memory trace consolidation during formation of long-term memory.     

Circadian fluctuations in the muscular efficiency of athletes: with sleep versus sleep deprivation

The influence of time of day on muscular performance was studied. From part of the results of two different studies (EAS et EPS), the effects of sleep deprivation were appreciated. Seven times over the 24-h period, developed torque and myoelectric activity were estimated during maximal isometric voluntary contractions using an isokinetic dynamometer: elbow flexion for EAS in standardised sleep, and knee extension for EPS in complete sleep deprivation. The results showed nycthemeral changes in torque in both conditions (p < 0.005), with maximal values recorded at the beginning of night. Although during sleep deprivation (EPS) the rhythm followed neurophysiological factors, during EAS, this rhythm was accounted for by the variations in the contractile state of muscle.     

Involvement of interaction of ZP1 and ZPC in the formation of quail perivitelline membrane

The extracellular matrix surrounding the oocyte before ovulation is called the perivitelline membrane (PL) in avian species. We have previously reported that one of its components, ZPC, is produced in ovarian granulosa cells by the stimulation of follicle-stimulating hormone and testosterone. Another component, ZP1, is synthesized in the liver and might be transported to the surface of the oocyte of the follicles. These glycoproteins are assembled to form a three-dimensional network of coarse fibers between the granulosa cells and the oocyte. In the present study, we have evaluated the involvement of the interaction of ZPC and ZP1 in the formation of the PL of Japanese quail. By measuring the incorporation of tritium-labeled proteins into the PL, we have found that tritium-labeled ZPC is specifically incorporated into the PL. Whole-mount autoradiographic analysis of the PL has also revealed the incorporation of the secreted ZPC into the isolated PL. To study which component in the PL is responsible for the specific incorporation of ZPC, PL lysates were incubated with the conditioned medium of the granulosa cells and were immunoprecipitated with anti-ZPC antiserum. Western blot analysis of the immunoprecipitated materials indicated that the 175-kDa and 97-kDa ZP1 forms were co-immunoprecipitated with anti-ZPC antiserum. These results demonstrate that ZPC secreted from the granulosa cells specifically binds with ZP1, and that the phenomenon might be involved in insoluble PL fiber formation in quail ovary.Funding for this work was provided by the Ministry of Education, Science, Sports and Culture of Japan (Grant-in-Aids for Scientific Research: 14760177 and 16780192 to T.S. and 15380191 to M.M.)