A model for the timing of human sleep is presented. It is based on a sleep-regulating variable (S)--possibly, but not necessarily, associated with a neurochemical substance--which increases during wakefulness and decreases during sleep. Sleep onset is triggered when S approaches an upper threshold (H); awakening occurs when S reaches a lower threshold (L). The thresholds show a circadian rhythm controlled by a single circadian pacemaker. Time constants of the S process were derived from rates of change of electroencephalographic (EEG) power density during regular sleep and during recovery from sleep deprivation. The waveform of the circadian threshold fluctuations was derived from spontaneous wake-up times after partial sleep deprivation. The model allows computer simulations of the main phenomena of human sleep timing, such as 1) internal desynchronization in the absence of time cues, 2) sleep fragmentation during continuous bed rest, and 3) circadian phase dependence of sleep duration during isolation from time cues, recovery from sleep deprivation, and shift work. The model shows that the experimental data are consistent with the concept of a single circadian pacemaker in humans. It has implications for the understanding of sleep as a restorative process and its timing with respect to day and night.

Timing of human sleep: recovery process gated by a circadian pacemaker

Sleep deprivation: Effect on sleep stages and EEG power density in man

Several paradigms of perceptual learning suggest that practice can trigger long-term, experience-dependent changes in the adult visual system of humans. As shown here, performance of a basic visual discrimination task improved after a normal night's sleep. Selective disruption of rapid eye movement (REM) sleep resulted in no performance gain during a comparable sleep interval, although non-REM slow-wave sleep disruption did not affect improvement. On the other hand, deprivation of REM sleep had no detrimental effects on the performance of a similar, but previously learned, task. These results indicate that a process of human memory consolidation, active during sleep, is strongly dependent on REM sleep.

https://science.sciencemag.org/content/sci/265/5172/679.full.pdf

Dependence on REM sleep of overnight improvement of a perceptual skill

Study Objectives: This study provides estimates of reliability for aggregated values from 1 to 7 recording nights for five commonly used actigraphic measures of sleep patterns, reliability as a function of night type (weeknight or weekend night), and stability of measures over several months. Design and Setting: Data are from three studies that obtained 7 nights of actigraph data (using Mini Motionlogger actigraphs and associated validated algorithms [ASA]) on children and adolescents living at home on self-selected sleep-wake schedules. Participants: Participants were 169 children aged 12-60 months, and 55 adolescents aged 11-16 years. Measurements and Results: Up to 28% of weekly recordings may be unacceptable for analysis in young participants because of illness, technical problems, and participant noncompliance; studies aiming to collect 5 nights of actigraph data should record for at least 1 full week. Reliability estimates for values aggregated over any 5 nights were adequate (≥.70) for sleep start time, wake minutes, and sleep efficiency. Measures of sleep minutes and sleep period were less reliable and may require 7 or more nights for estimates of stable individual differences. Reliability for 1- or 2-night aggregates were poor for all measures. We found significant and high correlations between summer and fall session measures for all five variables when weekend nights were included. Conclusions: Five or more nights of usable recordings are required to obtain reliable actigraph measures of sleep for chil

/pdf/estimating-sleep-patterns-with-activity-monitoring-in-300yrxx6d9.pdf

Estimating sleep patterns with activity monitoring in children and adolescents: how many nights are necessary for reliable measures?

Two groups of young, healthy, nonathletic volunteers were subjected to selective sleep stage deprivation. Six subjects were deprived of stage 4 sleep and seven subjects of REM sleep. The stage 4 deprived group reported more musculoskeletal symptoms during the deprivation condition than did the REM deprived group. The stage 4 deprived group also showed a significant increase in muscle tenderness between the baseline and deprivation conditions and an altered pattern of overnight change in muscle tenderness in response to deprivation. The REM deprived group did not show either of these changes. These results are discussed in the light of the previously postulated relationship between NREM sleep disturbance and muscoloskeletal pain in patients with so-called "Fibrositis syndrome."

Induction of neurasthenic musculoskeletal pain syndrome by selective sleep stage deprivation.

Twelve young (17–21 yrs) male Navy recruits volunteered for a sleep loss study. After 4 baseline days, the Ss were completely deprived of sleep for 2 days and nights. Next followed an experimental phase of 2 days and nights after which all Ss received 2 nights of uninterrupted sleep.



During the experimental phase, the 4 Ss in the REM-deprived group were aroused whenever they showed signs of REM sleep. The 4 Ss of the stage 4-deprived group were aroused whenever they showed signs of entering stage 4 sleep, and the 4 Ss of the Control group had uninterrupted sleep.



All tests (speed and accuracy of addition, speed and accuracy of self-paced vigilance, errors of omission in experimenter paced vigilance, immediate recall of word lists, and mood) showed significant impairment after the first night of complete sleep loss. But during the experimental (sleep-stage-deprivation) and recovery phases, all three groups showed equal rates of recovery.



Depriving the S of stage REM or stage 4 during recovery sleep does not affect the recuperation rate. Frequent arousals (50–100 per night) also do not impair recovery. The amount of sleep is probably more important than the kind of sleep.

The Recuperative Effects of REM Sleep and Stage 4 Sleep on Human Performance After Complete Sleep Loss: Experiment 1

: The reliability of sleep measures was calculated over two nights (and within the nights) for twenty young adult males. Percent time in stages 1, 2, 3, and 4, percent movement time, number of movements, and number of stage changes were significantly correlated between subjects over nights. The percent REM time and REM cycle duration were not significantly correlated over nights. Within subjects, the length of the REM period had a significant negative correlation with the length of the preceding NREM period but not with the following NREM period. These data raise questions as to the use of the standard sleep measures as a reliable human traits in young male adults.

Reliability of sleep measures.

To determine whether prior deprivation of stage REM or stage 4 sleep would potentiate the effects of total sleep loss, 7 young adult males were denied REM sleep and 7 were denied stage 4 sleep for 3 nights before 1 night of total sleep loss. Measures of autonomic and EEG activity, mood, anxiety, Rorschach CET and on several performance tasks were obtained during baseline, following stage deprivation, total sleep loss, and during recovery.

There were no marked changes in any area following 3 nights of stage REM and stage 4 deprivation. The changes following total sleep loss were similar for both groups. Prior deprivation of stage REM or stage 4 did not potentiate sleep loss effects. Ss who had no stage deprivation prior to 1 night of sleep loss had more impairment following sleep loss than did the Ss of this study.

Interaction of REM deprivation and stage 4 deprivation with total sleep loss: experiment 2.

The combined effects of total sleep loss and the deprivation of stage 4 or stage REM were studied in I two separate experiments. Two full nights or sleep loss preceded stage 4 deprivation or stage REM deprivation in Experiment 1 (N=12); 1 full night of sleep loss followed 3 nights or stage 4 deprivation or stage REM deprivation in Experiment 2 (N=I4).



Total sleep loss before sleep stage deprivation significantly increased the number of attempts to enter stage 4, but had little influence on stage REM. A significant REM rebound was found in only one of the REM-deprived groups, but there was a significant stage 4 rebound in all groups on the first full recovery night, supporting the hypothesis from other studies that stage 4 has priority over REM in terms of recovery from sleep loss. The results suggested that stages 2, 3, and 4 partially overlap in their recuperative functions.

Sleep Stage Deprivation and Total Sleep Loss: Effects On Sleep Behavior

NORMAL nocturnal monophasic sleep is characterised by the cyclic alternation of rapid eye movement (REM) and nonrapid eye movement (NREM) sleep, with the REM phase of this cycle recurring approximately every 90–110 min. Kleitman1 hypothesised that an analogous 90–110 min basic rest–activity cycle (BRAC) exists during the awake state, implying a biological clock that continues to operate with the same periodicity throughout the 24-h period (that is, an activity-independent clock). We report here on the effect of altered sleep–wake schedules on the REM cycle and present evidence that the REM cycle is sleep-dependent—it operates only when the organism is sleeping and is not an expression of an activity-independent rhythm.

Julie Moses

Papers

The Recuperative Effects of REM Sleep and Stage 4 Sleep on Human Performance After Complete Sleep Loss: Experiment 1

Reliability of sleep measures.

Interaction of REM deprivation and stage 4 deprivation with total sleep loss: experiment 2.

Sleep Stage Deprivation and Total Sleep Loss: Effects On Sleep Behavior

Rapid eye movement cycle is a sleep-dependent rhythm