Influence of lateral motion transfer on sleep.

This study examined the effects of motion of an artificial bed partner on the sleep of a real subject on the same mattress. A 240-lb eight-sided cylindrical roller served as the artificial bed partner. The roller was placed on one side of a king-size mattress and a normal adult slept on the other half. On experimental nights, the roller intermittently rocked back and forth for brief periods of time which in aggregate represented approximately 13% of total sleep time. On control nights, the roller was stationary. After an adaptation night in the laboratory, subjects spent two more nights in the sleep laboratory. The order of Roller On and Roller Off nights was random. 24 subjects were randomly assigned to sleep on the three surfaces. The three mattresses used in the study had different construction designs and in turn variable properties of motion transfer. Sleep variables were measured objectively by nocturnal polysomnography and subjectively by a postsleep questionnaire. Analysis of the data indicated that motion transferred laterally across a mattress was associated with a significant increase in Stage 1 sleep, and a significant decrease in Stage 3/4 sleep. Over-all, sleep efficiency, number of awakenings, and wakefulness after sleep onset did not show significant changes from control to experimental nights. The amount of change in sleep architecture, however, was more notable on the mattresses which transferred more motion. An implication of these findings is that motion transferred across the surface of a mattress, by lightening the depth of the sleep and thereby decreasing the auditory arousal threshold, can increase the potential for sleep disruption from environmental stimuli such as noise.     

The impact of prestimulus EEG frequency on auditory evoked potentials during sleep onset.

Auditory evoked potentials were recorded during wakefulness, Stage 1, and Stage 2 non-REM sleep using a three-tone auditory oddball paradigm. Stage 1 sleep was divided into trials preceded by alpha and those preceded by theta. A negative wave peaking at about 100 ms, N1, displayed a significant decrease in amplitude with the onset of Stage 2 sleep. A later N2 peaked at about 250 ms in the waking state. This changed into a sleep-specific negative wave peaking at 300 ms (N300) at the alpha-theta transition within Stage 1. The P300 displayed a similar shift to become a P450 in Stage 2 sleep. N550 was specific to Stage 2, and was larger in response to rare, rather than frequent stimuli. There was no evidence of any enhancement to relevant rare stimuli compared with irrelevant rare stimuli.     

Spatiotemporal variations of alpha and sigma band EEG in the waking-sleeping transition period

The aim of this study is to evaluate the spatiotemporal variation of alpha and sigma band EEGs during the waking-sleeping transition or hypnagogic period. Power and coherence from 7 EEG channels (Fp1, F7, Fz, C3, Pz, T5, O1) were studied using EEG records of the period of 5 min. before the onset of Stage 1 to 24 min. after the onset of Stage 1. The EEG spectra were computed for 4 frequency bands (alpha 1: 8.0-9.0 Hz, alpha 2: 9.5-11.0 Hz, alpha 3: 11.5-12.5 Hz, and sigma: 13.0-15.0 Hz). The power of alpha 1 and 2 bands initially started to decrease before the onset of Stage 1. Principal component analysis of the coherence yielded Generalized and Localized Components in each band. The Generalized Component was widespread across scalp areas, while the Localized Component was a restricted local area. The Generalized Components of alpha 1 and 2 bands reached stable levels of NREM sleep about 1 min. after the onset of Stage 1. The component of sigma band reached a stable level of NREM sleep about 0.6 min. before the onset of Stage 2, while the component of alpha 3 band reached a stable level of NREM sleep about 3.4 min. after the onset of Stage 2. These results suggest that the alpha-sigma band EEG structures during the waking-sleeping transition period may not be uniform across EEG bands and that the hypnagogic EEG changes may start before the onset of Stage 1 and continue for several minutes after the onset of Stage 2.     

Frontal electroencephalogram alpha asymmetry during sleep: stability and its relation to affective style

Electroencephalogram (EEG) alpha (8-12 Hz) asymmetries were collected from the mid-frontal and central regions during presleep wakefulness and Stage 1, Stage 2, and rapid eye movement (REM) sleep in 11 healthy right-handed participants who were free of psychiatric, neurological, and sleep problems. The authors found significant correlations between presleep wakefulness and different stages of sleep in the frontal, but not central, EEG alpha asymmetry measure. The strongest correlation was between presleep waking and REM sleep, replicating and extending relation earlier work to a normal population. The high degree of association between presleep waking and REM sleep may be a result of high cortical activation common to these states and may reflect a predisposition to different styles of emotional reactivity.     

Night terrors

Night terrors and nightmare had for years been equated terms. Early writers tended to ignore the differences. Even today with a clearer definition and understanding of these sleep disturbances, practitioners have been at a loss on how to ameliorate the very upsetting set of occurrences (to the patient as well as to the family). This paper briefly reviews some of the literature on Night Terrors and reports successes in the amelioration of this phenomenon.     

Sleep physiology and psychological aspects of the fibrositis (fibromyalgia) syndrome

Fibrositis (fibromyalgia) patients were compared with normal controls in terms of electrophysiology (EEG), self-report indicants of awakening, quality of sleep, behaviourally signalled awakenings, and Symptom Check List 90R (SCL-90R) scores. The results differentiated fibrositis patients from normal controls in terms of SCL-90R scores, with fibrositis patients showing significantly more psychopathology. Fibrositis patients had more alpha EEG sleep and less REM and Stage 1 sleep. They were better able to recall their behaviourally signalled awakenings the following morning and reported qualitatively less satisfying sleep than the normal controls. The alpha EEG sleep anomaly may reflect a vigilant arousal state during nocturnal sleep and result in the daytime experience of unrefreshing sleep, psychologic distress, that re-enforces the perpetuation of the sleep-related symptoms.     

Poor recall of eye-movement signals from Stage 2 compared to REM sleep: implications for models of dreaming

An ongoing assumption made by sleep researchers is that since dreams are more often recalled on awakening from rapid eye movement (REM) sleep, dreams must occur more often during this stage of sleep. An alternative hypothesis is that cognition occurs throughout sleep, but the recall of this mentation differs on awakening. When a dream is not reported on awakening, there is no method of establishing whether it did not happen or was forgotten. The aim of the present study was to investigate this issue using an eye movement (EM) signal verification technique. Participants were instructed to produce an EM signal whenever they heard a tone. Tones were presented at increasing volume during Stage 2 and REM sleep until EM signal verification was observed. Ninety seconds after signal verification, participants were awakened and asked if they remembered hearing the tone or responding with the EM signal. Such recollection of signal verified tone (SVT) presentations was significantly less after Stage 2 sleep (65%) compared to REM sleep (100%) presentations. Furthermore, SVT recall was significantly correlated with reported dream recall frequency, suggesting the same processes involved in recalling SVTs might also underlie dream recall.     

The toll of ethnic discrimination on sleep architecture and fatigue.

Most work on ethnicity tends to focus on daytime health rather than how aspects of ethnicity affect nighttime functioning. The current study examined how discrimination and ethnic identity relate to sleep architecture and fatigue in 37 African Americans and 56 Caucasian Americans. The authors conducted sleep monitoring with standard polysomnography. African Americans had less slow-wave sleep and reported more physical fatigue than did Caucasian Americans (ps < .05). The authors conducted path analyses to examine relationships between ethnic identity, perceived discrimination, sleep, and fatigue. Perceived discrimination mediated ethnic differences in Stage 4 sleep and physical fatigue. Individuals who reported experiencing more discrimination had less Stage 4 sleep and reported experiencing greater physical fatigue (ps < .05). Although ethnic identity did not mediate ethnic differences in sleep latency, there was a significant relationship between ethnic identity and sleep latency, indicating that individuals who felt more connected to their ethnic group had more difficulty falling asleep while in the hospital (p < .05). These observations suggest that the effects of stress related to one's ethnic group membership carry over into sleep.     

The mismatch negativity to frequency deviants during the transition from wakefulness to sleep.

This study examines the changes in the Mismatch Negativity during the transition from a waking, conscious state to one of sleep and unconsciousness. Auditory event-related potentials were recorded from eight participants during the sleep onset period. A 1,000 Hz-standard stimulus was presented every 600 ms. At random, on 20% of the trials, the standard was changed to either a large 2,000-Hz or a small 1,100-Hz deviant. During wakefulness, the large deviant elicited a larger, long-lasting MMN than the small deviant. Following the large deviant during relaxed wakefulness and Stage 2 sleep, the MMN continued to be elicited although it was reduced in amplitude. No significant MMN was recorded for either deviant in Stages 1 and slow wave sleep. The loss of consciousness therefore appears to have a marked effect on the MMN.     

Inside and outside the mind: The effects of age,organization, and access to external sources on retrieval of life events

Older and middle-aged adults recorded autobiographical events on one of two forms of a Personal History Calendar, organized either by year-of-occurrence or by life event category. In Experiment 1, calendars were completed in three stages. In Stage 1, subjects completed the calendar from memory (half were told to expect Stage 2). In Stage 2, each subject reviewed Stage 1 responses with his/her spouse. In Stage 3, subjects could consult external sources. The Event Calendar yielded the most complete Stage 1 recall only for the older group. The Year Calendar generally yielded the greatest number of events, but only when members of a couple did not expect Stage 2. In Experiment 2, subjects completed the calendars in one stage, during which they had access to external sources. The Year Calendar elicited more events than the Event Calendar, but only for older subjects. The results are discussed in terms of retrieval processes in autobiographical memory, and implicatons for survey-based research.     

Combining mindfulness meditation with cognitive-behavior therapy for insomnia: a treatment-development study

This treatment-development study is a Stage I evaluation of an intervention that combines mindfulness meditation with cognitive-behavior therapy for insomnia (CBT-I). Thirty adults who met research diagnostic criteria for Psychophysiological Insomnia (Edinger et al., 2004) participated in a 6-week, multi-component group intervention using mindfulness meditation, sleep restriction, stimulus control, sleep education, and sleep hygiene. Sleep diaries and self-reported pre-sleep arousal were assessed weekly while secondary measures of insomnia severity, arousal, mindfulness skills, and daytime functioning were assessed at pre-treatment and post-treatment. Data collected on recruitment, retention, compliance, and satisfaction indicate that the treatment protocol is feasible to deliver and is acceptable for individuals seeking treatment for insomnia. The overall patterns of change with treatment demonstrated statistically and clinically significant improvements in several nighttime symptoms of insomnia as well as statistically significant reductions in pre-sleep arousal, sleep effort, and dysfunctional sleep-related cognitions. In addition, a significant correlation was found between the number of meditation sessions and changes on a trait measure of arousal. Together, the findings indicate that mindfulness meditation can be combined with CBT-I and this integrated intervention is associated with reductions in both sleep and sleep-related arousal. Further testing of this intervention using randomized controlled trials is warranted to evaluate the efficacy of the intervention for this population and the specific effects of each component on sleep and both psychological and physiological arousal.     

Comparison of Motionlogger Watch and Actiwatch actigraphs to polysomnography for sleep/wake estimation in healthy young adults

Sleep/wake identification and sleep parameter estimates from Motionlogger Watch and Actiwatch-64 actigraphs were compared to polysomnography (PSG). Following one night of baseline sleep, 29 volunteers remained awake for 36 h, followed by 11 h of recovery sleep in the laboratory. Two sets of analyses were performed: (1) epoch-by-epoch agreement and discriminability index (d') calculations, and (2) sleep parameter concordance with repeated measures ANOVAs. Sensitivity (sleep identification), specificity (wake detection), and overall agreement with PSG, as well as d', were higher for the Motionlogger than for Actiwatch. Relative to PSG, the Actiwatch-estimated total sleep time and sleep efficiency were underestimated and the number of awakenings was overestimated for baseline and recovery; sleep latency was underestimated on the baseline night. On the other hand, the Motionlogger-estimated total sleep time and sleep efficiency estimates were underestimated, and the sleep latency was overestimated on recovery, versus PSG. Despite these misestimations, it was concluded that the Motionlogger provided nominally better agreement with PSG, and that actigraphy generally constitutes a reasonably reliable tool for producing objective measurements of sleep/wake, but that users should remain mindful of its limitations.     

Cognitive aspects of mental activity during sleep.

Upon nighttime experimental awakening of 27 subjects in four sleep conditions (sleep onset early; sleep onset late; Stage 2; and rapid eye movement, REM, sleep), 108 dream reports and their association reports were collected. Dream reports were analyzed for length (temporal units) and content categories (continuity; implausibility; presence of the dreamer [i.e., "the self"], a setting, characters). Associations were classified as episodic, abstract self-referred, and semantic memories. The two sets of results tend to show a basic homogeneity among mentation reports in the four sleep conditions considered. These findings are interpreted as supporting the hypothesis that the same cognitive mechanisms operate, at different levels of engagement, in dream generation rather than the hypothesis of multiple dream-generation systems dependent upon the physiological characteristics of the various sleep stages.     

Disqualified and qualified poor sleepers: subjective and objective variables

Sleep laboratory studies of patients complaining of insomnia have demonstrated discrepancies between subjective reports and electroencephalograph (EEG)-recorded measures. In our research studies on sleeping aids, 60% of the self-described poor sleepers who reported usual sleep latencies of at least 45 min did not meet the laboratory qualification criterion of a 30-min or longer sleep latency. To learn to predict who would qualify for our studies, we compared 30 laboratory-qualified poor sleepers (QPS) with 30 laboratory-disqualified poor sleepers (DPSs) on subjective report, mood, and all-night sleep laboratory variables. QPSs had significantly lower sleep efficiency and total sleep time in the laboratory, but these differences were due to the longer sleep latencies (50.7 +/- 27.8 min vs. 15.2 +/- 6.1 min) of the QPS group. QPSs and DPSs differed significantly in their morning estimates of their laboratory sleep latencies; as a group, QPSs gave an accurate estimate (51.6 +/- 27.8 min), but DPSs were significantly more likely to exaggerate their sleep latencies. Although we did not identify ways of predicting which poor sleepers would show sleep-onset insomnia in the sleep laboratory, we did find that, in this young, healthy population, there are poor sleepers who give an accurate report of a rather severe sleep-onset insomnia.     

3-minute smartphone-based and tablet-based psychomotor vigilance tests for the assessment of reduced alertness due to sleep deprivation

The psychomotor vigilance test (PVT) is widely used to measure reduced alertness due to sleep loss. Here, two newly developed, 3-min versions of the psychomotor vigilance test, one smartphone-based and the other tablet-based, were validated against a conventional 10-min laptop-based PVT. Sixteen healthy participants (ages 22–40; seven males, nine females) completed a laboratory study, which included a practice and a baseline day, a 38-h total sleep deprivation (TSD) period, and a recovery day, during which they performed the three different versions of the PVT every 3 h. For each version of the PVT, the number of lapses, mean response time (RT), and number of false starts showed statistically significant changes across the sleep deprivation and recovery days. The number of lapses on the laptop was significantly correlated with the numbers of lapses on the smartphone and tablet. The mean RTs were generally faster on the smartphone and tablet than on the laptop. All three versions of the PVT exhibited a time-on-task effect in RTs, modulated by time awake and time of day. False starts were relatively rare on all three PVTs. For the number of lapses, the effect sizes across 38 h of TSD were large for the laptop PVT and medium for the smartphone and tablet PVTs. These results indicate that the 3-min smartphone and tablet PVTs are valid instruments for measuring reduced alertness due to sleep deprivation and restored alertness following recovery sleep. The results also indicate that the loss of sensitivity on the 3-min PVTs may be mitigated by modifying the threshold defining lapses.     

Dreaming: cognitive processes during cortical activation and high afferent thresholds

The concepts of nonlocal, or distributed, cortical and cognitive activation are examined for their usefulness in describing the relations between sleep and waking neurocognitive processes. Changes in the pattern of distributed activation and inhibition of selected portions of sensory, cognitive, and motor decision modules account for the differences in imagery and thought across sleep and waking states in comparable environments. The massive inhibition of sensory and proprioceptive input to perceptual modules in Stage 1 REM sleep leaves the perceptual and cognitive modules, by default, with their own output as their sole input. Given this constraint, the activation of portions of the cortical structures that execute waking perceptual, cognitive and motor responses is necessary and sufficient to produce the imagery and thought of dreaming sleep. Connectionist models are introduced so that neurophysiological and cognitive concepts of distributed and local activation and inhibition can be translated into a common language, and in so doing, are used to simulate several processes fundamental to the production of imaginal thought and dreaming.     

Sleep arrangements and night waking at 6 and 12 months in relation to infants' stress‐induced cortisol responses

The objective of this short‐term longitudinal study was to examine the concurrent and prospective associations of infants' sleep arrangements and night waking with cortisol responses to an inoculation at 6 and 12 months, controlling for several key covariates. To our knowledge, this was the first study to concurrently and prospectively link proximity in sleep arrangements and night waking to physiological stress reactivity. A sample of 92 mother–infant dyads participated in the study when the infants were 6 and 12 months of age, although sample sizes were reduced for some analyses. Both proximal cosleeping arrangements and more frequent night wakings' were associated concurrently with an increased cortisol response to inoculations at both ages. Night waking at 6 months also was associated with a slightly increased cortisol response to inoculation at 12 months. Results aimed at exploring the direction of influence suggested that cosleeping and night waking may influence infant stress physiology rather than the reverse. Adaptive and maladaptive implications of infants' nocturnal experiences and greater stress‐induced cortisol responses are discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

"It's time, you must wake up now".

Seven subjects who claimed to be able to awake accurately from sleep at a predetermined time were required to awake in the sleep laboratory at 03:30 and 05:30 on two separate nights. Eight of the 12 spontaneous awakenings were within +/- 20 min. from the target time, and 8 awakenings were from REM sleep. The two best performing subjects were tested for additional 7 nights in the laboratory but accuracy deteriorated considerably with only 2 awakenings within +/- 20 min. from target time. Approximately 50% of all awakenings, however, were from REM sleep. It is concluded that some individuals are able to awake at predetermined times and that this ability might be dependent on motivational level and the sleep stage.     

Combined cognitive-behavioral therapy for fibromyalgia: Effects on polysomnographic parameters and perceived sleep quality

Background/Objective: Cognitive-behavioral therapy (CBT) is one of the first-line treatments in the management of fibromyalgia (FM) and it has been applied with considerable success to treat the psychological processes associated with pain and insomnia. We hypothesized that treating sleep and pain jointly with new combined modalities of CBT may offer greater sleep-related benefits to patients. Method: Thirty-nine female patients with FM and insomnia were randomly allocated to receive CBT centered on pain (CBT-P) or combined CBT focused on pain and insomnia (CBT-C). Participants were assessed at baseline and post-treatment with the Pittsburgh Sleep Quality Index and an ambulatory polysomnography.Results: Participants who received CBT-P showed increases in time in bed and total sleep time and decreases in light sleep, but there was no improvement in perceived sleep quality. Participants who received combined CBT-C showed more meaningful improvements related to refreshing sleep (i.e., higher sleep efficiency and less time awake and longer time in Stage 4 sleep), and these changes were concordant with a significant improvement in self-perceived sleep quality. Conclusions: This study suggests that new CBT-C approaches can improve insomnia-related clinical aspects.     

Development of sleep during monotonous stimulation as related to individual differences

This study was designed to examine whether the sleep-promoting effect of monotonous stimulation depends on individual differences in strength of the nervous system, as was suggested by Pavlov. Sixty male subjects were divided into three groups, depending on their score on the “strength of excitation” scale of the Strelau Temperament Inventory. Within each group, subjects were randomly assigned to be exposed to either a) a sequence of tones or b) “no tones” (i.e., a quiet room). Dependent variables were latencies to Sleep Stage 1 (SOL 1) and Sleep Stage 2 (SOL 2). The main effects of stimulation and strength of the nervous system were not statistically significant. However, there was a significant interaction between stimulation and strength for both dependent variables. “Weak” subjects tended to fall asleep more rapidly during monotonous stimulation, whereas the reverse was true of “strong” subjects. The results suggest that individual differences might play an important role in the development of sleep during monotonous stimulation.