Showing papers on "Slow-wave sleep published in 1985"

Assessing performance upon abrupt awakening from naps during quasi-continuous operations

Abstract: Quasi-continuous work settings often involve sleep loss and requirements to perform at unpredictable times. Napping may alleviate some of the sleep-loss problems, but it increases the risk that the person will have difficulty functioning upon abrupt awakening. This paper describes an experimental approach, techniques, and analyses for investigating performance upon abrupt awakening from 2 h naps placed near either the circadian peak (P) or trough (T) in body temperature and preceded by 6, 18, 30, 42, or 54 h of sleep deprivation. Five groups of healthy young adults performed quasi-continuously for 54 h and were permitted a 2-h nap at one of five times. Reaction time (RT) to answer a phone terminating the nap, subjective estimates, and performance of a brief, challenging cognitive task were related to nap-sleep parameters of each group. Sleep deprivation increased the amount of deep sleep in the naps, and this was associated with greater postnap cognitive performance decrements; subjective estimates were unaffected, and RT performance was related simply to stage of sleep prior to awakening. Circadian placement of the naps also modulated the postnap cognitive decrement: T naps produced greater cognitive decrements than P naps, even when the latter involved more prior sleep loss. These findings have both practical and theoretical significance for evaluating the awakening process, and would not have been possible without the approach, techniques, and procedures described.

Further Evidence of Abnormal Non-Rapid-Eye-Movement Sleep in Schizophrenia

Abstract: • Very low levels of visually scored stage 4 sleep are found in 40% to 50% of acute and chronic schizophrenics. Stage 4 is a visual estimate of high-amplitude delta (0.5 to 3 Hz) electroencephalographic waves; these waves can now be measured directly and reliably by computer. In this pilot study, we carried out such measurement in the successive non-rapid-eye-movement periods (NREMPs). We also sampled and measured visually sleep spindles by NREMP; spindles constitute a second distinctive feature of the NREM electroencephalogram. In five unmedicated, recently rehospitalized schizophrenic patients we found reduced delta amplitude and abundance (and increased spindle density) in NREMP1 (also called "REM latency") as compared with ambulatory normal controls. NREMP1 was also abnormally short with an average length similar to that reported for major depression. These striking abnormalities of NREM sleep may underlie the abnormal rapid eye movement distributions sometimes found in schizophrenic and depressed patients. Further studies are required to evaluate the relation of these NREM abnormalities to psychopathology (and hence their utility as biological "markers") and to rule out confounding effects of hospitalization or undetected napping.

Role of adenosine in sleep in rats.

Abstract: The effects on sleep of N6-L-(phenylisopropyl) adenosine, cyclohexyladenosine and adenosine-5'-ethylcarboxamide were studied in rats. Also, the effects on sleep of deoxycoformycin, a potent inhibitor of adenosine deaminase, and adenosine were examined. In addition, we determined the effects of 48 h of REM sleep deprivation on adenosine (A1) receptors in specific brain structures. N6-L-(phenylisopropyl) adenosine and cyclohexyl-adenosine increased deep slow wave sleep and REM sleep whereas adenosine-5'-ethylcarboxamide increased only deep slow-wave sleep. At the dose of 0.9 mumol/kg all three adenosine analogs suppressed REM sleep and except for adenosine-5-ethylcarboxamide, were without an effect on deep slow-wave sleep. In accordance, administration of deoxycoformycin increased REM and deep slow-wave sleep. Intracerebroventricular administration of 1, 10 and 100 nmoles of adenosine to rats decreased waking, increased deep slow-wave sleep and increased total sleep. In addition, REM sleep deprivation significantly increased the number of A1 receptors (Bmax) in cerebral cortex and corpus striatum which correlates with the increased pressure for REM sleep and the onset of REM sleep rebound. When these data are taken together, they indicate a role for adenosine in the regulation of sleep and, in contrast to barbiturate and benzodiazepine hypnotics, increase in behaviorally deep and REM sleep.

Ventilatory and arousal patterns during sleep in normal young and elderly subjects.

Abstract: Since elderly subjects have lower chemosensitivity, we postulated that ventilation might be more state dependent in the elderly. To address this we investigated the changes in ventilation, measured by respiratory inductive plethysmography, with sleep in 12 healthy young (19-29 yr) and 13 elderly (greater than 65 yr) subjects. Ventilation was measured in representative periods in each sleep state. These data showed that there is no difference between the elderly and the young either in mean ventilation or in the variability of ventilation awake or in the different states of sleep. In both groups ventilation was variable in stage 1-2 sleep and least variable in stage 3-4 sleep. The variability in stage 1-2 sleep was due to periodic breathing (cycle time approximately 45 s) in both age groups. Although within a sleep state no differences were observed, over the night of study the elderly behaved differently from the young. Apneas occurred more frequently in the elderly, and 5 of 13 elderly met the criteria for sleep apnea syndrome compared with 1 of 12 young subjects. Apneas tended to occur predominantly in stage 1-2 sleep and seem to be an exaggeration of the periodicity that is typical of this state. Four of the elderly with apnea remained in this stage of sleep throughout the night of study. The apneic episodes usually terminated with an electroencephalogram arousal that occurred prior to or simultaneously with the onset of ventilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Napping behavior during "spontaneous internal desynchronization": sleep remains in synchrony with body temperature.

Abstract: Patterns of sleep and wakefulness exhibited in an environment without time cues are generally considered to be monophasic, with a distinct relationship between sleep episodes and the minimum of body core temperature. In some cases this relationship between major sleep episodes and temperature becomes replaced by an apparently varying phase relationship between the two variables called "spontaneous internal desynchronization". In the present study the sleep-wake and temperature data of six subjects living in an environment without time cues and exhibiting internal desynchronization were reanalyzed to include subjectively designated naps. Two groups of naps were identified based on their phase positions relative to temperature, with one group occurring around the temperature minimum and another group clustering approximately halfway between successive minima. The results support the suggestion that neither monophasic sleep placement nor sleep patterns typically associated with spontaneous internal desynchronization reflect biological sleep tendency. Rather, sleep tendency is reflected more accurately by the bimodal sleep patterns exhibited by subjects who are allowed to time their sleep and waking with no restrictions.

Are Microarousals Preceded by Electroencephalographic Slow Wave Synchronization Precursors of Confusional Awakenings

Abstract: The number of microarousals preceded by electroencephalographic (EEG) slow wave synchronization (MAS) and the number not preceded by EEG slow wave synchronization (K-complexes and/or delta groups) (MA) were analyzed during the first night of sleep in nine young patients with somnambulism and/or sleep terrors and in eight age- and sex-matched controls. While MAs peaked in REM ad intermediate sleep, MASs appeared as a phenomenon of NREM sleep, peaking in stage 2. The number of MASs was significantly greater in all stages of NREM sleep in the patient group, but number and distribution of MAs did not differ between the two groups. In the patient group, the MASs occurred in slow wave sleep (stages 3-4 of each sleep cycle); in controls, MASs occurred infrequently. MASs were frequently associated with automatic chewing movements. The higher frequency of microarousals in the patient group did not result in an increase in time awake during the night. The increase in number of microarousals supports Broughton's hypothesis of the presence of some "arousal disorder" in somnambulism and/or sleep terrors. MASs may be predictive markers of ensuing confusional awakenings.

Electroencephalographic sleep of younger depressives. Comparison with normals.

Abstract: • The electroencephalographic sleep of younger depressives (aged 20 to 44 years) was compared with that of an age-matched group of normals The patients demonstrated many of the typical sleep changes reported for older depressed populations: shortened rapid-eye-movement (REM) latency; REM sleep activity alterations, with a shift to the early portion of the night (first REM period); reduced delta sleep; and sleep efficiency reductions marked by sleep-onset difficulties The traditional scoring procedures were supplemented by automated REM and delta-sleep analyses that provided more precise delineation of these differences between patients and normals, particularly the distributions of REM activity and delta-wave patterning

On the origin of early REM episodes in the sleep of depressed patients: a comparison of three hypotheses.

Abstract: Shortened latency of rapid eye movement (REM) sleep is a feature frequently observed in depressed patients. Three hypotheses on the origin of early REM sleep episodes propose that short REM latency is due to (1) a phase-shift of one subset of the circadian rhythms relative to other circadian rhythms, (2) a loss of inhibition of REM sleep due to a slow wave sleep deficit, or (3) a reduction in amplitude of a putative circadian arousal cycle. From an analysis of experimental data, it is concluded that the hypothesis of a reduced circadian amplitude best explains the early occurrence of REM sleep.

Sleep in the Prader-Willi syndrome.

Abstract: To the Editor. —Dr Vela-Bueno and colleagues 1 suggest that their finding of sleep-onset rapid-eye movement periods (SOREMPs) in the nocturnal sleep in five of nine patients with Prader-Willi syndrome (PWS) was due to hypothalamic dysfunction. They failed to mention that a shortened REM sleep latency could result from chronic REM sleep deprivation due to REM sleep-related hypoventilation. If episodes of hypoventilation are more frequent or more severe in REM sleep, then the associated arousals will interrupt and reduce the amount of REM sleep. An SOREMP is one typical effect of REM sleep deprivation. We have previously reported a case in which hypoventilation did not result in apneic events but did produce severe oxygen desaturation associated with the hypoventilation during REM sleep. 2 This patient had SOREMPs (REM latencies of one and 11 minutes) on each of two nocturnal sleep recordings. Dr Vela-Bueno and associates' finding of severe hypoventilation and hypoxic

Circadian rhythms of sleep and wakefulness in mice: analysis using long-term automated recording of sleep.

Abstract: Circadian rhythms of wheel-running activity and polygraphically defined wakefulness, rapid-eye-movement (REM) sleep and non-REM (NREM) sleep were continuously observed in ten mice (Mus musculus) under both alternating light-dark (LD 12:12) and continuous darkness (DD) conditions. Sleep-wake state was determined automatically using a computer-based method that allowed continuous recordings of from 60 to 280 days in duration. The sleep-wake state percentages (of the circadian cycle) thus obtained were in substantial agreement with other estimates for this or similar strains and showed no significant difference between LD 12:12 (wake 54.3%, NREM sleep 38.1%, REM sleep 7.6%) and DD (wake 53.1%, NREM sleep 39.9%, REM sleep 7.0%) conditions. All 10 mice exhibited clear circadian rhythms in each of the three states and wheel-running activity under both lighting conditions for the entire duration of observation. Probability functions, computed using stationary sections of data from all 10 mice, showed distinct waveforms for all three states and wheel running. These waveforms were remarkably similar under entrained and free-running conditions. This documentation of sustained circadian rhythmicity in sleep-wake state throughout observations of unprecedented length contradicts the currently common assertion that circadian control of sleep state is weaker than that of activity.

Sleep patterns of sober chronic alcoholics.

Abstract: The somnopolygraphs of 26 sober chronic alcoholics were compared with those of an age-matched control group, after approximately 25 days of sobriety. The sleep efficiency index and latency to sleep on

Changes in sleep EEG architecture during the treatment of depressed patients with mianserin

Abstract: The effect of mianserin on sleep variables was studied in a single-blind non-controlled trial. Ten depressed hospital in-patients received placebo for one week and then mianserin 60 mg at night for four weeks. Acute changes seen on starting mianserin treatment included increases in sleep period time, total sleep time, sleep efficiency index, and stage II sleep, together with reductions in total time awake and latency for rapid eye movement sleep. The changes in sleep efficiency index, total time awake, stage II sleep, and latency for rapid eye movement sleep persisted over the duration of the study. Clinically, treatment with mianserin improved overall sleep pattern and ameliorated their depression.

Reappearance of electroencephalogram slow waves in extended sleep with delayed bedtime.

Abstract: A three-part study using prolonged nights of sleep was undertaken to verify Broughton's hypothesis of an approximate 12-h ultradrian rhythm of human slow wave sleep (SWS). Part I consisted of 2 8-h adaptation nights followed by a prolonged 15-h night of sleep with bedtime at midnight. A significant return of SWS occurred 12 h and 32 min after the first appearance of SWS. In part II, after 1 adaptation night, subjects were asked to sleep for 15 h but bedtime was delayed until 0400 h. A two-peak return of SWS was observed with a first significant return at 1228 h and a second significant return at 1745 h (i.e., 13 h and 32 min after the first appearance of SWS). In part III, bedtime was again delayed to 0400 h; but subjects were given 3 nights to adapt before the 15 h extended sleep. A single significant return of SWS was then observed at 1656 h, i.e., 12 h and 24 min after the first appearance with no peaks around 1200 h, thus exhibiting the same pattern as in part I. These results suggest that the return of SWS seen normally between 1200 and 1500 h is relatively well entrenched since it remained present in the extended night following sudden bedtime delay. It appears, moreover, that SWS does follow a bimodal 12-h rhythm, which is seen immediately upon extended delayed sleep and can be fully phase-shifted with habituation.

Slow wave sleep in elderly depressed, demented, and healthy subjects.

Abstract: The application of automated analysis in the measurement of sleep electroencephalogram delta activity allows a more precise temporal description of slow wave sleep changes in normal and pathological aging than do standard, all-night, slow wave sleep measures. Thus, with a baseline crossing technique, elderly depressives were shown to have a higher delta count per minute during the second NREM sleep period than did controls or demented subjects. This difference reflected greater activity per minute in the 2-3 Hz frequency band (75-200 microV).

On the explanation of short REM latencies in depression.

Abstract: Sleep in depression is characterized by the occurence of episodes of rapid eye movement (REM) sleep at sleep onset. The empirical foundations of three hypotheses about the origin of this phenomenon are examined: (1) A circadian rhythm hypothesis stating that sleep onset REM episodes (SOREMs) are the result of an abnormal phase-position of the REM sleep production cycle. (2) A REM sleep-slow wave sleep interaction hypothesis that attributes SOREMs to a low non-REM sleep propensity. (3) A circadian amplitude hypothesis, in which a flattening of the circadian arousal cycle is thought to be causally related to SOREMs. None of the hypotheses are found to be supported by firm empirical evidence.

Effects of body heating during sleep interruption.

Abstract: This study assessed the effects that elevating body temperature had on sleep structure in the third and fourth sleep cycles, cycles typically characterized by a high propensity for REM sleep and diminished levels of delta amplitude and incidence. The sleep of eight women and two men was interrupted for 30 min on each of 3 consecutive nights following an undisturbed adaptation night. The subjects were awakened each night following the end of the second REM sleep period. On 2 nights, subjects were immersed to midthorax in water at either 34 degrees C (TW condition) or 41 degrees C (HW condition) for 20 min. A third interruption without immersion (NW condition) was performed to provide a second type of baseline condition. The HW condition induced a mean tympanic temperature rise of 2.5 degrees C, that returned to baseline levels in approximately 60 min. Analysis of sleep patterns focused on the two sleep cycles following interruption. The mean of the two baseline conditions (TW + NW/2) was compared with the HW condition. Sleep onset latency, REM latency, REM duration, and eye movement activity in REM were unaffected by heating. Heating evoked increases in both total NREM and slow wave sleep, though these increases were delayed until the second cycle following sleep onset (i.e., appearing in the fourth, but not the third, NREM period). These were paralleled by increases in two objective measures of delta activity: integrated slow-wave amplitude (33% increase) and slow-wave density (10% increase).

Sleep mentation in the elderly.

Abstract: Mentation reports were elicited from NREM and REM sleep in 18 normal elderly females. Transcribed reports were analyzed for word count, visual and auditory imagery, intention, and affect. Comparison with similarly analyzed data from 23 young adult women revealed no differences between young and elderly in narrative length (either REM or NREM). Both groups showed longer narratives from REM awakenings. With narrative length controlled, NREM-REM differences in visual or auditory imagery, intention, or affect were non-existent in the young and very small in the elderly, findings that contradict earlier results but are consistent with more recent controlled studies in young adults. The elderly subjects showed strikingly less visual imagery than young subjects in both NREM and REM reports. Further studies are required to determine whether the decreased incidence of visual imagery in the elderly results from a response bias or from differences in the mechanisms of visual imagery production in sleep, waking, or both.

Post-Learning Paradoxical Sleep: A Critical Period When New Memory is Reactivated ?

Abstract: Though a state of deep sleep, it appears near to wakefulness in some of its characteristics ... Of course, such peculiarities of paradoxical sleep (PS) have puzzled many people and diverse hypotheses concerning its function have been proposed (Hennevin and Leconte, 1971). But, the only one which has been really tested is the hypothesis of an involvement of PS in memory processes.