Behavioural therapy for shift work disorder improves shift workers' sleep, sleepiness and mental health: A pilot randomised control trial.

The present study evaluates the efficacy of behavioural therapy adapted for shift work disorder with a randomised control design in a healthcare population. Forty-three night shift workers (m. age: 34 years; 77% women) experiencing shift work disorder were randomised to either the behavioural therapy for shift work disorder (BT-SWD) or a waiting-list control group offered after the waiting period. Participants completed questionnaires on insomnia, sleepiness and mental health pre- and post-treatment, pre- and post-waiting, and at follow-up, and a sleep diary. As night shift workers alternate between sleeping during the day after their night shifts and transitioning to nighttime sleep on days off, insomnia severity and sleep variables were analysed for daytime and nighttime sleep. The BT-SWD involved sleep restriction therapy, stimulus control and fixed sleep periods in the dark. Statistical analyses were performed under intent-to-treat and per-protocol approaches. Repeated-measures two-way ANCOVA analysis, controlling for age, sex and pre-treatment daytime total sleep time, was performed with Bonferroni corrections, and between-group effect sizes computed. Fourteen participants dropped out after randomisation. Under the intent-to-treat analysis, BT-SWD participants had a significant greater decrease in daytime insomnia severity and an increase in daytime total sleep time at post-treatment than the control group, with large between-group effect sizes (-1.25 and 0.89). These corresponding results were also significant with large effect sizes under the per-protocol analysis. Sleepiness, anxiety and depression levels improved at post-treatment and maintained at follow-up when the BT-SWD treated controls were added to the BT-SWD group. The behavioural therapy for shift work disorder can be used to improve the sleep and mental health of healthcare night workers.

Whole-body procedural learning benefits from targeted memory reactivation in REM sleep and task-related dreaming.

Sleep facilitates memory consolidation through offline reactivations of memory traces. Dreaming may play a role in memory improvement and may reflect these memory reactivations. To experimentally address this question, we used targeted memory reactivation (TMR), i.e., application, during sleep, of a stimulus that was previously associated with learning, to assess whether it influences task-related dream imagery (or task-dream reactivations). Specifically, we asked if TMR or task-dream reactivations in either slow-wave (SWS) or rapid eye movement (REM) sleep benefit whole-body procedural learning. Healthy participants completed a virtual reality (VR) flying task prior to and following a morning nap or rest period during which task-associated tones were readministered in either SWS, REM sleep, wake or not at all. Findings indicate that learning benefits most from TMR when applied in REM sleep compared to a Control-sleep group. REM dreams that reactivated kinesthetic elements of the VR task (e.g., flying, accelerating) were also associated with higher improvement on the task than were dreams that reactivated visual elements (e.g., landscapes) or that had no reactivations. TMR did not itself influence dream content but its effects on performance were greater when coexisting with task-dream reactivations in REM sleep. Findings may help explain the mechanistic relationships between dream and memory reactivations and may contribute to the development of sleep-based methods to optimize complex skill learning.

Flying dreams stimulated by an immersive virtual reality task.

Despite a high prevalence and broad interest in flying dreams, these exceptional experiences remain infrequent. Our study aimed to (1) induce flying dreams using a custom-built virtual reality (VR) flying task, (2) examine their phenomenological correlates and (3) investigate their relations to participant state and trait factors. 137 participants underwent VR-flying followed by a morning nap. They also completed home dream journals for 5 days before and 10 days after the VR exposure. VR-flying successfully increased the reporting of flying dreams during the laboratory nap and on the following morning compared to both baseline frequencies and a control cohort. Flying dreams were also changed qualitatively, exhibiting higher levels of Lucid-control and emotional intensity, after VR exposure. Factors such as prior dream-flying experiences and level of VR sensory immersion modulated flying dream induction. Findings are consistent with a new vection-based explanation of dream-flying and may facilitate development of dream flight-induction technologies.

Attempted induction of signalled lucid dreaming by transcranial alternating current stimulation.

Neurophysiological correlates of self-awareness during sleep ('lucid dreaming') remain unclear despite their importance for clarifying the neural underpinnings of consciousness. Transcranial direct (tDC) and alternating (tAC) current stimulation during sleep have been shown to increase dream self-awareness, but these studies' methodological weaknesses prompted us to undertake additional study. tAC stimulation was associated with signal-verified and self-rated lucid dreams-but so was the sham procedure. Situational factors may be crucial to inducing self-awareness during sleep.

Elevated perseveration errors on a verbal fluency task in frequent nightmare recallers: a replication.

A recent study reported that individuals recalling frequent idiopathic nightmares (NM) produced more perseveration errors on a verbal fluency task than did control participants (CTL), while not differing in overall verbal fluency. Elevated scores on perseveration errors, an index of executive dysfunction, suggest a cognitive inhibitory control deficit in NM participants. The present study sought to replicate these results using a French-speaking cohort and French language verbal fluency tasks. A phonetic verbal fluency task using three stimulus letters (P, R, V) and a semantic verbal fluency task using two stimulus categories (female and male French first names) were administered to 23 participants with frequent recall of NM (≥2 NM per week, mean age = 24.4 ± 4.0 years), and to 16 CTL participants with few recalled NM (≤ 1 NM per month, mean age = 24.5 ± 3.8 years). All participants were French-speaking since birth and self-declared to be in good mental and physical health apart from their NM. As expected, groups did not differ in overall verbal fluency, i.e. total number of correct words produced in response to stimulus letters or categories (P = 0.97). Furthermore, groups exhibited a difference in fluency perseveration errors, with the NM group having higher perseveration than the CTL group (P = 0.03, Cohen's d = 0.745). This replication suggests that frequent NM recallers have executive inhibitory dysfunction during a cognitive association task and supports a neurocognitive model which posits fronto-limbic impairment as a neural correlate of disturbed dreaming.

Infrequent dream recall associated with low performance but high overnight improvement on mirror-tracing.

Although sleep facilitates learning and memory, the roles of dreaming and habitual levels of recalling dreams remain unknown. This study examined if performance and overnight improvement on a rapid eye movement sleep-sensitive visuomotor task is associated differentially with habitually high or low dream recall frequency. As a relation between dream production and visuospatial skills has been demonstrated previously, one possibility is that frequency of dream recall will be linked to performance on visuomotor tasks such as the Mirror Tracing Task. We expected that habitually low dream recallers would perform more poorly on the Mirror Tracing Task than would high recallers and would show less task improvement following a night of sleep. Fifteen low and 20 high dream recallers slept one night each in the laboratory and performed the Mirror Tracing Task before and after sleep. Low recallers had overall worse baseline performance but a greater evening-to-morning improvement than did high recallers. Greater improvements in completion time in low recallers were associated with Stage 2 rather than rapid eye movement sleep. Findings support the separate notions that dreaming is related to visuomotor processes and that different levels of visuomotor skill engage different sleep- and dream-related consolidation mechanisms.

Local Neuronal Synchronization in Frequent Nightmare Recallers and Healthy Controls: A Resting-State Functional Magnetic Resonance Imaging Study.

Nightmares are highly dysphoric dreams that are well-remembered upon awakening. Frequent nightmares have been associated with psychopathology and emotional dysregulation, yet their neural mechanisms remain largely unknown. Our neurocognitive model posits that nightmares reflect dysfunction in a limbic-prefrontal circuit comprising medial prefrontal and anterior cingulate cortices, hippocampus, and amygdala. However, there is a paucity of studies that used brain imaging to directly test the neural correlates of nightmares. One such study compared the regional homogeneity (ReHo) of resting-state functional magnetic resonance imaging blood-oxygen level-dependent signals between frequent nightmare recallers and controls. The main results were greater regional homogeneity in the left anterior cingulate cortex and right inferior parietal lobule for the nightmare recallers than for the controls. In the present study, we aimed to document the ReHo correlates of frequent nightmares using several nightmare severity measures. We acquired resting-state functional magnetic resonance imaging data from 18 frequent nightmare recallers aged 18-35 (3 males and 15 females) and 18 age- and sex-matched controls, as well as retrospective and prospective disturbed dreaming frequency estimates and scores on the Nightmare Distress Questionnaire. While there were inconsistent results for our different analyses (group comparisons, correlational analyses for frequency estimates/Nightmare Distress scores), our results suggest that nightmares are associated with altered ReHo in frontal (medial prefrontal and inferior frontal), parietal, temporal and occipital regions, as well as some subcortical regions (thalamus). We also found a positive correlation between retrospective disturbed dreaming frequency estimates and ReHo values in the hippocampus. These findings are mostly in line with a recent SPECT study from our laboratory. Our results point to the possibility that a variety of regions, including but not limited to the limbic-prefrontal circuit of our neurocognitive model, contribute to nightmare formation.

Changes in cardiac variability after REM sleep deprivation in recurrent nightmares.

STUDY OBJECTIVES: To assess whether dysfunctional autonomic regulation during REM sleep as indexed by heart rate variability (HRV) is a pathophysiological factor in frequent nightmares (NMs). DESIGN: Monitoring with polysomnography (PSG) and electrocardiography (ECG) for 3 consecutive nights: Night 1 (N1), adaptation night; N2, administration of partial REM sleep deprivation; N3, recovery night. Differences between NM and control (CTL) groups assessed for ECG measures drawn from wakefulness, REM sleep, and Stage 2 sleep on both N1 and N3. SETTING: Hospital-based sleep laboratory. PARTICIPANTS: Sixteen subjects with frequent NMs (> or = 1 NM/week; mean age = 26.1 +/- 8.7 years) but no other medical or psychiatric disorders and 11 healthy comparison subjects ( < 1 NM/month; mean age = 27.1+/- 5.6 years). RESULTS: NM and CTL groups differed on 2 REM sleep measures only on N1; the NM group had longer REM latencies and REM/NREM cycle durations than did the CTL group. No differences were found on time domain and absolute frequency domain ECG measures for either N1 or N3. However, altered HRV for the NM group was suggested by significantly higher LFnu, lower HFnu, and higher LF/HF ratio than for the CTL group. CONCLUSIONS: Results are consistent with a higher than normal sympathetic drive among NM subjects which is unmasked by high REM sleep propensity. Results also support a growing literature linking anxiety disorders of several types (panic disorder, posttraumatic stress disorder (PTSD), generalized anxiety disorder) to altered HR variability.

Early childhood adversity associations with nightmare severity and sleep spindles.

OBJECTIVE: Childhood adversity figures prominently in the clinical histories of children and adolescents suffering from a panoply of physical, mental or sleep disorders, including posttraumatic stress disorder. But the nature and prevalence of early adversity in the case of idiopathic nightmare-prone individuals have received little study. We characterize the types and frequencies of self-reported childhood adversity for nightmare-prone individuals using the developmentally sensitive Traumatic Antecedents Questionnaire (TAQ) and assess relationships between separation adversity and sleep spindles. METHOD: The TAQ was administered to 73 non-treatment-seeking volunteers with frequent idiopathic nightmares and 67 healthy controls. Nightmare severity, anxiety, depression, alexithymia and past and present sleep disorders were also assessed. Sleep was recorded with polysomnography (PSG) for 90 participants and sleep spindles were assessed for 63. RESULTS: Nightmare-prone participants scored higher on most TAQ measures, including adversity at 0-6 years of age. TAQ-derived scales assessing traumatic and nontraumatic forms of adversity were both elevated for nightmare-prone participants; for 0-6 year estimates, nontraumatic adversity was associated with nightmares independent of trauma adversity. Group differences were only partially mediated by current psychopathology symptoms and were largely independent of nightmare frequency but not of nightmare distress. Adversity/nightmare relationships were graded differentially for the two study groups. Separation adversity at 0-6 years of age correlated with current sleep spindle anomalies-in particular, lower slow spindle density-an anomaly known to index both psychopathology and early nightmare-onset. CONCLUSIONS: Self-reported adversity occurring as young as 0-6 years of age is associated with nightmare severity and sleep spindle anomalies. Adversity-linked nightmares may reflect pathophysiological mechanisms common also to the nightmares of pre-clinical and full-blown post-traumatic stress disorder.

Different Patterns of Sleep-Dependent Procedural Memory Consolidation in Vipassana Meditation Practitioners and Non-meditating Controls.

AIM: Rapid eye movement (REM) sleep, non-rapid eye movement (NREM) sleep, and sleep spindles are all implicated in the consolidation of procedural memories. Relative contributions of sleep stages and sleep spindles were previously shown to depend on individual differences in task processing. However, no studies to our knowledge have focused on individual differences in experience with Vipassana meditation as related to sleep. Vipassana meditation is a form of mental training that enhances proprioceptive and somatic awareness and alters attentional style. The goal of this study was to examine a potential role for Vipassana meditation experience in sleep-dependent procedural memory consolidation. METHODS: Groups of Vipassana meditation practitioners (N = 22) and matched meditation-naïve controls (N = 20) slept for a daytime nap in the laboratory. Before and after the nap they completed a procedural task on the Wii Fit balance platform. RESULTS: Meditators performed slightly better on the task before the nap, but the two groups improved similarly after sleep. The groups showed different patterns of sleep-dependent procedural memory consolidation: in meditators, task learning was positively correlated with density of slow occipital spindles, while in controls task improvement was positively associated with time in REM sleep. Sleep efficiency and sleep architecture did not differ between groups. Meditation practitioners, however, had a lower density of occipital slow sleep spindles than controls. CONCLUSION: Results suggest that neuroplastic changes associated with meditation practice may alter overall sleep microarchitecture and reorganize sleep-dependent patterns of memory consolidation. The lower density of occipital spindles in meditators may mean that meditation practice compensates for some of the memory functions of sleep.

Nightmare Severity Is Inversely Related to Frontal Brain Activity During Waking State Picture Viewing.

STUDY OBJECTIVES: Growing evidence suggests that nightmares have considerable adverse effects on waking behavior, possibly by increasing post-sleep negative emotions. Dysphoric reactions to nightmares are one component of nightmare severity for which the neural correlates are unknown. Here, we investigate possible neural correlates of nightmare severity in a sample of individuals who frequently recall nightmares. METHODS: Our principal measure of nightmare severity is nightmare distress as indexed by the Nightmare Distress Questionnaire (NDQ), and secondary measures are retrospective and prospective estimates of frequency of recalling dysphoric dreams (DD). We used high-resolution technetium 99m ethyl cysteinate dimer single photon emission computed tomography to assess regional cerebral blood flow (rCBF) while 18 individuals who were frequent nightmare recallers viewed negative and neutral pictures from the International Affective Picture System. We correlated rCBF with NDQ scores and DD recall frequency estimates. RESULTS: Negative correlations were observed between NDQ scores and rCBF during negative picture viewing in bilateral insula and anterior cingulate, right medial frontal gyrus, bilateral superior temporal gyrus, right inferior frontal and precentral gyri, and bilateral putamen. Retrospective DD recall correlated with rCBF activity primarily in regions overlapping those related to NDQ scores. Prospective DD recall was only weakly related to rCBF. Results for the neutral condition overlapped partially with those for the negative condition; in particular, NDQ and retrospective DD recall were related to rCBF in medial prefrontal and anterior cingulate gyri. CONCLUSIONS: Results point to a possible overlap in brain mechanisms involved in nightmare dysphoria (during sleep) and distress (during wakefulness) among individuals who frequently recall nightmares. They provide partial support for a neurocognitive model of nightmares. COMMENTARY: A commentary on this article appears in this issue on page 179.

Sleep spindles are altered in early- but not late-onset nightmare recallers.

Nightmares are a common sleep disorder, defined as highly disturbing mentation which usually awakens the individual from rapid eye movement (REM) sleep. While nightmares are mainly a REM sleep phenomenon, Picard-Deland et al., (2017) recently showed an association between nightmare recall and sleep spindles, which are a non-rapid eye movement (NREM) oscillatory feature. Their results pointed to fewer slow spindles and a higher oscillatory frequency for fast spindles among frequent nightmare recallers compared with controls. To test the suggestion that nightmares stem from changes to emotional neural circuits arising in early childhood (Nielsen, 2017), including early changes in sleep spindles (Scholle et al., 2007), we investigated if the spindle features of early-onset nightmare recallers (ie, recalling nightmares since childhood) (N = 22), differed from those of late-onset nightmare recallers (ie, since adolescence or adulthood) (N = 11), or from those of controls (N = 23). A retrospective analysis of the sleep spindles of 56 participants who had undergone a polysomnographically-recorded morning nap revealed that Early starters uniquely exhibited lower slow spindle densities in five of six derivations (all p < 0.045) and higher fast spindle frequencies in all six derivations (all p < 0.015). These results add precision to previously reported findings for Nightmare recallers: spindle differences are shown to hold only for Early starters. The lifelong occurrence of nightmares may be closely tied to disruptions in the normal development of spindle generation processes occurring early in development.

Sleep spindle and psychopathology characteristics of frequent nightmare recallers.

Idiopathic nightmares are a common disturbance of rapid eye movement sleep (REM) sleep, but studies of comorbid pathologies and sleep architecture suggest that non-REM (NREM) sleep is also affected. Sleep spindles are a NREM sleep characteristic associated with both pathophysiology and sleep-dependent memory consolidation, yet they have not been evaluated in frequent nightmare recallers. The morning naps of 38 participants with frequent idiopathic nightmares (mean age: 23.7 ± 3.78 years) and 25 age- and sex-matched controls (23.9 ± 3.65 years) were recorded and their sleep evaluated. A custom spindle detector assessed NREM sleep stage 2 (N2) sleep spindles on six electroencephalogram (EEG) derivations (F3, F4, C3, C4, O1, and O2) for density (number spindles/N2 time), mean frequency, and amplitude. Total spindles (10-16 Hertz (Hz) range), slow spindles (10-12.79 Hz), and fast spindles (12.8-16 Hz) were all assessed separately. Compared with the Control group, the Nightmare group had longer N2 sleep latency and a marginally greater %N2 sleep. The Nightmare group also had a lower than normal density of slow spindles in most EEG derivations, a higher density of fast spindles in frontal derivations, and an elevated fast spindle oscillatory frequency-"faster fast" spindles-mainly in central derivations. These differences withstood controls for pre-existing group differences in depression. Correlational analyses demonstrated a further pattern of group differences by which higher pathology scores were associated with higher slow spindle densities and slower spindle frequencies for the Nightmare but not the Control group. A similar pattern was observed for some dream content measures, ie, the Nightmare group showed positive correlations of slow spindle density with dreamed fear and word count and negative correlations with dreamed positive emotion. Conversely, the Control group showed opposite trends. Results thus demonstrate abnormalities in the composition of N2 sleep-and especially in N2 spindles-among frequent nightmare recallers and link these abnormalities to both trait (psychopathology) and state (dream content) factors. Spindle findings for psychopathology resemble, but are not identical with, previous findings for patients with major depression, social anxiety, and schizophrenia and are thus consistent with an explanation implicating spindles as trait markers of psychopathology. Correlational analyses go beyond a trait explanation to suggest several possible state-based explanations involving memory consolidation mechanisms, specifically, the possibility that spindles index either emotional or verbal task-based processes.

Dream-associated behaviors affecting pregnant and postpartum women.

STUDY OBJECTIVES: Evaluate the prevalence and phenomenology of dream-associated behaviors affecting pregnant and postpartum mothers. Episodes consist of anxious dreams and nightmares about the new infant that are accompanied by complex behaviors (motor activity, speaking, expressing emotion). DESIGN: Three-group design (postpartum, pregnant, null gravida), self-report, and repeated measures. SETTING: Pregnancy and postpartum groups: completion of questionnaires in hospital room within 48 hours of giving birth and home telephone interviews; null gravida group: completion of questionnaires and interview in person or by telephone. PARTICIPANTS: Two hundred seventy-three women in 3 groups: postpartum: n = 202 (mean age = 29.7 +/- 4.94 years; 95 primiparas, 107 multiparas); pregnant: n = 50 (mean age = 31.1 +/- 5.44 years); null gravida: n = 21 (mean age = 28.5 +/- 6.34 years). INTERVENTIONS: Subjects completed questionnaires about pregnancy and birth factors, personality, and sleep and participated in interviews concerning the prevalence of recent infant dreams and nightmares, associated behaviors, anxiety, depression, and other psychopathologic factors. MEASUREMENTS AND RESULTS: Most women in all groups recalled dreams (88%-91%). Postpartum and pregnant women recalled infant dreams and nightmares with equal prevalence, but more postpartum women reported they contained anxiety (75%) and the infant in peril (73%) than did pregnant women (59%, P < 0.05 and 42%, P < 0.0001). More postpartum (63%) than pregnant (40%) women reported dream-associated behaviors (P < 0.01), but neither group differed from null gravida women (56%). This was due to different distributions over groups of the behavior subtypes. Motor activity was present in twice as many postpartum (57%) as pregnant (24%) or null gravida (25%) women (all P < 0.0001). Expressing emotion was more prevalent among null gravida (56%) than postpartum women (27%) (P < 0.05) but was not different from pregnant women (37%). Speaking was equally prevalent among the 3 groups (12%-19%). Behaviors were associated with nightmares, dream anxiety and, among postpartum women, post-awakening anxiety (41%), confusion (51%), and a need to check on the infant (60%). Primiparas and multiparas differed in dream and nightmare recall but not in prevalence of dream-associated behaviors. CONCLUSION: The prevalent occurrence of pregnancy and postpartum infant dreams and associated behaviors may reflect the pervasive emotional influence of maternal concerns or changes instigated by severe sleep disruption, rapid eye movement sleep deprivation, and altered hormone levels.

REM Sleep Theta Changes in Frequent Nightmare Recallers.

Study Objectives: To replicate and expand upon past research by evaluating sleep and wake electroencephalographic spectral activity in samples of frequent nightmare (NM) recallers and healthy controls. Methods: Computation of spectral activity for sleep (non-REM and REM) and wake electroencephalogram recordings from 18 frequent NM recallers and 15 control participants. Results: There was higher "slow-theta" (2-5 Hz) for NM recallers than for controls during wake, non-REM sleep and REM sleep. Differences were clearest for frontal and central derivations and for REM sleep cycles 2-4. There was also higher beta activity during NREM sleep for NM recallers. Findings partially replicate past research by demonstrating higher relative "slow-theta" (3-4Hz) for NM recallers than for controls. Conclusions: Findings are consistent with a neurocognitive model of nightmares that stipulates cross-state anomalies in emotion processing in NM-prone individuals.

REM sleep characteristics of nightmare sufferers before and after REM sleep deprivation.

OBJECTIVES: To examine whether disrupted regulation of REM sleep propensity is implicated in nightmare (NM) pathophysiology. BACKGROUND: Heightened REM propensity induced by REM sleep deprivation is belied by increases in REM %, REM density and the dream-like quality of dream mentation during post-deprivation recovery sleep. Compromised regulation of REM sleep propensity may be a contributing factor in the pathophysiology of frequent NMs. METHODS: A preliminary study of 14 subjects with frequent NMs (> or = 1 NM/week; 27.6+/-9.9 years) and 11 healthy control subjects (<1 NM/month; 24.3+/-5.3 years) was undertaken. Subjects completed home sleep/dream logs and underwent three nights of polysomnographic recording with REM sleep deprivation on night 2. Group differences were assessed for a battery of REM sleep and dream measures on nights 1 and 3. RESULTS: Several measures, including #skipped early-night REM periods, REM latency, REM/NREM cycle length, early/late REM density, REM rebound, late-night REM% and dream vividness, suggested that REM sleep propensity was abnormally low for the frequent NM group throughout the 3-day study. CONCLUSIONS: Findings raise the possibility that REM anomalies recorded from NM sufferers sleeping in the laboratory environment reflect a disruption of one or more endogenous regulators of REM sleep propensity.

Reduced Alpha power associated with the recall of mentation from Stage 2 and Stage REM sleep.

Relationships between Alpha (8-12 Hz) activity and cognitive processes during wakefulness raise the possibility of similar relationships between Alpha and cognitive activity during sleep. We hypothesized that Alpha power decreases during both Stage 2 and REM sleep would index the presence of sleep mentation in these stages. Absolute power for six classical EEG bands and three Alpha subbands was calculated for Stage 2 and REM sleep awakenings both with and without mentation recall. In both stages, recall was associated with lower Alpha power, especially with middle Alpha power (9.5-11.5 Hz). Unexpectedly, a similar effect for Delta power (0.5-4.0 Hz) was also observed. The Alpha effect may reflect cognitive elaboration active in the minutes preceding awakening; however, attention and memory processes cannot be excluded. The Delta effect is consistent with prior observations of regular linkages between Alpha and Delta power during sleep.