Showing papers on "Non-rapid eye movement sleep published in 2001"

Emotional Memory Formation Is Enhanced across Sleep Intervals with High Amounts of Rapid Eye Movement Sleep

Abstract: Recent studies indicated a selective activation during rapid eye movement (REM) sleep of the amygdala known to play a decisive role in the processing of emotional stimuli. This study compared memory retention of emotional versus neutral text material over intervals covering either early sleep known to be dominated by nonREM slow wave sleep (SWS) or late sleep, in which REM sleep is dominant. Two groups of men were tested across 3-h periods of early and late sleep (sleep group) or corresponding retention intervals filled with wakefulness (wake group). Sleep was recorded polysomnographically. Cortisol concentrations in saliva were monitored at acquisition and retrieval testing. As expected, the amount of REM sleep was about three times greater during late than during early retention sleep, whereas a reversed pattern was observed for SWS distribution (P < 0.001). Sleep improved retention, compared with the effects of wake intervals (P < 0.02). However, this effect was substantial only in the late night (P < 0.005), during which retention was generally worse than during the early night (P < 0.02). Late sleep particularly enhanced memory for emotional texts. This effect was highly significant in comparison with memory for neutral texts (P < 0.01) and in comparison with memory after late and early wake intervals (P < 0.001). Cortisol concentration differed between early and late retention intervals but not between sleep and wake conditions. Results are consonant with a supportive function of REM sleep predominating late sleep for the formation of emotional memory in humans.

The REM Sleep-Memory Consolidation Hypothesis

Abstract: It has been hypothesized that REM (rapid eye movement) sleep has an important role in memory consolidation. The evidence for this hypothesis is reviewed and found to be weak and contradictory. Animal studies correlating changes in REM sleep parameters with learning have produced inconsistent results and are confounded by stress effects. Humans with pharmacological and brain lesion-induced suppression of REM sleep do not show memory deficits, and other human sleep-learning studies have not produced consistent results. The time spent in REM sleep is not correlated with learning ability across humans, nor is there a positive relation between REM sleep time or intensity and encephalization across species. Although sleep is clearly important for optimum acquisition and performance of learned tasks, a major role in memory consolidation is unproven.

Autonomic activity during human sleep as a function of time and sleep stage

Abstract: While there is a developing understanding of the influence of sleep on cardiovascular autonomic activity in humans, there remain unresolved issues. In particular, the effect of time within the sleep period, independent of sleep stage, has not been investigated. Further, the influence of sleep on central sympathetic nervous system (SNS) activity is uncertain because results using the major method applicable to humans, the low frequency (LF) component of heart rate variability (HRV), have been contradictory, and because the method itself is open to criticism. Sleep and cardiac activity were measured in 14 young healthy subjects on three nights. Data was analysed in 2-min epochs. All epochs meeting specified criteria were identified, beginning 2 h before, until 7 h after, sleep onset. Epoch values were allocated to 30-min bins and during sleep were also classified into stage 2, slow wave sleep (SWS) and rapid eye movement (REM) sleep. The measures of cardiac activity were heart rate (HR), blood pressure (BP), high frequency (HF) and LF components of HRV and pre-ejection period (PEP). During non-rapid eye movement (NREM) sleep autonomic balance shifted from sympathetic to parasympathetic dominance, although this appeared to be more because of a shift in parasympathetic nervous system (PNS) activity. Autonomic balance during REM was in general similar to wakefulness. For BP and the HF and LF components the change occurred abruptly at sleep onset and was then constant over time within each stage of sleep, indicating that any change in autonomic balance over the sleep period is a consequence of the changing distribution of sleep stages. Two variables, HR and PEP, did show time effects reflecting a circadian influence over HR and perhaps time asleep affecting PEP. While both the LF component and PEP showed changes consistent with reduced sympathetic tone during sleep, their pattern of change over time differed.

Beta/Gamma EEG activity in patients with primary and secondary insomnia and good sleeper controls

Abstract: Study Objective: Several studies have shown that patients with insomnia exhibit elevated levels of Beta EEG activity (14-35 Hz) at or around sleep onset and during NREM sleep. In this study, we evaluated 1) the extent to which high frequency EEG activity is limited to the 14-32 Hz domain, 2) whether high frequency EEG activity (HFA) is associated with discrepancies between subjective and PSG measures of sleep continuity, and 3) the extent to which high frequency EEG activity occurs in patients with primary, as opposed to secondary, insomnia. Design: Three groups (n=9 per group) were compared: Primary Insomnia, Insomnia secondary to Major Depression, and Good Sleeper Controls. Groups were matched for age, sex and body mass. Average spectral profiles were created for each NREM cycle after removing waking and movement epochs and epochs containing micro- or mini-arousals. Setting: Sleep Research Laboratory Patients or Participants: Patients with primary and secondary insomnia Interventions: N/A Measurements and Results: Subjects with Primary Insomnia exhibited more average NREM activity for Beta-1 (14-20Hz), Beta-2 (20-35Hz) and Gamma activity (35-45Hz) than the other two groups (p.<.01) Group differences were also suggestive for Omega activity (45.0-125Hz) (p.<.10), with MDD subjects tending to exhibit more activity than the other groups. Correlational analyses revealed that average NREM Beta-1 and Beta-2 activity tended to be negatively correlated with subjective-objective discrepancy measures for total sleep time and sleep latency. Conclusions: Our results confirm that Beta activity is increased in Primary Insomnia. In addition, our data suggest that high frequency activity in oatients with Primary Insomnia is limited to the Beta/Gamma range (14-45 Hz), and is neqativelv associated with the perception of sleep.

Sleeping brain, learning brain. The role of sleep for memory systems

Abstract: The hypothesis that sleep participates in the consolidation of recent memory traces has been investigated using four main paradigms: (1) effects of post-training sleep deprivation on memory consolidation, (2) effects of learning on post-training sleep, (3) effects of within sleep stimulation on the sleep pattern and on overnight memories, and (4) re-expression of behavior-specific neural patterns during post-training sleep. These studies convincingly support the idea that sleep is deeply involved in memory functions in humans and animals. However, the available data still remain too scarce to confirm or reject unequivocally the recently upheld hypothesis that consolidations of non-declarative and declarative memories are respectively dependent upon REM and NREM sleep processes.

Distribution of partial seizures during the sleep--wake cycle: differences by seizure onset site.

Abstract: Objective: To evaluate the effects of sleep on partial seizures arising from various brain regions. Methods: The authors prospectively studied 133 patients with localization-related epilepsy undergoing video-EEG monitoring over a 2-year period. Seizure type, site of onset, sleep/wake state at onset, duration, and epilepsy syndrome diagnosis were recorded. Periorbital, chin EMG, and scalp/sphenoidal electrodes were used. A subset of 34 patients underwent all-night polysomnography with scoring of sleep stages. Results: The authors analyzed 613 seizures in 133 patients. Forty-three percent (264 of 613) of all partial seizures began during sleep. Sleep seizures began during stages 1 (23%) and 2 (68%) but were rare in slow-wave sleep; no seizures occurred during REM sleep. Temporal lobe complex partial seizures were more likely to secondarily generalize during sleep (31%) than during wakefulness (15%), but frontal lobe seizures were less likely to secondarily generalize during sleep (10% versus 26%; p Conclusions: Partial-onset seizures occur frequently during NREM sleep, especially stage 2 sleep. Frontal lobe seizures are most likely to occur during sleep. Patients with temporal lobe seizures have intermediate sleep seizure rates, and patients with seizures arising from the occipital or parietal lobes have rare sleep-onset seizures. Sleep, particularly stage 2 sleep, promotes secondary generalization of temporal and occipitoparietal, but not frontal, seizures. These findings suggest that the hypersynchrony of sleep facilitates both initiation and propagation of partial seizures, and that effects of sleep depend in part on the location of the epileptic focus.

The relationship between fatigue and sleep in cancer patients: a review.

Abstract: Fatigue is a major complaint among cancer patients, yet it is unknown whether cancer-related fatigue experienced during the day relates to sleep/wake cycles or to the quality and quantity of sleep obtained at night. Although it is not well defined or well understood at present, cancer-related fatigue is generally regarded as a form of tiredness that does not improve following rest or sleep. Objectively recorded sleep and biological rhythms have not been well investigated in these patients, but it appears that most cancer patients may in fact not be getting a good night's sleep. Evidence is accumulating that sleep is often disturbed in cancer patients, probably owing to a variety of causes. We posit that some degree of cancer-related fatigue experienced during the day may relate to sleep/wake cycles or to the quality and quantity of sleep obtained at night. Different components or dimensions of fatigue (physical, attentional/cognitive, emotional/affective, etc.) are probably associated in some way with disrupted sleep and desynchronized sleep/wake rhythms. These associations may change in measurable ways prior to treatment, during treatment and after treatment completion. In cancer patients, as in other medically ill patients, sleep that is inadequate or unrefreshing may be important not only to the expression of fatigue, but to the patients' quality of life and their tolerance to treatment, and may influence the development of mood disorders and clinical depression. This review summarizes the state of the literature on fatigue, sleep and circadian rhythms.

Interactions between sleep and epilepsy.

Abstract: Sleep is one of the best-documented factors influencing the expression of seizures and interictal discharges. Janz studied the relation between seizures and the sleep/wake cycle and divided the epilepsies into three categories: nocturnal, awakening, and diffuse. Since then, the effect of sleep on the ictal and interictal manifestations of epilepsy has been studied extensively. Many seizures are activated by sleep or arousal from sleep. Interictal discharges are also seen more commonly during sleep, with the greatest activation seen during nonrapid eye movement sleep. Sleep not only increases the frequency of epileptiform abnormalities, but also may alter their morphology and distribution. Sleep deprivation also facilitates both epileptiform abnormalities and seizures. Seizures, on the other hand, also impact sleep. Epileptic patients demonstrate multiple sleep abnormalities, including an increased sleep latency, fragmented sleep, increased awakenings and stage shifts, and an increase in stages 1 and 2 of nonrapid eye movement sleep. These disturbances may in turn be modulated by antiepileptic treatment. This review summarizes the interactions between sleep and epilepsy, including the timing of seizures during the sleep/wake cycle, the influence of sleep on various seizure disorders, the effects of sleep deprivation, and the changes in sleep patterns caused by seizures and their treatment.

Night Waking, Sleep-Wake Organization, and Self-Soothing in the First Year of Life

Abstract: Few objective data are available regarding infants' night waking behaviors and the development of self-soothing during the first year of life. This cross-sectional study examined 80 infants in one of four age groups (3, 6, 9, or 12 mo) for four nights by using videosomnography to code nighttime awakenings and parent-child interactions. A large degree of variability was observed in parents' putting the infant to bed awake or asleep and in responding to vocalizations after nighttime awakenings. Most infants woke during the night at all ages observed. Younger infants tended to require parental intervention at night to return to sleep, whereas older infants exhibited a greater proportion of self-soothing after nighttime awakenings. However, even in the 12-month-old group, 50% of infants typically required parental intervention to get back to sleep after waking. Results emphasize the individual and contextual factors that effect the development of self-soothing behavior during the first year of life.

Age-related modifications of NREM sleep EEG: from childhood to middle age.

Abstract: This study investigated the modifications in non-rapid eye movement (NREM) sleep electroencephalogram (EEG) power in 54 subjects, from children to middle-aged adults. Spectral analyses were performed on 5 h of NREM sleep. A marked decrease of absolute slow-wave activity (SWA) was observed with increasing age; children had significantly more SWA than adolescents, young and middle-aged adults. The decline of SWA across the night seems to level off with increasing age, suggesting an age-related attenuation of homeostatic sleep pressure. Absolute theta power was higher for children compared with the other three groups, and adolescents had more theta power than young and middle-aged adults. In comparison to young and middle-aged adults, alpha power was higher for children and adolescents. Children and adolescents had more sigma power than middle-aged adults. Absolute beta power was higher for children than for the other age groups. Therefore, the major alterations of NREM sleep EEG occurring between childhood and middle age are not restricted to SWA, but encompassed the theta, alpha, sigma and beta frequency bands.

Sleep during Ramadan intermittent fasting.

Abstract: During the month of Ramadan intermittent fasting, Muslims eat exclusively between sunset and sunrise, which may affect nocturnal sleep. The effects of Ramadan on sleep and rectal temperature (Tre) were examined in eight healthy young male subjects who reported at the laboratory on four occasions: (i) baseline 15 days before Ramadan (BL); (ii) on the eleventh day of Ramadan (beginning of Ramadan, BR); (iii) on the twenty-fifth day of Ramadan (end of Ramadan, ER); and (iv) 2 weeks after Ramadan (AR). Although each session was preceded by an adaptation night, data from the first night were discarded. Polysomnography was taken on ambulatory 8-channel Oxford Medilog MR-9000 II recorders. Standard electroencephalogram (EEG), electro-oculogram (EOG) and electromyogram (EMG) recordings were scored visually with the PhiTools ERA. The main finding of the study was that during Ramadan sleep latency is increased and sleep architecture modified. Sleep period time and total sleep time decreased in BR and ER. The proportion of non-rapid eye movement (NREM) sleep increased during Ramadan and its structure changed, with an increase in stage 2 proportion and a decrease in slow wave sleep (SWS) duration. Rapid eye movement (REM) sleep duration and proportion decreased during Ramadan. These changes in sleep parameters were associated with a delay in the occurrence of the acrophase of Tre and an increase in nocturnal Tre during Ramadan. However, the 24-h mean value (mesor) of Tre did not vary. The nocturnal elevation of Tre was related to a 2-3-h delay in the acrophase of the circadian rhythm. The amplitude of the circadian rhythm of Tre was decreased during Ramadan. The effects of Ramadan fasting on nocturnal sleep, with an increase in sleep latency and a decrease in SWS and REM sleep, and changes in Tre, were attributed to the inversion of drinking and meal schedule, rather than to an altered energy intake which was preserved in this study.

Age-related increase in awakenings: impaired consolidation of nonREM sleep at all circadian phases.

Abstract: Study objectives (1) To assess the circadian and sleep-dependent regulation of the frequency and duration of awakenings in young and older people; (2) to determine whether age-related deterioration of sleep consolidation is related to an increase in the frequency or duration of awakenings; (3) to determine whether pre-awakening sleep structure is preferentially enriched by REM sleep or nonREM sleep and (4) to determine whether sleep structure prior to awakenings is affected by age. Design Between age-group comparison of sleep consolidation and sleep structure preceding awakenings. Setting Environmental Scheduling Facility, General Clinical Research Center. Participants Eleven healthy young men (21-30 years) and 13 older healthy men (n=9) and women (n=4) (64-74 years). Interventions Forced desynchrony between the sleep-wake cycle and circadian rhythms by scheduling of the rest-activity cycle to 28-h for 21-25 cycles. Measurements and results Circadian and sleep-dependent regulation of the frequency and duration of awakenings and of sleep structure preceding awakenings were assessed in 482 sleep episodes (9h 20 min each). The circadian modulation of wakefulness within sleep episodes was primarily related to a variation in the duration of awakenings. In contrast, the age-related reduction of sleep consolidation was primarily related to an increase in the frequency of awakenings. Whereas in both young and older subjects pre-awakening sleep contained more REM sleep than overall sleep, this enrichment of REM sleep (i.e., the gating of wakefulness by REM sleep) was diminished in older people. In older people, preawakening sleep contained more nonREM sleep and stage two sleep in particular, than in young people. Conclusions At all circadian phases, the age-related reduction of sleep consolidation is primarily related to a reduction in the consolidation of nonREM sleep.

Dynamics of frontal EEG activity, sleepiness and body temperature under high and low sleep pressure.

Abstract: The impact of sleep deprivation (high sleep pressure) vs sleep satiation (low sleep pressure) on waking EEG dynamics, subjective sleepiness and core body temperature (CBT) was investigated in 10 young volunteers in a 40 h controlled constant posture protocol. The differential sleep pressure induced frequency-specific changes in the waking EEG from 1‐ 7 Hz and 21‐25 Hz. Frontal low EEG activity (FLA, 1‐7 Hz) during sleep deprivation exhibited a prominent increase as time awake progressed, which could be significantly attenuated by sleep satiation attained with intermittent naps. Subjective sleepiness exhibited a prominent circadian regulation during sleep satiation, with virtually no homeostatic modulation. These extremely different sleep pressure conditions were not reflected in significant changes of the CBT rhythm. The data demonstrate that changes in FLA during wakefulness are to a large extent determined by the sleep-wake dependent process with little circadian modulation, and reflect differential levels of sleep pressure in the awake subject. NeuroReport 12:2277‐2281 & 2001 Lippincott Williams & Wilkins.

Melatonin therapy for REM sleep behavior disorder

Abstract: Rapid eye movement sleep behavior disorder (RBD) is a parasomnia with clinical symptoms that include punching, kicking, yelling and leaping out of bed in sleep. Polysomnographic (PSG) finding showed REM sleep without muscle atonia. Clonazepam is generally used for treating RBD symptoms but melatonin was reported to be effective so we reconfirmed the effect of melatonin on RBD patients in the present study. We used melatonin (3–9 mg/day) which could ameliorate problem sleep behaviors remarkably, as well as %tonic activity in PSG variables. In the present study, melatonin was reconfirmed to be effective in RBD symptoms, especially for patients with low melatonin secretion, while its mechanism was not clearly known in the present study.

From slow waves to sleep homeostasis: new perspectives.

Abstract: EEG slow waves are the epitome of deep nonREM sleep. The level of slow-wave activity (SWA; defined as spectral power in the 0.5-4.5 Hz band) in the initial part of sleep is determined by prior sleep and waking, and thereby represents a marker of a homeostatic sleep regulating process (Process S). Models based on SWA were successful in simulating sleep architecture in a variety of experimental protocols. SWA is an exceptional sleep variable in that it is little influenced by circadian phase and variations of the photoperiod. There is recent evidence that it is not waking per se but the absence of sleep, which engenders a rise in sleep propensity. Thus animals emerging from the hypometabolic states of hibernation or daily torpor exhibit an increase in SWA akin to sleep deprivation. Recent human studies showed SWA to be a marker of a local, use-dependent facet of sleep. Selective activation of specific cortical areas during waking enhanced SWA over the activated region during sleep. A frontal predominance of power in the 2-Hz band was documented in the initial part of a normal sleep episode. Sleep homeostasis may be a valuable concept for exploring the evolutionary origin of sleep. Thus 'rest homeostasis' has been demonstrated in invertebrate species, and the search for homologies of rest and sleep on a molecular genetic level has begun. Conceptualizing and characterizing sleep as a regulated process may eventually shed light on its function.

Basal forebrain acetylcholine release during REM sleep is significantly greater than during waking

Abstract: Cholinergic neurons of the basal forebrain supply the neocortex with ACh and play a major role in regulating behavioral arousal and cortical electroencephalographic activation. Cortical ACh release is greatest during waking and rapid eye movement (REM) sleep and reduced during non-REM (NREM) sleep. Loss of basal forebrain cholinergic neurons contributes to sleep disruption and to the cognitive deficits of many neurological disorders. ACh release within the basal forebrain previously has not been quantified during sleep. This study used in vivo microdialysis to test the hypothesis that basal forebrain ACh release varies as a function of sleep and waking. Cats were trained to sleep in a head-stable position, and dialysis samples were collected during polygraphically defined states of waking, NREM sleep, and REM sleep. Results from 22 experiments in four animals demonstrated that means ± SE ACh release (pmol/10 min) was greatest during REM sleep (0.77 ± 0.07), intermediate during waking (0.58 ± 0.03), and lowest during NREM sleep (0.34 ± 0.01). The finding that, during REM sleep, basal forebrain ACh release is significantly elevated over waking levels suggests a differential role for basal forebrain ACh during REM sleep and waking.

Temporal and stagewise distribution of high frequency EEG activity in patients with primary and secondary insomnia and in good sleeper controls

Abstract: In the present study, we evaluate the temporal and stagewise distribution of high frequency EEG activity (HFA) in primary and secondary insomnia. Three groups (n=9 per group) were compared: primary insomnia (PI), Insomnia secondary to major depression (MDD), and good sleeper controls (GS). Groups were matched for age, sex and body mass. Average spectral profiles were created for each sleep epoch. Grand averages were created for each NREM cycle and each stage of sleep after removing waking and movement epochs and epochs containing micro or miniarousals. It was found that HFA (in terms of relative power) tends to increase across NREM cycles, occurs maximally during stage 1 and during REM sleep, and that both these effects are exaggerated in patients with PI. In addition, HFA was found to be inversely associated with Delta activity and the three groups in our study appear to exhibit characteristic Delta/Beta patterns. Our data are consistent with the perspective that HFA is related to CNS arousal to the extent that Beta/Gamma activity occurs maximally during shallow stages of sleep and maximally in subjects with PI.

Postoperative sleep disturbance: influences of opioids and pain in humans.

Abstract: Study objectives To test the hypothesis that opioids and pain contribute independently to postoperative sleep disturbance, 10 women undergoing surgery requiring a low abdominal incision for treatment of benign gynecologic conditions were randomized to receive either epidural opioid (fentanyl) (n=6) or epidural local anesthetic (bupivacaine) (n=4) for intraoperative and postoperative analgesia. Design N/A. Setting N/A. Patients or participants N/A. Interventions N/A. Measurements Polysomnography was performed in a standard patient room on the preoperative and first three postoperative nights. Pain at rest and with coughing was evaluated using a visual-analogue pain scale each evening and morning. Results On the first postoperative night, rapid eye movement (REM) sleep was abolished in all patients. On the third postoperative night, the mean +/- SE REM sleep time increased significantly (p=.003) to 9.8% +/- 3.1% in the fentanyl group, and 12.9% +/- 3.8% in the bupivacaine group. Conversely, light non-REM (NREM) sleep (%stage 1 + %stage 2) was higher on the first postoperative night and significantly lower on the third postoperative night (p=0.011). Between group comparison revealed only that the mean % slow-wave sleep (SWS) in the fentanyl group (6.0%, 2.0%, and 14.7%) was different from the bupivacaine group (7.8%, 9.1%, and 10.6%) in the postoperative period after adjusting for the preoperative night % SWS (p=0.021). Pain was well controlled in all patients, but was slightly better controlled in the fentanyl group than in the bupivacaine group on postoperative night 2 (p=0.024). There was no statistically significant association between pain score and any polysomnographically defined stage. Conclusion Postoperative patients suffer a profound sleep disturbance even when opioids are avoided and pain is well controlled.

Brain-mind states: I. Longitudinal field study of sleep/wake factors influencing mentation report length.

Abstract: Study objectives To collect and analyze reports of mental activity across sleep/wake states. Design Mentation reports were collected in a longitudinal design by combining our Nightcap sleep monitor with daytime experience sampling techniques. Reports were collected over 14 days and nights from active and quiet wake, after instrumental awakenings at sleep onset, and after both spontaneous and instrumental awakenings from REM and NREM sleep. Setting All reports were collected in the normal home, work and school environments of the subjects. Participants Subjects included 8 male and 8 female undergraduate students (19-26 years of age). Interventions N/A. Measurements and results A total of 1,748 reports, averaging 109 per subject, were collected from active wake across the day (n=894), from quiet wake in the pre-sleep onset period (n=58), from sleep onset (n=280), and from later REM (n=269) and nonREM (n=247) awakenings. Median report lengths varied more than 2-fold, in the order REM > active wake > quiet wake > NREM = sleep onset. The extended protocol allowed many novel comparisons between conditions. In addition, while spontaneous REM reports were longer than those from forced awakenings, the difference was explained by the time within the REM period at which the awakenings occurred. Finally, intersubject differences in REM report lengths were correlated with similar differences in waking report lengths. Conclusions The use of the Nightcap sleep monitoring system along with waking experience sampling permits a more complete sampling and analysis of mental activity across the sleep/wake cycle than has been previously possible.

A model of sleep-disordered breathing in the C57BL/6J mouse.

Abstract: To investigate the pathophysiological sequelae of sleep-disordered breathing (SDB), we have developed a mouse model in which hypoxia was induced during periods of sleep and was removed in response ...