Circadian distribution of motor activity and immobility in narcolepsy: Assessment with continuous motor activity monitoring

The circadian distribution of motor activity and immobility of 14 unmedicated narcoleptics and matched controls was evaluated by monitoring continuous wrist motor activity 5 successive days and nights at home. Sleep was also assessed by sleep logs. The amplitude of the circadian rhythm of motor activity and immobility was significantly lower in narcoleptics than in controls. The variables that best distinguish narcoleptics from controls were the diurnal and nocturnal mean duration of uninterrupted immobility, which can be explained by excessive daytime sleepiness and frequent nocturnal awakenings, respectively. Thus, measures of diurnal and nocturnal motor activity and immobility appear useful for the objective assessment of some of the sleep-wakefulness manifestations of narcolepsy.     

45-Hour continuous quintuple-site actimetry: Relations between trunk and limb movements and effects of circadian sleep-wake rhythmicity

Diurnal and nocturnal trunk and limb motor activity of 20 healthy individuals was evaluated by actimetry for 45 consecutive hours. Sleep was assessed by sleep logs. Overall, motor activity significantly (p < .05) decreased in the order wrist, ankle, and trunk. There was significantly more motor activity in the dominant wrist during the diurnal period. Motor activity was significantly affected by the 24-hr sleep-wake cycle, with lower levels and prolonged immobility during the night. Time series analyses revealed different but significant correlations between motor activity at all sites. These data imply that (a) motor activity should be recorded at the dominant wrist when the highest level of motor activity is of importance, (b) recordings at the nondominant wrist are better indicators of trunk movement than are dominant wrist recordings, and (c) sites other than the conventional nondominant wrist recording site should be evaluated to improve the validity of motor activity-based sleep-wake scoring.     

Gross motor adaptation benefits from sleep after training

Sleep has been shown to facilitate the consolidation of newly acquired motor memories. However, the role of sleep in gross motor learning, especially in motor adaptation, is less clear. Thus, we investigated the effects of nocturnal sleep on the performance of a gross motor adaptation task, i.e. riding an inverse steering bicycle. Twenty‐six male participants (M = 24.19, SD = 3.70 years) were randomly assigned to a PM‐AM‐PM (n = 13) or an AM‐PM‐AM (n = 13) group, i.e. they trained in the evening/morning and were re‐tested the next morning/evening and the following evening/morning (PM‐AM‐PM/AM‐PM‐AM group) so that every participant spent one sleep as well as one wake interval between the three test sessions. Inverse cycling performance was assessed by speed (riding time) and accuracy (standard deviation of steering angle) measures. Behavioural results showed that in the PM‐AM‐PM group a night of sleep right after training stabilized performance (accuracy and speed) and was further improved over the subsequent wake interval. In the AM‐PM‐AM group, a significant performance deterioration after the initial wake interval was followed by the restoration of subjects' performance levels from right after training when a full night of sleep was granted. Regarding sleep, right hemispheric fast N2 sleep spindle activity was related to better stabilization of inverse cycling skills, thus possibly reflecting the ongoing process of updating the participants' mental model from “how to ride a bicycle” to “how to ride an inverse steering bicycle”. Our results demonstrate that sleep facilitates the consolidation of gross motor adaptation, thus adding further insights to the role of sleep for tasks with real‐life relevance.     

Hyperactive night and day? Actigraphy studies in adult ADHD: a baseline comparison and the effect of methylphenidate

STUDY OBJECTIVES: To investigate parameters of sleep, activity, and circadian rhythm, as well as the effects of methylphenidate on these variables, in adults with ADHD. DESIGN: 1) Baseline group comparison; 2) Double blind, placebo-controlled, cross-over medication trial. SETTING: Data collection took place during daily lives of participants. PARTICIPANTS: 39 normal controls and 33 adults with ADHD for baseline comparisons; 31 adults with ADHD in medication trial. INTERVENTIONS: Treatment with placebo and methylphenidate during medication trial. MEASUREMENTS AND RESULTS: Actigraphy and sleep log data were collected for 7 consecutive nights and days to obtain baseline values for ADHD and normal controls. Repeated measurements during placebo and methylphenidate treatment were conducted for the ADHD group. Actigraphic sleep estimates showed that ADHD subjects took longer to fall asleep, had lower sleep efficiency, and had shorter within-night periods of uninterrupted sleep. These findings were consistent with subjective complaints. Actigraphic measures of ADHD subjects showed continuously elevated daytime activity levels, resulting in a 24-hour pattern that was more stable and less variable than in controls. Methylphenidate led to a later bedtime, later sleep onset, and reduction in sleep duration. However, number and total duration of nocturnal awakenings decreased, while mean duration of within-night periods of uninterrupted sleep increased, indicating more consolidated sleep. CONCLUSIONS: Our data suggest that sleep problems are inherent in adults with ADHD and that methylphenidate reduced total sleep time but improved sleep quality by consolidating sleep.     

Insufficient non-REM sleep intensity in narcolepsy-cataplexy

STUDY OBJECTIVES: To compare electroencephalogram (EEG) dynamics during nocturnal sleep in patients with narcolepsy-cataplexy and healthy controls. Fragmented nocturnal sleep is a prominent feature and contributes to excessive daytime sleepiness in narcolepsy-cataplexy. Only 3 studies have addressed changes in homeostatic sleep regulation as a possible mechanism underlying nocturnal sleep fragmentation in narcolepsy-cataplexy. DESIGN, SETTING AND PARTICIPANTS: Baseline sleep of 11 drug-naive patients with narcolepsy-cataplexy (19-37 years) and 11 matched controls (18-41 years) was polysomnographically recorded. The EEG was subjected to spectral analysis. INTERVENTIONS: None, baseline condition. MEASUREMENTS AND RESULTS: All patients with narcolepsy-cataplexy but no control subjects showed a sleep-onset rapid eye movement (REM) episode. Non-REM (NREM)-REM sleep cycles were longer in patients with narcolepsy-cataplexy than in controls (P = 0.04). Mean slow-wave activity declined in both groups across the first 3 NREM sleep episodes (P<0.001). The rate of decline, however, appeared to be steeper in patients with narcolepsy-cataplexy (time constant: narcolepsy-cataplexy 51.1 +/- 23.8 minutes [mean +/- SEM], 95% confidence interval [CI]: 33.4-108.8 minutes) than in controls (169.4 +/- 81.5 minutes, 95% CI: 110.9-357.6 minutes) as concluded from nonoverlapping 95% confidence interval of the time constants. The steeper decline of SWA in narcolepsy-cataplexy compared to controls was related to an impaired build-up of slow-wave activity in the second cycle. Sleep in the second cycle was interrupted in patients with narcolepsy-cataplexy, when compared with controls, by an increased number (P = 0.01) and longer duration (P = 0.01) of short wake episodes. CONCLUSIONS: Insufficient NREM sleep intensity is associated with nonconsolidated nocturnal sleep in narcolepsy-cataplexy. The inability to consolidate sleep manifests itself when NREM sleep intensity has decayed below a certain level and is reflected in an altered time course of slow-wave activity across NREM sleep episodes.     

Nocturnal cortisol release in relation to sleep structure.

The relationship between the temporal organization of cortisol secretion and sleep structure is controversial. To determine whether the cortisol profile is modified by 4 hours of sleep deprivation, which shifts slow-wave sleep (SWS) episodes, 12 normal men were studied during a reference night, a sleep deprivation night and a recovery night. Plasma cortisol was measured in 10-minute blood samples. Analysis of the nocturnal cortisol profiles and the concomitant patterns of sleep stage distribution indicates that the cortisol profile is not influenced by sleep deprivation. Neither the starting time of the cortisol increase nor the mean number and amplitude of pulses was significantly different between the three nights. SWS episodes were significantly associated with declining plasma cortisol levels (p less than 0.01). This was especially revealed after sleep deprivation, as SWS episodes were particularly present during the second half of the night, a period of enhanced cortisol secretion. In 73% of cases, rapid eye movement sleep phases started when cortisol was reflecting diminished adrenocortical activity. Cortisol increases were not concomitant with a specific sleep stage but generally accompanied prolonged waking periods. These findings tend to imply that cortisol-releasing mechanisms may be involved in the regulation of sleep.     

Improvement of a patient's circadian rhythm sleep disorders by aripiprazole was associated with stabilization of his bipolar illness

Splitting of the behavioural activity phase has been found in nocturnal rodents with suprachiasmatic nucleus (SCN) coupling disorder. A similar phenomenon was observed in the sleep phase in the diurnal human discussed here, suggesting that there are so‐called evening and morning oscillators in the SCN of humans. The present case suffered from bipolar disorder refractory to various treatments, and various circadian rhythm sleep disorders, such as delayed sleep phase, polyphasic sleep, separation of the sleep bout resembling splitting and circabidian rhythm (48 h), were found during prolonged depressive episodes with hypersomnia. Separation of sleep into evening and morning components and delayed sleep‐offset (24.69‐h cycle) developed when lowering and stopping the dose of aripiprazole (APZ). However, resumption of APZ improved these symptoms in 2 weeks, accompanied by improvement in the patient's depressive state. Administration of APZ may improve various circadian rhythm sleep disorders, as well as improve and prevent manic–depressive episodes, via augmentation of coupling in the SCN network.     

Alexithymia and polysomnographic measures of sleep in healthy adults

OBJECTIVE: This study examined associations between alexithymia and objective characteristics of sleep (latencies, stages, and amount and patterning of REM sleep) that may contribute to subjective reports of poor sleep quality and impaired dream recall among alexithymic people. METHODS: Fifty healthy, normally sleeping adults from the community completed the 20-item Toronto Alexithymia Scale and slept uninterrupted for one night in the laboratory while polysomnography was conducted. Various measures of sleep latency, sleep stages, and REM sleep-related variables were obtained, and analyses correlated these sleep measures with alexithymia, controlling for age, sex, and level of depressed affect. RESULTS: Higher alexithymia scores were significantly related to increased stage 1 (light) sleep and decreased stage 3/4 (deep) sleep. Alexithymia was unrelated to overall sleep efficiency or percentage of stage 2 sleep. Alexithymia was related to more frequent REM episodes and more stage 1 sleep during and immediately after REM episodes but was unrelated to the absolute amount of REM sleep. Alexithymia was also related to an earlier onset of the first REM episode. CONCLUSIONS: Alexithymia is associated with more light sleep and less deep sleep, which may contribute to subjective reports of poor sleep and increased sleepiness, fatigue, and somatic symptoms. Although alexithymia is not associated with an overall reduction of REM sleep, the increased frequency of episodes of REM that are interrupted and followed by light sleep rather than complete awakenings may contribute to limited dream recall.     

Relationship between sleep and acid gastro-oesophageal reflux in neonates

The aim of the present study was to investigate the impact of gastro‐oesophageal acid reflux on sleep in neonates and, reciprocally, the influence of wakefulness (W) and sleep stages on the characteristics of the reflux (including the retrograde bolus migration of oesophageal acid contents). The pH and multichannel intraluminal impedance were measured during nocturnal polysomnography in 25 infants hospitalised for suspicion of gastro‐oesophageal reflux. Two groups were constituted according to whether or not the infants displayed gastro‐oesophageal reflux (i.e. a reflux group and a control group). There were no differences between the reflux and control groups in terms of sleep duration, sleep structure and sleep state change frequency. Vigilance states significantly influenced the gastro‐oesophageal reflux pattern: the occurrence of gastro‐oesophageal reflux episodes was greater during W (59 ± 32%) and active sleep (AS; 35 ± 30%) than during quiet sleep (QS; 6 ± 11%), whereas the mean duration of gastro‐oesophageal reflux episodes was higher in QS than in W and AS. The percentage of retrograde bolus migrations of distal oesophageal acid content was significantly higher in AS (62 ± 26%) than in W (42 ± 26%) and QS (4.5 ± 9%). In neonates, gastro‐oesophageal reflux occurred more frequently during W, whereas the physiological changes associated with sleep state increase the physiopathological impact of the gastro‐oesophageal reflux. The duration of oesophagus–acid contact was greater during sleep; AS facilitated the retrograde migration of oesophageal acid content, and QS was characterised by the risk of prolonged acid mucosal contact.     

Actigraphy suggests age-related differences in napping and nocturnal sleep

The aim of this study was to contrast the time distribution of out-of-bed napping in young and older adults through recordings of wrist activity, and to evaluate the correlates of napping with nocturnal sleep. Seventy-three young adults between 18 and 32 years and 60 older adults between 60 and 75 years of age participated in the study. Subjects were selected for good general health and had few sleep complaints. They wore wrist-activity monitors and kept daily sleep logs for 1 week. Automatic sleep scoring was edited by the authors, supplemented by sleep logs and illumination data as well as activity data. Napping episodes were modestly increased in older adults, but there was no difference in the daily duration of napping. Older adults napped more in the evening (especially within 2 h before bedtime), whereas young adults napped more in the afternoon. The older adults with evening naps (n = 31) showed earlier nocturnal wake-up times and decreased nocturnal sleep duration compared with the older adults without evening naps (n = 29). There was no difference in nocturnal sleep between young adults with afternoon naps (n = 32) and without afternoon naps (n = 41). In determining the effects of napping on nocturnal sleep, timing of napping and age are important. Maintaining alertness during the evening (e.g. by bright light exposure or moderate exercise) would be a possible approach to delay wake-up times in older adults.     

A 20-h recovery sleep after prolonged sleep restriction: some effects of competing in a world record-setting cinemarathon

SUMMARY  The recovery sleep of a 21-year-old normal woman was assessed after she had endured 11 1/2 days of sleep restriction in a world record-setting film-viewing marathon. An exceptional sleep debt was observed as indicated by an instanteous sleep onset, a high sleep efficiency, and a total sleep duration of over 20 hours. Other striking features of this recovery sleep were very short latencies to stages 3 and 4 sleep, return of Stage 4 sleep after 14.5 h, REM and SWS sleep rebound, and a linear increase in REM sleep efficiency across 14 consecutive REM-NREM episodes. Seven of nine home dreams reported after this recording contained competition themes, but none relating to the marathon films. Comparisons of the present results with those from subjects in previous record-setting events suggest possible explanations for the extremely long recovery sleep. Results also suggest that analyses of multiple consecutive sleep cycles may provide novel ways of assessing hypotheses about regulation of the REM-NREM cycle.     

Is the nonREM-REM sleep cycle reset by forced awakenings from REM sleep?

In selective REM sleep deprivation (SRSD), the occurrence of stage REM is repeatedly interrupted by short awakenings. Typically, the interventions aggregate in clusters resembling the REM episodes in undisturbed sleep. This salient phenomenon can easily be explained if the nonREM-REM sleep process is continued during the periods of forced wakefulness. However, earlier studies have alternatively suggested that awakenings from sleep might rather discontinue and reset the ultradian process. Theoretically, the two explanations predict a different distribution of REM episode duration.We evaluated 117 SRSD treatment nights recorded from 14 depressive inpatients receiving low dosages of Trimipramine. The alarms were triggered by an automatic mechanism for the detection of REM sleep and had to be canceled by the subjects themselves. The REM episodes were determined as in undisturbed sleep-they had to include the remaining REM activity and were separated by 30 min without REM epochs. The frequency histogram of REM episodes declined exponentially with episode duration for each of the first four sleep cycles. The duration of nonREM intervals revealed bimodal distributions. These results were found consistent with the model assuming a reset of the ultradian cycle upon awakening. Whether REM or nonREM activity is resumed on return to sleep can be modeled by a random decision whereby the probability for REM sleep might depend on the momentary REM pressure.     

Interictal, potentially misleading, epileptiform EEG abnormalities in REM sleep behavior disorder

STUDY OBJECTIVES: To examine the implications of interictal epileptiform abnormalities (IEA) in idiopathic REM-sleep behavior disorder (RBD), particularly the risk of misdiagnosing RBD episodes as epileptic nocturnal seizures. DESIGN: Observational analysis and review. SETTING: Tertiary sleep center. PATIENTS: Thirty patients (28 men; mean age 66.3 +/- 7.5 years) referred to our sleep unit for a definite diagnosis of nocturnal sleep-related motor and behavioral paroxysmal episodes. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: All the patients were found to be affected by idiopathic RBD according to standard clinical and videopolysomnographic criteria. IEA(sporadic, fronto-temporal sharp-waves) were detected in 8 subjects (26.6%) during routine electroencephalogram and/or nocturnal in-lab videopolysomnography with extended EEG montages. In 2 of these 8 patients, IEA occurred during REM sleep. CONCLUSIONS: When only the clinical history is considered, RBD episodes may be confused with nocturnal epileptic focal seizures. The presence of IEA either on routine awake electroencephalograms, or during sleep electroencephalograms, may add support for a diagnosis of epileptic nocturnal seizures. Our data show that IEA may occur in wake and sleep (non rapid eye movement and rapid eye movement sleep) tracings of subjects with episodes of idiopathic RBD. However full-night extended electroencephalogram montages and polysomnography recording of an episode proved useful in establishing a definite diagnosis of RBD in these potentially misleading cases. Comparison of the patients' demographic data and RBD features revealed no differences between RBD with IEA and without IEA. On this basis-and given that these abnormalities have also been described in elderly people with wakefulness-related nonepileptic disorders-IEA in RBD could simply be interpreted as a nonspecific phenomenon, probably related to brain aging.     

Sleep patterns in the Mongolian gerbil, Meriones unguiculatus

Sleep patterns were studied in Mongolian gerbils and normative values were derived from 48 hour recordings, during a 24-hr light-dark cycle (LD 12:12). Behavioral and electrographic observations confirmed the existence of well defined sleep states: slow-wave sleep (SWS) and paradoxical sleep (PS). During the light period, sleep occupied slightly more than half of the 12 hour period, 57.13 +/- 0.002% out of which 49.64 +/- 0.007% was occupied by SWS and 8.07 +/- 0.007% by PS. There were 23 +/- 0.01 episodes of PS with a mean duration of 2.32 +/- 0.01 min. During the dark period, sleep occupied slightly less than half of the recording time (51.75 +/- 0.01%). They spent 41.62 +/- 0.006% in SWS and 10.12 +/- 0.02% in PS. The number of PS episodes was 32 +/- 0 with a mean duration of 2.28 +/- 0.01 min. Sleep cycle duration was 7.80 +/- 3.76 min. The ratio day/night sleep was 1.17 +/- 0.002 min. We found that the gerbil in captivity, unlike most rodents that are nocturnal, is a crepuscular animal, being more active at the transitions between light and dark.     

Relative and combined effects of heat and noise exposure on sleep in humans.

In a counter-balanced design, the effects of daytime and/or nighttime exposure to heat and/or traffic noise on night sleep were studied in eight healthy young men. During the day, the subjects were exposed to baseline condition (ambient temperature = 20 degrees C; no noise) or to both heat (35 degrees C) and noise. The duration of the daytime exposure was 8 h ending 5 h before sleep onset. The following nights, the subjects slept either in undisturbed (20 degrees C; no noise) or in noise, heat, or noise plus heat-disturbed environments. During the day, the various types of traffic noise were distributed at a rate of 48/h with peak intensities ranging between 79 and 86 dB(A). The background noise level was at 45 dB(A). At night, the peak intensities were reduced by 15 dB(A), the rate was diminished to 9/h, and the background noise was at 30 dB(A). Electrophysiological measures of sleep and esophageal and mean skin temperatures were continuously recorded. The results showed that both objective and subjective measures of sleep were more disturbed by heat than by noise. The thermal load had a larger impact on sleep quality than on sleep architecture. In the nocturnal hot condition, total sleep time decreased while duration of wakefulness, number of sleep stage changes, stage 1 episodes, number of awakenings, and transitions toward waking increased. An increase in the frequency of transient activation phases was also found in slow-wave sleep and in stage 2. In the nocturnal noise condition, only total number of sleep stage changes, changes to waking, and number of stage 1 episodes increased.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characteristics of spontaneous sleep with varying NREMS Episodes in healthy men: implication for delta activity homeostasis

STUDY OBJECTIVES: We investigated the effects of the variation in the number of NREMS episodes on human sleep, in particular on delta activity distribution. PARTICIPANTS: Forty-one medication-free healthy men without personal or family history of psychiatric disorders. INTERVENTIONS: Subjects slept four consecutive nights, the last three were analyzed. Sleep was undisturbed and uninterrupted following self-selected schedule. RESULTS: With the exception of one night out of 123, subjects slept at least four NREMS episodes with 80% presenting five or six episodes per night. Yet, only 24% slept the same number of NREMS episodes across three nights. Shorter first NREMS episode was associated with greater number of NREMS episodes, and the total number of NREMS episodes was significantly predicted by the duration of the first one. Whether subjects slept four, five or six NREMS episodes, the proportion of TST spent in REMS, total delta power, total spectral power and the rate of delta power in the first NREMS episode did not differ between subjects. In each night, the distribution of delta activity across the first four NREMS episodes was not modified by the total number of NREMS episodes. CONCLUSION: When spontaneous sleep is allowed, healthy men mostly sleep beyond the fourth NREMS episode. Based on delta activity distribution across the first four episodes, we have demonstrated that the number of NREMS episodes does not modify delta sleep homeostasis. Only duration of first NREMS episode predicts the number of NREMS episodes slept. These results suggest that sleep homeostasis and NREMS-REMS alternation may be two independent processes.     

Effect of continuous heat exposure on sleep stages in humans

Six young men were exposed to a thermoneutral environment of air temperature (Ta) 20 degrees C for 5 days and nights followed by an acclimation period of 5 days and nights at Ta 35 degrees C and 2 recovery days and nights at Ta 20 degrees C. Electrophysiological measures of sleep, esophageal temperature, and mean skin temperature were continuously monitored. The total nocturnal body weight loss was measured by a sensitive platform scale. Compared with the 5 nights of the baseline period at 20 degrees C, sleep patterns showed disturbances at 35 degrees C. Total sleep time was significantly reduced, while the amount of wakefulness increased. The subjects exhibited fragmented sleep patterns. The mean duration of REM episodes was shorter at 35 degrees C than at 20 degrees C of Ta, while the REM cycle length shortened. In the acclimation period, there was no change in sleep pattern from night to night, despite adaptative adjustments of the thermoregulatory response. The protective mechanisms of deep body temperature occurring with heat adaptation did not interact with sleep processes. Upon return to baseline condition, a recovery effect was observed on a number of sleep parameters which were not significantly affected by the preceding exposure to prolonged heat. This would suggest that during exposure to dry heat, the demand for sleep could overcome that of other regulatory functions that are temperature-dependent. Therefore, a complete analysis of the effect of heat on sleep parameters can be assessed only if heat exposure is compared with both baseline and recovery periods.     

Sleep deprivation in honey bees

Rest at night in forager honey bees (Apis mellifera) meets essential criteria of sleep. This paper reports the effect of a 12-h total sleep deprivation (SD) by forced activity on the behaviour of these animals. The behaviour of sleep-deprived animals is compared with that of control animals under LD [periodic alternation between light (L) and darkness (D)] 12 : 12 hours. SD for 12 h during the first D period resulted in a significant difference with respect to the parameter 'hourly amount of antennal immobility' between sleep-deprived and control animals during the remaining L and D periods. This difference did not occur in the L period following the deprivation night, but rather it became obvious at the beginning of the following D period. The increase of the amount of antennal immobility in sleep-deprived bees was accompanied by an increase of the duration of episodes of antennal immobility. Moreover, the latency from 'lights off' to the first episode of antennal immobility lasting 20 s or longer ('deep sleep latency') tended to be shorter in sleep-deprived than in control animals. Disturbing the bees during the day (L period) did not result in such differences between disturbed and control animals. Highest reaction thresholds in sleeping honey bees occur during long episodes of antennal immobility. We therefore conclude that honey bees compensate a sleep deficit by intensification (deepening) of the sleep process and thus that sleep in honey bees, like that in other arthropods and mammals, is controlled by regulatory mechanisms.     

Sleep homeostasis in Drosophila melanogaster

STUDY OBJECTIVES: The fruit fly Drosophila melanogaster is emerging as a promising model system for the genetic dissection of sleep. As in mammals, sleep in the fruit fly is a reversible state of reduced responsiveness to the external world and has been defined using an array of behavioral, pharmacologic, molecular, and electrophysiologic criteria. A central feature of mammalian sleep is its homeostatic regulation by the amount of previous wakefulness. Dissecting the mechanisms of homeostatic regulation is likely to provide key insights into the functions of sleep. Thus, it is important to establish to what extent sleep homeostasis is similar between mammals and flies. This study was designed to determine whether in flies, as in mammals, (1) sleep rebound is dependent on prior time awake; (2) sleep deprivation affects the intensity, in addition to the duration, of sleep rebound; (3) sleep loss impairs vigilance and performance; (4) the sleep homeostatic response is conserved among different wild-type lines, and between female and male flies of the same line. DESIGN: Motor activity of individual flies was recorded at 1-minute intervals using the infrared Drosophila Activity Monitoring System during 2 baseline days; during 6, 12, and 24 hours of sleep deprivation; and during 2 days of recovery. Sleep was defined as any period of uninterrupted behavioral immobility lasting > 5 minutes. Sleep continuity was measured by calculating the number of brief awakenings, the number and duration of sleep episodes, and a sleep continuity score. Vigilance before and after sleep deprivation was assessed by measuring the escape response triggered by 2 different aversive stimuli. SETTING: Fly sleep research laboratory at UW-Madison. PARTICIPANTS AND INTERVENTIONS: Adult flies of the Canton-S (CS) strain and 116 other wild-type lines (> or = 16 female and > or = 16 male flies per line). MEASUREMENTS AND RESULTS: In wild-type CS flies, as in mammals, the amount of sleep recovered after sleep deprivation was dependent on prior time awake. Relative to baseline sleep, recovery sleep in CS flies was less fragmented, with longer sleep episodes, and was associated with a higher arousal threshold. Sleep deprivation in CS flies also reduced performance. Sleep duration and continuity increased after 24 hour of sleep deprivation in all the other wild-type lines tested. CONCLUSION: The sleep homeostatic response in fruit flies is a stable phenotype and shares most of, if not all, the major features of mammalian sleep homeostasis, thus supporting the use of Drosophila as a model system for the genetic dissection of sleep mechanisms and functions.     

The duration of REM sleep epic, odes in normal sleep

SUMMARY  The distributions of the durations of the first 3 REM sleep episodes have been analysed using a total of 134 overnight sleep recordings from 10 subjects. From investigation of the length of uninterrupted episodes of stage REM, it is shown that arousals to stage 0/1 could play an important part in the process of REM exit, and that by the middle of the sleep period, these arousals probably occur according to a Poisson process. During the first and second REM episodes a more complex process appears to be at work, which could reflect increased pressure for slow wave sleep. These findings suggest that the duration of a REM episode is determined by a process that has a large stochastic element, which is not necessarily tied to REM entry.