Non-rapid eye movement sleep

About: Non-rapid eye movement sleep is a research topic. Over the lifetime, 8661 publications have been published within this topic receiving 389465 citations. The topic is also known as: NREM.

Scoring transitions to REM sleep in rats based on the EEG phenomena of pre-REM sleep: an improved analysis of sleep structure.

Abstract: Algorithms for scoring sleep/waking states and transitions to REM sleep (NRTs) in rats are presented and validated. Both algorithms are based on electroencephalographic (EEG) power in delta (0.5-4.0 Hz), theta (6-9 Hz) and sigma (10-14 Hz) frequency bands, and electromyogram (EMG) intensity. Waking is scored when EMG intensity is high or (sigma power).(theta power) is low. Nonrapid eye movement (NREM) sleep is scored in nonwaking epochs having high (delta power)/(theta power). Rapid eye movement (REM) sleep is scored in nonwaking epochs having low (delta power)/(theta power). NRTs are identified by the EEG phenomena of the pre-REM sleep phase of NREM sleep. Algorithms are validated by comparison with records scored independently by two investigators based on visual examination of EEGs and EMGs. The sleep/waking-state scoring algorithm produces greater than 90% agreement with visual scoring. The NRT-scoring algorithm produces 88-92% agreement with visual scoring. Scoring NRTs based on the phenomena of the pre-REM sleep phase of NREM sleep, instead of relying solely on REM sleep expression for identification of REM sleep onset, reveals a significant population of brief REM sleep episodes that are ignored by most sleep cycle analyses and allows independent quantification of REM sleep timing and maintenance.

Sleep disorders in the elderly.

Abstract: Nearly half of older adults report difficulty initiating and maintaining sleep. With age, several changes occur that can place one at risk for sleep disturbance including increased prevalence of medical conditions, increased medication use, age-related changes in various circadian rhythms, and environmental and lifestyle changes. Although sleep complaints are common among all age groups, older adults have increased prevalence of many primary sleep disorders including sleep-disordered breathing, periodic limb movements in sleep, restless legs syndrome, rapid eye movement (REM) sleep behaviour disorder, insomnia, and circadian rhythm disturbances. The present review discusses age-related changes in sleep architecture, aetiology, presentation, and treatment of sleep disorders prevalent among the elderly and other factors relevant to ageing that are likely to affect sleep quality and quantity.

Effects of Sleep Deprivation on Behaviour, Subsequent Sleep, and Dreaming

Abstract: The EEG and eye-movements during nocturnal sleep were recorded from six males on four base-line nights and four recovery nights following 108 hours of sleep deprivation. On the first recovery night there was a significant increase in the mean percentage of total sleep time during which EEG signs of deep sleep were present, associated with a significant decrease in the mean percentage of total sleep time spent in dreaming (determined by duration of rapid eye movement periods) on comparison with the base-line nights. On the second recovery night there was a significant increase in mean dream time percentage compared with that on the base-line nights. The results are discussed in relation to theories of a “need” for dreaming. Hallucinations, paranoid delusions and other abnormal behaviour during sleep deprivation are described.

Fast sleep spindle (13-15 hz) activity correlates with sleep-dependent improvement in visuomotor performance.

Abstract: MASTERY OF MOTOR SKILLS GENERALLY REQUIRES CONSIDERABLE REPETITION AND PRACTICE OVER EXTENDED PERIODS OF TIME. HOWEVER, prolonged and repeated training sessions can result in short-term performance decrements due to fatigue, decreased motivation, and reduced attention.1 One night of sleep has been shown to enhance motor skills,2,3 suggesting that sleep may facilitate “reconsolidation” of procedural memory. Tamaki et al2 compared the effects of sleep and wakefulness during the retention period for newly acquired versus preacquired visuomotor skill. Using a modified version of the classic mirror-tracing task, they found that the time taken to perform a newly acquired visuomotor skill improved by approximately 8.4 seconds (24.9%) when practice sessions were followed by sleep. However, no significant improvement was observed in subjects who remained awake following the practice sessions (−0.3 seconds, −2.0%). This suggests that posttraining sleep facilitates the learning a newly acquired visuomotor skill. Sleep spindles are among the most prominent characteristics of non-rapid eye movement (NREM) sleep. Sleep spindles appear mainly during NREM stage 2 sleep and are one of the defining characteristics of this stage. It has previously been determined that the number of spindles (or sigma power) gradually increases over consecutive sleep cycles within a night, reaching asymptote around the third or fourth cycle.4–7 Steriade and colleagues have extensively studied the mechanisms underlying sleep spindles and have found that reticular thalamic nucleus, thalamocortical neurons, and cortical pyramidal cells are involved.8 Several recent reports have suggested that sleep spindles contribute to memory enhancement during sleep. Schiffelhoz and Aldenhoff9 demonstrated that rats experience a greater amount of pre-rapid eye movement (REM) sleep (the intermediate sleep stage with high spindle activity) following exposure to a new environment. Several studies have also demonstrated that hippocampal ripple (140- to 200-Hz) activity is temporally correlated with cortical spindle activity (in prefrontal and somatosensory regions) in both mice and rats, further suggesting that sleep spindles may facilitate (or at least reflect) memory-related processes such as plasticity.10,11 Similarly, it has been suggested that slow waves may somewhat indirectly facilitate memory processes during sleep by virtue of influencing the temporal pattern of spindle activity in a manner that facilitates induction of neural plasticity in the cortex.12 Evidence linking spindle activity and memory is substantial. Using an odor-reward association task, Eschenko et al13 found that spindle density increases after both learning and retrieval in rats. Similarly, in studies on humans, the density of sleep spindles was found to be significantly higher during sleep after a paired-association task than after a nonmemory control task.14 Clemens et al15 demonstrated that overnight verbal memory retention after a face-name association test was highly correlated with number of sleep spindles. Although the studies linking spindle activity and declarative memory are compelling, thus far, few have reported a significant relationship between procedural memory and sleep-spindle activity. One exception is a study by Fogel and Smith,16 who found increased spindle (12–16 Hz) density (the number of spindles per minute) after the participants had learned 4 types of motor tasks. Together, these various studies suggest that sleep-spindle activity reflects sleep-dependent facilitation of both hippocampus-dependent declarative memory and hippocampus-independent procedural memory processes. Less clear is the issue of whether sleep-spindle subtypes are differentially associated with memory enhancement. In some studies that have qualitatively and quantitatively analyzed electroencephalogram activity, sleep spindles have been grouped into 2 subtypes. The first is the slow spindle, with a frequency of approximately 12 Hz and a predominantly fronto-central scalp distribution. The second is the fast spindle, with a frequency of approximately 14 Hz and predominantly centro-parietal scalp distribution.6,7,17,18 Importantly, the temporal distribution of these 2 types of spindles also differs during sleep. Slow spindles tend to predominate in the early part of the night, whereas fast spindles tend to appear later.6,7,18 For both types of sleep spindles, equivalent dipole sources near the thalamus have been estimated.19 The orientation of the equivalent dipole of the fast spindle is in the centro-parietal direction, whereas that of the slow spindle is in the frontal direction. Sleep-spindle types also differ with respect to subsequent EEG activity: Immediately following a fast spindle, activity in the delta-theta band (0.78–7.42 Hz) is enhanced in the centro-parietal areas, while slow spindles tend to be followed by enhanced activity in fronto-central areas.4 Given the different spatial and temporal distribution of fast- and slow-spindle subtypes, it is possible that they also play different roles in sleep-related memory processes. To date, there is only 1 study (by Plihal and Born28) that suggests (albeit indirectly) that procedural memory may be differentially enhanced by fast spindles, since they found, using a classic mirror-tracing task, that the latter half of nighttime sleep is required for the consolidation of procedural memory. Although they suggested that this may have been associated with increased REM sleep in the latter half of the night, fast sleep spindles also tend to predominate during this portion of the night. It was therefore hypothesized that slow and fast spindles may differentially reflect enhancement of different types of memory, with fast-spindle activity selectively associated with enhancement of procedural memory. Accordingly, the aim of the present study was to determine whether sleep-mediated facilitation of performance on a mirror-tracing task is differentially associated with fast- versus slow-spindle activity during nighttime sleep.

Sleep in rheumatoid arthritis: a comparison with healthy subjects and studies of sleep/wake interactions.

Abstract: Sleep complaints are frequent in patients with rheumatoid arthritis (RA) and sleep disturbances may contribute to pain and other daytime complaints. The aims of the current study were to compare ambulatory sleep recordings from consecutively selected patients with RA to those obtained in healthy controls, and to study the relationships between sleep structure and clinical symptoms. Sleep recordings were obtained from 41 out-patients with RA and 19 matched controls. All had clinical examinations and completed different questionnaires. Recordings were scored traditionally and, moreover, the electroencephalography (EEG) was subjected to frequency analysis. For the study of sleep-wake interactions in the patients, a graphical chain model was used. The patients had many sleep-related complaints. An increase in the number of periodic movements of the legs (PML) during sleep was seen in comparison with controls, but otherwise only minor differences were observed in classical sleep stages. Data from frequency analysis showed an increase in alpha (8-12 Hz)-EEG activity in sleep stages non-rapid eye movement (NREM) 2-4 in most sleep cycles. The statistical model demonstrated a complex but independent correlation between morning stiffness, pain and joint tenderness on the one hand, and awakenings, stage NREM2, slow-wave sleep and stage REM on the other, probably reflecting a relationship between sleep patterns and pain in RA. In conclusion, only the increase in PML and alpha-EEG activity distinguished the sleep in RA patients from that of healthy controls. However, the demonstrated interaction between daytime complaints and sleep patterns may increase the understanding and treatment of the disease. In future research, graphical chain models may improve our understanding of complex relationships between multiple variables.