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Memories of waking-life events are incorporated into dreams, but their incorporation is not uniform across a night of sleep. This study aimed to elucidate ways in which such memory sources vary by sleep stage and time of night. Twenty healthy participants (11 F; 24.1 ± 5.7 years) spent a night in the laboratory and were awakened for dream collection approximately 12 times spread across early, middle, and late periods of sleep, while covering all stages of sleep (N1, N2, N3, REM). In the morning, participants identified and dated associated memories of waking-life events for each dream report, when possible. The incorporation of recent memory sources in dreams was more frequent in N1 and REM than in other sleep stages. The incorporation of distant memories from over a week ago, semantic memories not traceable to a single event, and anticipated future events remained stable throughout sleep. In contrast, the relative proportions of recent versus distant memory sources changed across the night, independently of sleep stage, with late-night dreams in all stages having relatively less recent and more remote memory sources than dreams earlier in the night. Qualitatively, dreams tended to repeat similar themes across the night and in different sleep stages. The present findings clarify the temporal course of memory incorporations in dreams, highlighting a specific connection between time of night and the temporal remoteness of memories. We discuss how dream content may, at least in part, reflect the mechanisms of sleep-dependent memory consolidation.

Study Objectives Early research suggests that the vestibular system is implicated in lucid dreaming, e.g. frequent lucid dreamers outperform others on static balance tasks. Furthermore, gravity-themed dreams, such as flying dreams, frequently accompany lucid dreaming. Nonetheless, studies are scarce. Methods We attempted to: (1) replicate previous findings using more sensitive static balance measures and (2) extend these findings by examining relationships with dreamed gravity imagery more generally. 131 participants (80 F; Mage=24.1 ± 4.1 yrs) estimated lucid dreaming frequency then completed a 5-day home log with ratings for dream lucidity awareness, control, and gravity sensations (flying, falling). They then performed balance tasks on a sensitive force plate, i.e. standing on one or both feet, with eyes open or closed. Center of pressure (CoP) Displacement and CoP Velocity on each trial measured postural stability. Results Findings partially support the claim of a vestibular contribution to lucid dreaming. Frequent lucid dreamers displayed better balance (lower CoP Velocity) than did other participants on some trials and lucid dreaming frequency was globally correlated with better balance (lower CoP Velocity). Lower CoP Velocity was related to flying sensations in men’s dreams and with more dream control in women’s dreams. However, body height—possibly due to its relationship to sex—and levels of sleepiness confound some of these effects. Conclusion While findings only provide a partial replication of previous work, they nonetheless support an emerging view that the vestibular system underlies basic attributes of bodily self-consciousness, such as feelings of self-agency and self-location, whether such consciousness occurs during wakefulness or dreaming.

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.

Although new learning is known to reappear in later dream scenarios, the timing of such reappearances remains unclear. Sometimes, references to new learning occur relatively quickly, 1 day post-learning (day-residue effect); at other times there may be a substantive delay, 5-7 days, before such references appear (dream-lag effect). We studied temporal delays in dream reactivation following the learning of a virtual reality (VR) flying task using 10-day home sleep/dream logs, and how these might be influenced by targeted memory reactivation (TMR). Participants were exposed twice to a VR task in the sleep laboratory; once before and once after a 2-hr opportunity to nap (n = 65) or to read (n = 32). Auditory cues associated with the VR task were replayed in either wake, rapid eye movement (REM) sleep, slow-wave sleep (SWS) or were not replayed. Although we previously showed that TMR cueing did not have an immediate effect on dream content, in the present study we extend these results by showing that TMR in sleep has instead a delayed effect on task-dream reactivations: participants dreamed more about the task 1-2 days later when TMR was applied in REM sleep and 5-6 days later when it was applied in SWS sleep, compared to participants with no cueing. Findings may help explain the temporal relationships between dream and memory reactivations and clarify the occurrence of day-residue and dream-lag phenomena.

The loss of vision, particularly when it occurs early in life, is associated with compensatory cortical plasticity not only in the visual cortical areas, but throughout the entire brain. The absence of visual input to the retina can also induce changes in entrainment of the circadian rhythm, as light is the primary zeitgeber of the master biological clock found in the suprachiasmatic nucleus of the hypothalamus. In addition, a greater number of sleep disturbances is often reported in blind individuals. Here, we examined various electroencephalographic microstructural components of sleep, both during rapid-eye-movement (REM) sleep and non-REM (NREM) sleep, between blind individuals, including both of early and late onset, and normal-sighted controls. During wakefulness, occipital alpha oscillations were lower, or absent in blind individuals. During sleep, differences were observed across electrode derivations between the early and late blind samples, which may reflect altered cortical networking in early blindness. Despite these differences in power spectra density, the electroencephalography microstructure of sleep, including sleep spindles, slow wave activity, and sawtooth waves, remained present in the absence of vision.

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.

Both rapid eye movement (REM) sleep dreaming and non-rapid eye movement (NREM) sleep spindles have been linked to processes of memory consolidation. However, relationships between the two phenomena have yet to be explored. In a heterogeneous sample of 53 healthy subjects who had participated in a memory consolidation protocol and who varied in their self-reported recall of dreams and nightmares, we assessed overnight polysomnography, N2 sleep spindle density, REM dream word count, and retrospective estimates of how often they recall dreams, bad dreams (dysphoric dreams, no awakening), and nightmares (dysphoric dreams, with awakenings). Fast spindle density positively correlated with all measures of dream recall but was most robustly associated with bad dream recall and REM dream word count. Correlations with bad dream recall were particularly strong for spindles occurring in sleep cycles 2 and 3 and correlations with word count for cycles 1, 4, and 5. While slow spindle density showed opposite correlation...

Introduction Flying is a prevalent but infrequent experience in dreams. Despite a broad interest in such unique dream experiences, there is still no experimental procedure for reliably inducing them. Our study aimed 1) to induce flying dreams in the laboratory using virtual reality (VR), 2) to examine phenomenological correlates of flying dreams, such as lucidity and emotions and 3) to investigate the dynamics of dreamed gravity imagery in relation to participant state and trait factors. Methods A total of 137 healthy participants (24.01±4.03 y.o.; 85 F; 52 M) took part in a custom-built immersive VR task in which they learn how to ‘fly’ as precisely and quickly as possible, engaging vestibular, motor and visuo-spatial systems. Dreams were collected a) from home dream journals for 5 days before and 10 days after the laboratory VR task and b) after a 90-min morning nap in laboratory. Dream reports were scored by 2 independent judges for flying and other gravity-related imagery. Linear mixed models statistics were used to compare dreams from this cohort with a separate control cohort (N=52) that followed a similar protocol in the same lab but did not undertake a virtual flying task. Results The VR task successfully increased the likelihood of experiencing flying in dreams from both the laboratory nap (7.1%) and the following night (10.6%) compared to baseline (1.3%) and the control cohort on those days (Lab: 2.4%; following night: 0%). In contrast, the occurrence of other gravity imagery showed no differences. Flying dreams were altered qualitatively, exhibiting higher levels of lucid-control and emotional intensity after VR exposure. Moreover, various factors such as sex, prior dream experiences and sensory immersion in VR differentially modulated flying dream induction. Conclusion Our findings provide both quantitative and qualitative insights into flying dreams that may facilitate understanding of these typical dream experiences and future developments in dream flight-induction technologies. Support Natural Sciences and Engineering Research Council of Canada

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-naive 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.

There is ongoing controversy regarding the role of rapid eye movements (EMs) during rapid eye movement (REM) sleep. One prevailing hypothesis is that EMs during REM sleep are indicative of the presence of visual imagery in dreams. We tested the validity of this hypothesis by measuring EMs in blind subjects and correlating these with visual dream content. Eleven blind subjects, of whom five were congenitally blind (CB) and six late blind (LB), and 11 matched sighted control (SC) subjects participated in this study. All participants underwent full-night polysomnography (PSG) recordings that were staged manually following American Academy of Sleep Medicine (AASM) criteria. Nocturnal EMs were detected automatically using a validated EM detector, and EM activity was represented as "EM coverage" computed as percentage of time with EM in each sleep stage. Frequency of sensory dream elements was measured in dream recall questionnaires over a 30-day period. Both blind groups showed less EM coverage during wakefulness, N1, N2 and REM sleep than did controls. CB and LB subjects did not differ in EM activity. Validation of the detector applied to blind subjects revealed an overall accuracy of 95.6 ± 3.6%. Analysis of dream reports revealed that LB subjects reported significantly more visual dream elements than did CB. Although no specific mechanisms can be revealed in the current study, the quasi absence of nocturnal EMs in LB subjects despite preserved visual dream content does not support the visual scanning of dreams hypothesis. Specifically, results suggest a dissociation between EMs and visual dream content in blind individuals.

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.

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.

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. CITATION: Marquis LP, Julien SH, Baril AA, Blanchette-Carrière C, Paquette T, Carr M, Soucy JP, Montplaisir J, Nielsen T. Nightmare severity is inversely related to frontal brain activity during waking state picture viewing. J Clin Sleep Med. 2019;15(2):253–264.

The fleeting dream images of sleep onset afford a rare glimpse at how experience is transformed from the perceptually grounded consciousness of wakefulness to the hallucinatory simulations of dreaming. These images, or microdreams, are briefer, simpler, and more accessible to phenomenological scrutiny than are the long REM dreams traditionally recorded in the sleep lab. This chapter shows that a focus on microdream phenomenology has thus far contributed to (1) developing a classification system for dreaming’s core phenomenology (Windt`s oneiragogic spectrum), (2) establishing a structure for assessing dreaming’s multiple memory inputs (multi-temporal memory sources), (3) furthering Silberer’s project for sleep onset imagery by uncovering two new types of imagery (autosensory imagery, exosensory imagery), and (4) providing a larger framework for explaining some microdreaming processes (multisensory integration approach). A continued focus on microdream neurophenomenology may help resolve outstanding questions about dreaming’s core features, neurophysiological correlates, and memory sources.

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.

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.

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.

Summary Manual processing of sleep recordings is extremely time-consuming. Efforts to automate this process have shown promising results, but automatic systems are generally evaluated on private databases, not allowing accurate cross-validation with other systems. In lacking a common benchmark, the relative performances of different systems are not compared easily and advances are compromised. To address this fundamental methodological impediment to sleep study, we propose an open-access database of polysomnographic biosignals. To build this database, whole-night recordings from 200 participants [97 males (aged 42.9 ± 19.8 years) and 103 females (aged 38.3 ± 18.9 years); age range: 18–76 years] were pooled from eight different research protocols performed in three different hospital-based sleep laboratories. All recordings feature a sampling frequency of 256 Hz and an electroencephalography (EEG) montage of 4–20 channels plus standard electro-oculography (EOG), electromyography (EMG), electrocardiography (ECG) and respiratory signals. Access to the database can be obtained through the Montreal Archive of Sleep Studies (MASS) website (http://www.ceams-carsm.ca/en/MASS), and requires only affiliation with a research institution and prior approval by the applicant's local ethical review board. Providing the research community with access to this free and open sleep database is expected to facilitate the development and cross-validation of sleep analysis automation systems. It is also expected that such a shared resource will be a catalyst for cross-centre collaborations on difficult topics such as improving inter-rater agreement on sleep stage scoring.

Background A convergence of studies has revealed sleep spindles to be associated with sleep-related cognitive processing and even with fundamental waking state capacities such as intelligence. However, some spindle characteristics, such as propagation direction and delay, may play a decisive role but are only infrequently investigated because of technical complexities. New method A new methodology for assessing sleep spindle propagation over the human scalp using noninvasive electroencephalography (EEG) is described. This approach is based on the alignment of time-frequency representations of spindle activity across recording channels. Results This first of a two-part series concentrates on framing theoretical considerations related to EEG spindle propagation and on detailing the methodology. A short example application is provided that illustrates the repeatability of results obtained with the new propagation measure in a sample of 32 night recordings. A more comprehensive experimental investigation is presented in part two of the series. Comparison with existing method(s) Compared to existing methods, this approach is particularly well adapted for studying the propagation of sleep spindles because it estimates time delays rather than phase synchrony and it computes propagation properties for every individual spindle with windows adjusted to the specific spindle duration. Conclusions The proposed methodology is effective in tracking the propagation of spindles across the scalp and may thus help in elucidating the temporal aspects of sleep spindle dynamics, as well as other transient EEG and MEG events. A software implementation (the Spyndle Python package) is provided as open source software.

Study Objectives: Idiopathic REM sleep behavior disorder (iRBD) is characterized by atypical REM sleep motor activity, vivid dreams and nightmares, and dream-enacting behaviors that can result in injuries to the patient and bed partner. It is also a known predictor of Parkinson disease (PD). Alexithymia has been associated with disturbances in sleep and dreaming (e.g., nightmares) and is a non-motor symptom of PD. We assessed alexithymia and disturbed dreaming in iRBD patients with the aim of determining if these two factors are elevated and interrelated among this population. Design: Questionnaire study of clinically diagnosed patients. Setting: Clinical sleep disorders center. Patients or participants: Thirty-two iRBD patients and 30 healthy age- and sex-matched control participants. Measurements and Results: Participants completed the 20-item Toronto Alexithymia Scale (TAS-20), the Dream Questionnaire, and the Beck Depression Inventory. iRBD patients obtained higher TAS-20 total scores (62.16 ± 13.90) than did controls (52.84 ± 7.62; F1,59 = 10.44, P < 0.01), even when controlling for depressive symptoms, and more frequently attained the suggested cutoff for alexithymia than did controls (P < 0.01). iRBD patients obtained higher scores on the Difficulty Identifying Feelings alexithymia subscale. For both iRBD and control groups, the Difficulty Indentifying Feelings subscale correlated positively with the Nightmare Distress scale of the Dream Questionnaire. Conclusions: Elevated alexithymia scores among idiopathic rapid eye movement sleep behavior disorder patients, and especially a difficulty in identifying feelings, parallels evidence of dysautonomia in this population. The higher incidence of distressing nightmares and the association of nightmares with alexithymia further extend similar findings for both clinical and non-clinical samples and suggest that an affect regulation disturbance may be common to the two sets of symptoms.

Nightly transitions into sleep are usually uneventful and transpire in the blink of an eye. But in the laboratory these transitions afford a unique view of how experience is transformed from the perceptually grounded consciousness of wakefulness to the hallucinatory simulations of dreaming. The present review considers imagery in the sleep-onset transition—“microdreams” in particular—as an alternative object of study to dreaming as traditionally studied in the sleep lab. A focus on microdream phenomenology has thus far proven fruitful in preliminary efforts to (i) develop a classification for dreaming’s core phenomenology (the “oneiragogic spectrum”), (ii) establish a structure for assessing dreaming’s multiple memory inputs (“multi-temporal memory sources”), (iii) further Silberer’s project for classifying sleep-onset images in relation to waking cognition by revealing two new imagery types (“autosensory imagery,” “exosensory imagery”), and (iv) embed a potential understanding of microdreaming processes in a larger explanatory framework (“multisensory integration approach”). Such efforts may help resolve outstanding questions about dream neurophysiology and dreaming’s role in memory consolidation during sleep but may also advance discovery in the neuroscience of consciousness more broadly.

Face recognition is a highly specialized capability that has implicit and explicit memory components. Studies show that learning tasks with facial components are dependent on rapid eye movement and non-rapid eye movement sleep features, including rapid eye movement sleep density and fast sleep spindles. This study aimed to investigate the relationship between sleep-dependent consolidation of memory for faces and partial rapid eye movement sleep deprivation, rapid eye movement density, and fast and slow non-rapid eye movement sleep spindles. Fourteen healthy participants spent 1 night each in the laboratory. Prior to bed they completed a virtual reality task in which they interacted with computer-generated characters. Half of the participants (REMD group) underwent a partial rapid eye movement sleep deprivation protocol and half (CTL group) had a normal amount of rapid eye movement sleep. Upon awakening, they completed a face recognition task that contained a mixture of previously encountered faces from the task and new faces. Rapid eye movement density and fast and slow sleep spindles were detected using in-house software. The REMD group performed worse than the CTL group on the face recognition task; however, rapid eye movement duration and rapid eye movement density were not related to task performance. Fast and slow sleep spindles showed differential relationships to task performance, with fast spindles being positively and slow spindles negatively correlated with face recognition. The results support the notion that rapid eye movement and non-rapid eye movement sleep characteristics play complementary roles in face memory consolidation. This study also raises the possibility that fast and slow spindles contribute in opposite ways to sleep-dependent memory consolidation.

Summary We examined the structure, duration and quality of sleep, including non-rapid eye movement sleep and rapid eye movement sleep, in 11 blind individuals without conscious light perception and 11 age- and sex-matched sighted controls. Because blindness is associated with a greater incidence of free-running circadian rhythms, we controlled for circadian phase by a measure of melatonin onset timing. When circadian rhythm was entrained and melatonin onset occurred at normal times, sleep structure did not differ between blind and sighted individuals. On the other hand, an abnormal timing of the circadian phase, including delayed, shifted and unclassifiable melatonin onsets, led to larger rapid eye movement sleep latencies and increased wake times. No differences were observed for stages of non-rapid eye movement sleep, either between congenital and late blind and sighted individuals, or across the different circadian phases. Moreover, abnormal circadian phases were more common in the blind (n = 5) than the sighted (n = 2) sample. Our findings suggest that the sleep structure of blind individuals depends on entrainment of circadian phase, rather than on the absence of vision.

Consciousness is often said to disappear in deep, dreamless sleep. We argue that this assumption is oversimplified. Unless dreamless sleep is defined as unconscious from the outset there are good empirical and theoretical reasons for saying that a range of different types of sleep experience, some of which are distinct from dreaming, can occur in all stages of sleep. We introduce a novel taxonomy for describing different kinds of dreamless sleep experiences and suggest research methods for their investigation. Future studies should focus on three areas: memory consolidation, sleep disorders, and sleep state (mis)perception. Our proposal suggests new directions for sleep and dream science, as well as for the neuroscience of consciousness, and can also inform the diagnosis and treatment of sleep disorders.

Sleep fragmentation in infancy can burden a family by disrupting the sleep of all its members. However, there has been no longitudinal prospective investigation of the determinants of infant sleep fragmentation. We undertook such an investigation. New mothers (N = 106) completed questionnaires and were administered structured telephone interviews at three, six and 12 weeks postpartum. Pre- and postnatal maternal adjustment and sleep-related parental practices were evaluated as potential predictors of infants’ sleep fragmentation. Risk factors for infants sleeping less than six consecutive hours per night at 12 weeks were found to be mother’s depressed mood (OR = 1.55, p < .01), breastfeeding (OR = 6.40, p < .01) and room sharing (OR = 2.91, p < .05). The mother’s depressed mood and breastfeeding were also related to poor sleep consolidation when the latter was assessed as a continuous outcome (p < .01). This study identifies factors to target in sleep-focused interventions in families where the child’s sl...

Increasing evidence supports the clinical view that alexithymia is associated with disturbed dreaming. However, a consistent, replicable pattern of relationships between alexithymia and different dreaming components has not yet been identified. Groups of sleep-disordered outpatients (N 580; 46.0 13.2 years) and nonclinical controls (N 145; 22.9 4.2 years) were administered the Toronto Alexithymia Scale (TAS-20) and a 14-item Dreaming Questionnaire. Sleep diagnoses were assessed from polysomnography and clinical histories following the American Academy of Sleep Medicine classification system. The Dreaming Questionnaire was reduced by principal-components analysis to a 3-factor solution that distinguishes nightmare distress, dream recall, and dream meaning items. Factor coefficients were correlated with TAS total score and TAS subscales while age was controlled as a covariate. TAS total score was found to correlate positively with nightmare distress and negatively with dream recall for both clinical and nonclinical groups and for both men and women considered separately. TAS total score also correlated negatively with dream meaning for nonclinical participants. TAS subscales were differentially correlated with the 3 dream factors: difficulty identifying feelings (DIF) with increased nightmare distress, difficulty describing feelings (DDF) with decreased dream recall and externally oriented thinking (EOT) with decreased dream meaning. With some exceptions, these patterns were obtained independently for clinical and nonclinical groups and for men and women within these groups. Findings suggest a consistent and replicable pattern of relationships between alexithymia and dreaming components that implicates processes regulating emotion during both wakefulness and dreaming, for example, affect distress, expressive anxiety, and openness to experience.

This consensus paper provides an overview of the state of the art in research on the aetiology and treatment of nightmare disorder and outlines further perspectives on these issues. It presents a definition of nightmares and nightmare disorder followed by epidemiological findings, and then explains existing models of nightmare aetiology in traumatized and non‐traumatized individuals. Chronic nightmares develop through the interaction of elevated hyperarousal and impaired fear extinction. This interplay is assumed to be facilitated by trait affect distress elicited by traumatic experiences, early childhood adversity and trait susceptibility, as well as by elevated thought suppression and potentially sleep‐disordered breathing. Accordingly, different treatment options for nightmares focus on their meaning, on the chronic repetition of the nightmare or on maladaptive beliefs. Clinically, knowledge of healthcare providers about nightmare disorder and the delivery of evidence‐based interventions in the healthcare system is discussed. Based on these findings, we highlight some future perspectives and potential further developments of nightmare treatments and research into nightmare aetiology.

SUMMARY The AMPHAC/AND network is a vital componentof the physiologic infrastructure of normaldreaming and likely influences the shaping ofemotional imagery during normal and DD. By itsendemic nature, dreaming is a naturally occurringself-regulatory process that may operate muchlike the emotional processing and habituation ordesensitization that occurs during exposuretherapy. 51,96 Thus, the nature and quality of REMsleep in particular likely interacts with these brainregions in the formation of dream imagery to facil-itate the reduction or even elimination of fear-based memories in an ongoing attempt atachieving emotional homeostasis and optimizesurvival function. REFERENCES 1. Freud S. The interpretation of dreams. New York:Basic Books; 1955.2. Gilboa A, Shalev AY, Laor L, et al. Functionalconnectivity of the prefrontal cortex and the amyg-dala in posttraumatic stress disorder. Biol Psychiatry2004;55:263–72.3. Jung CG. Dreams: the collected works of C.G. Jung.Princeton (NJ): Princeton University Press; 1974.4. Maquet P, Pe´ters J-M, Aerts J, et al. Functionalneuroanatomy of human rapid-eye-movementsleep and dreaming. J Cogn Neurosci 1996;383:163–6.5. McGaugh JL. The amygdala modulates the consol-idation of memories of emotionally arousing experi-ences. Annu Rev Neurosci 2004;27:1–28.6. Hobson JA, Pace-Schott E, Stickgold R. Dreamingand the brain: towards a cognitive neuroscienceof conscious states. Behav Brain Sci 2000;23:793–842.7. Kramer M. The selective mood regulatory function ofdreaming: an update and revision. In: Moffitt A,Kramer M, Hoffmann R, editors. The functions ofdreaming. Albany (NY): State University of NewYork; 1993. p. 139–96.8. Cartwright R. Dreaming as a mood regulationsystem. In: Kryger MH, Roth T, Dement WC,editors. Principles and practice of sleep medicine.4th edition. Philadelphia: Elsevier Saunders; 2005.p. 565–72.9. Cartwright RD. Affect and dream work from an infor-mation processing point of view. J Mind Behav 1986;7:411–27.10. Vogel GW. A review of REM sleep deprivation. ArchGen Psychiatry 1975;32:749–61.11. Cartwright RD, Kravitz HM, Eastman CI, et al.REM latency and the recovery from depression:getting over divorce. Am J Psychiatry 1991;148:1530–5.12. Brown RJ, Donderi DC. Dream content and self-re-ported well-being among recurrent dreamers, past-recurrent dreamers, and nonrecurrent dreamers.J Pers Soc Psychol 1986;50:612–23.13. Cartwright RD. The nature and function of repetitivedreams: a survey and speculation. Psychiatry 1979;42:131–7.14. Zadra A, Desjardins S, Marcotte E. Evolutionaryfunction of dreams: a test of the threat simulationtheory in recurrent dreams. Conscious Cogn 2006;15:450–63.15. Bremner JD, Vythilingam M, Vermetten E, et al.Neural correlates of declarative memory for emotion-ally valenced words in women with posttraumatic236

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.

STUDY OBJECTIVES: Determine the prevalence and gender distributions of behaviors enacted during dreaming ("dream-enacting [DE] behaviors") in a normal population; the independence of such behaviors from other parasomnias; and the influence of different question wordings, socially desirable responding and personality on prevalence. DESIGN: 3-group questionnaire study. SETTING: University classrooms PARTICIPANTS: Three undergraduate samples (Ns = 443, 201, 496; mean ages = 19.9 +/- 3.2 y; 20.1 +/- 3.4 y; 19.1 +/- 1.6 y). INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Subjects completed questionnaires about DE behaviors and Social Desirability. Study 1 employed a nonspecific question about the behaviors, Study 2 employed the same question with examples, and Study 3 employed 7 questions describing specific behavior subtypes (speaking, crying, smiling/laughing, fear, anger, movement, sexual arousal). Somnambulism, somniloquy, nightmares, dream recall, alexithymia, and absorption were also assessed. Factor analyses were conducted to determine relationships among DE behaviors and their independence from other parasomnias. Prevalence increased with increasing question specificity (35.9%, 76.7%, and 98.2% for the 3 samples). No gender difference obtained for the nonspecific question, but robust differences occurred for more specific questions. Females reported more speaking, crying, fear and smiling/laughing than did males; males reported more sexual arousal. When controlling other parasomnias and dream recall frequency, these differences persisted. Factor solutions revealed that DE behaviors were independent of other parasomnias and of dream recall frequency, except for an association between dream-talking and somniloquy. Sexual arousal was related only to age. Behaviors were independent of alexithymia but moderately related to absorption. CONCLUSIONS: Dream-enacting behaviors are prevalent in healthy subjects and sensitive to question wording but not social desirability. Subtypes are related, differ with gender and occur independently of other parasomnias. Language: en

Rapid eye movement (REM) sleep and dreaming may be implicated in cross-night adaptation to emotionally negative events. To evaluate the impact of REM sleep deprivation (REMD) and the presence of dream emotions on a possible emotional adaptation (EA) function, 35 healthy subjects randomly assigned to REMD (n = 17; mean age 26.4 +/- 4.3 years) and control (n = 18; mean age 23.7 +/- 4.4 years) groups underwent a partial REMD and control nights in the laboratory, respectively. In the evening preceding and morning following REMD, subjects rated neutral and negative pictures on scales of valence and arousal and EA scores were calculated. Subjects also rated dream emotions using the same scales and a 10-item emotions list. REMD was relatively successful in decreasing REM% on the experimental night, although a mean split procedure was applied to better differentiate subjects high and low in REM%. High and low groups differed - but in a direction contrary to expectations. Subjects high in REMD% showed greater adaptation to negative pictures on arousal ratings than did those low in REMD% (P < 0.05), even after statistically controlling sleep efficiency and awakening times. Subjects above the median on EA(valence) had less intense overall dream negativity (P < 0.005) and dream sadness (P < 0.004) than subjects below the median. A correlation between the emotional intensities of the morning dream and the morning picture ratings supports a possible emotional carry-over effect. REM sleep may enhance morning reactivity to negative emotional stimuli. Further, REM sleep and dreaming may be implicated in different dimensions of cross-night adaptation to negative emotions.

This study investigated the effectiveness of a psychotherapeutic treatment for nightmares that was adapted for 6- to 11-year-old children from imagery rehearsal therapy. Ten child-mother dyads took part in a 3-session, 8-week treatment protocol. Participation in the study (contact with clinician, keeping a prospective dream log) was associated with decreases unpleasant dreams frequency, nightmare distress, and manifest anxiety. Providing educational information about nightmares did contribute to this positive effect. Results also suggest that drawing modified versions of nightmares for 1 month was associated with further reductions in nightmare distress and anxiety, but with no changes in unpleasant dreams frequency. Follow-ups at 3 and 6 months posttreatment suggest that the intervention had maintained effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved).

Cheyne and Girard characterize felt presence (FP) during sleep paralysis attacks as a pre-hallucinatory expression of a threat-activated vigilance system. While their results may be consistent with this interpretation, they are nonetheless correlational and do not address a parsimonious alternative explanation. This alternative stipulates that FP is a purely spatial, hallucinatory form of a common cognitive phenomenon-social imagery-that is often, but not necessarily, linked with threat and fear and that may induce distress among susceptible individuals. The occurrence of both fearful and non-fearful FPs in a multiplicity of situations other than sleep paralysis attacks supports the notion that FPs are hallucinatory variants of social imagery and that they are not necessarily bound to threat-activated vigilance. Evidence linking FPs with anxiety disorders supports the notion that the distress they evoke may be mediated by a more general affective distress personality factor. To illustrate the predominantly spatial character of FP hallucinations, similarities between FP and phantom limbs are summarized and the possibility that these two phenomena are parallel expressions (self- vs. other-presence) of a mirror neuron system is considered.