Is there a relation among REM sleep dissociated phenomena, like lucid dreaming, sleep paralysis, out-of-body experiences, and false awakening?

Out-of-body experiences in relation to lucid dreaming and sleep paralysis: A theoretical review and conceptual model

Out-of-body experiences (OBEs) are characterized by the subjective experience of being located outside the physical body. Little is known about the neurophysiology of spontaneous OBEs, which are often reported by healthy individuals as occurring during states of reduced vigilance, particularly in proximity to or during sleep (sleep-related OBEs). In this paper, we review the current state of research on sleep-related OBEs and hypothesize that maintaining consciousness during transitions from wakefulness to REM sleep (sleep-onset REM periods) may facilitate sleep-related OBEs. Based on this hypothesis, we propose a new conceptual model that potentially describes the relationship between OBEs and sleep states. The model sheds light on the phenomenological differences between sleep-related OBEs and similar states of consciousness, such as lucid dreaming (the realization of being in a dream state) and sleep paralysis (feeling paralyzed while falling asleep or waking up), and explores the potential polysomnographic features underlying sleep-related OBEs. Additionally, we apply the predictive coding framework and suggest a connecting link between sleep-related OBEs and OBEs reported during wakefulness.

To be or not to be hallucinating: Implications of hypnagogic/hypnopompic experiences and lucid dreaming for brain disorders

The boundaries between waking and sleeping-when falling asleep (hypnagogic) or waking up (hypnopompic)-can be challenging for our ability to monitor and interpret reality. Without proper understanding, bizarre but relatively normal hypnagogic/hypnopompic experiences can be misinterpreted as psychotic hallucinations (occurring, by definition, in the fully awake state), potentially leading to stigma and misdiagnosis in clinical contexts and to misconception and bias in research contexts. This Perspective proposes that conceptual and practical understanding for differentiating hallucinations from hypnagogic/hypnopompic experiences may be offered by lucid dreaming, the state in which one is aware of dreaming while sleeping. I first introduce a possible systematization of the phenomenological range of hypnagogic/hypnopompic experiences that can occur in the transition from awake to REM dreaming (including hypnagogic perceptions, transition symptoms, sleep paralysis, false awakenings, and out-of-body experiences). I then outline how metacognitive strategies used by lucid dreamers to gain/confirm oneiric lucidity could be tested for better differentiating hypnagogic/hypnopompic experiences from hallucinations. The relevance of hypnagogic/hypnopompic experiences and lucid dreaming is analyzed for schizophrenia and narcolepsy, and discussed for neurodegenerative diseases, particularly Lewy-body disorders (i.e. Parkinson's disease, Parkinson's disease dementia, and dementia with Lewy bodies), offering testable hypotheses for empirical investigation. Finally, emotionally positive lucid dreams triggered or enhanced by training/induction strategies or by a pathological process may have intrinsic therapeutic value if properly recognized and guided. The overall intention is to raise awareness and foster further research about the possible diagnostic, prognostic, and therapeutic implications of hypnagogic/hypnopompic experiences and lucid dreaming for brain disorders.

Prevalence and Clinical Characteristics of Sleeping Paralysis: A Systematic Review and Meta-Analysis

Sleep paralysis (SP) is a mixed state of consciousness and sleep, combining features of rapid eye movement (REM) sleep with those of wakefulness. The exact cause of SP is unknown, and its prevalence varies among the studies. We aim to identify SP's global prevalence, the affected population's characteristics, and the SP's clinical picture. We searched three databases (PubMed, Scopus, and Web of Science (WoS)) using a unique search strategy to identify eligible studies. All observational studies identifying the prevalence or frequency of sleeping paralysis were included. No exclusions are made based on country, race, or questionnaire. The analysis was performed using the latest version of R software (R Core Team, Vienna, Austria). The analysis included 76 studies from 25 countries with 167,133 participants. The global prevalence of SP was 30% (95% CI (22%, 39%)). There were similar frequencies of isolated SP and SP (33%, 95% CI (26%, 42%), I2 = 97%, P <0.01; 31%, 95% CI (21%, 43%), I2 = 100%, P = 0, respectively). A subgroup analysis showed that the majority of those who experienced SP were psychiatric patients (35%, 95% CI (20%, 55%), I2 = 96%, P <0.01). The prevalence among non-psychiatric patients was among students (34%, 95% CI (23%, 47%), I2 = 100%, P = 0). Auditory and visual hallucinations were reported in 24.25% of patients. Around 4% had only visual hallucinations. Meta-regression showed no association between the frequency of SP and sex. Publication bias was detected among the included studies through visual inspection of funnel plot asymmetry. Our findings revealed that 30% of the population suffered from SP, especially psychiatric patients and students. The majority of SP cases lacked associated hallucinations, while a noteworthy proportion experienced combined visual and auditory hallucinations.

Detecting Lucid Dreams by Electroencephalography and Eyebrow Movements

Objective  When metacognition arises during rapid eye movement (REM) sleep, people experience lucid dreaming (LD). Studies on this phenomenon face different obstacles. For example, its standard verification protocol requires at least three types of sensors. We hypothesized that preagreed frontalis movements (PAFMs), as a sign of lucidity, could be seen on electroencephalography (EEG) during REM sleep. In this case, only one EEG sensor would be needed to verify LD. Method  Under laboratory observation, five volunteers were instructed to induce LD, during which they needed to use the standard verification protocol with pre-agreed eye movements (PAEMs) and then immediately raise their eyebrows three times as a PAFM. Results  All participants were able to send signals from a total of eight LDs using one or both methods. Preagreed frontalis movements and PAEMs were equally distinctive on most EEGs, but PAFM quality was strongly dependent on the accuracy of the method. Preagreed frontalis movements exhibited two types of EEG patterns and led to immediate awakening when LD was not stable. Discussion  Though the outcomes show that PAFMs can be used to verify LD, this method was less consistent and apparent than PAEMs. Furthermore, accurate instructions are needed before using PAFMs. When polysomnography is unavailable, PAFMs can be applied, as it requires only one EEG sensor to detect REM sleep and consciousness simultaneously.

Associations between sleep variables and ostensibly paranormal experiences and paranormal beliefs: A scoping review

Night-time is a period of great significance for many people who report paranormal experiences. However, there is limited understanding of the associations between sleep variables and seemingly paranormal experiences and/or beliefs. The aim of this review is to improve our understanding of these associations while unifying a currently fragmented literature-base into a structured, practical review. In this pre-registered scoping review, we searched for relevant studies in MEDLINE (PubMed), PsycINFO (EBSCO), Web of Science and EMBASE using terms related to sleep and ostensibly paranormal experiences and beliefs. Forty-four studies met all inclusion criteria. All were cross-sectional and most investigated sleep paralysis and/or lucid dreaming in relation to ostensibly paranormal experiences and paranormal beliefs. Overall, there were positive associations between many sleep variables (including sleep paralysis, lucid dreams, nightmares, and hypnagogic hallucinations) and ostensibly paranormal experiences and paranormal beliefs (including those of ghosts, spirits, and near-death experiences). The findings of this review have potential clinical implications such as reducing misdiagnosis and treatment development and provide foundations for further research. Our findings also highlight the importance of understanding why so many people report 'things that go bump in the night'.

Awake or Sleeping? Maybe Both… A Review of Sleep-Related Dissociative States

Recent studies have begun to understand sleep not only as a whole-brain process but also as a complex local phenomenon controlled by specific neurotransmitters that act in different neural networks, which is called "local sleep". Moreover, the basic states of human consciousness-wakefulness, sleep onset (N1), light sleep (N2), deep sleep (N3), and rapid eye movement (REM) sleep-can concurrently appear, which may result in different sleep-related dissociative states. In this article, we classify these sleep-related dissociative states into physiological, pathological, and altered states of consciousness. Physiological states are daydreaming, lucid dreaming, and false awakenings. Pathological states include sleep paralysis, sleepwalking, and REM sleep behavior disorder. Altered states are hypnosis, anesthesia, and psychedelics. We review the neurophysiology and phenomenology of these sleep-related dissociative states of consciousness and update them with recent studies. We conclude that these sleep-related dissociative states have a significant basic and clinical impact since their study contributes to the understanding of consciousness and the proper treatment of neuropsychiatric diseases.

Sleep Paralysis and Lucid Dreaming-Between Waking and Dreaming: A Review about Two Extraordinary States

BACKGROUND

Sleep paralysis and lucid dreams are two states of consciousness that are connected to REM sleep but are defined by higher awareness in contrast to regular REM sleep. Despite these similarities, the two states differ widely in their emotional tone and their perceived controllability. This review aims to summarize the current research containing sleep paralysis and lucid dreams. However, given the sparsity of the research, one single topic cannot be chosen.

METHODS

Articles containing both lucid dreams as well as sleep paralysis were searched for in the following databanks: MEDLINE, Scopus, Web of Science, PsycInfo, PsycArticles, and PSYNDEX. Further, citations of the found papers were examined.

RESULTS

10 studies were included in the review. Most of the studies were surveys, but there was also a case study, a randomized trial, and an observational EEG study. The numbers of participants ranged from a single participant in the case study to 1928 participants in a survey. The main findings were that correlations between sleep paralysis and lucid dreaming were positive and significant in most of the studies.

CONCLUSIONS

There is a connection between lucid dreaming and sleep paralysis. However, research is still very limited and diverse in the methodologies used. Future research should build standardized methods for examining the two phenomena.

Sleep and dreaming in the light of reactive and predictive homeostasis

Dreams are often viewed as fascinating but irrelevant mental epihenomena of the sleeping mind with questionable functional relevance. Despite long hours of oneiric activity, and high individual differences in dream recall, dreams are lost into oblivion. Here, we conceptualize dreaming and dream amnesia as inherent aspects of the reactive and predictive homeostatic functions of sleep. Mental activity during sleep conforms to the interplay of restorative processes and future anticipation, and particularly during the second half of the night, it unfolds as a special form of non-constrained, self-referent, and future-oriented cognitive process. Awakening facilitates constrained, goal-directed prospection that competes for shared neural resources with dream production and dream recall, and contributes to dream amnesia. We present the neurophysiological aspects of reactive and predictive homeostasis during sleep, highlighting the putative role of cortisol in predictive homeostasis and forgetting dreams. The theoretical and methodological aspects of our proposal are discussed in relation to the study of dreaming, dream recall, and sleep-related cognitive processes.

Role of Psychologists in Pediatric Sleep Medicine

Sleep disorders commonly afflict infants, children, and adolescents and have a significant adverse impact on them and their families, sometimes to a severe degree. They can cause immediate stress and suffering and long-term loss of opportunities and potential. Many of these disorders can be well managed by the psychologist and often one is required, either as the sole provider or as an integral part of a team. Sleep disorders have a bidirectional interplay with mental health disorders. The patient may therefore present initially to the psychologist, primary care provider, or the sleep medicine specialist.

Detecting lucid dreams only by submentalis electromyography

Lucid dreams (LDs) occur when people become aware that they are dreaming. This phenomenon has a wide range of possible applications from the perspectives of psychology, training physical movements, and controlling computers while asleep, among others. However, research on LDs might lack efficiency because the standard LD verification protocol uses polysomnography (PSG), which requires an expensive apparatus and skilled staff. The standard protocol also may reduce LD-induction efficiency. The current study examines whether humans can send phasic signals through submentalis electromyography (EMG) during muscle atonia via pre-agreed chin movements (PACM). This ability would manifest both REM sleep and consciousness, which are the main features of LDs. In laboratory conditions volunteers were instructed to open their jaws three times while in an LD right after the standard verification protocol to achieve the research goal. Results: 4 of 5 volunteers proved to be in an LD using the standard protocol, and then all of them made PACM. The outcomes show that dream signals cannot be blocked in the submentalis area during muscle atonia. Also, this finding can be considered to develop a simplified, reliable LD protocol that needs only one EMG sensor. The cost of this protocol could be only a small percentage of the current protocol, making it more convenient for researchers and volunteers. It can also be used remotely by inbuilt in wearable gadgets. Considering PACM could speed up LD research and provide many discoveries and new opportunities. Also, it can be used in sleep paralysis studies.

Dreaming of the sleep lab

The phenomenon of dreaming about the laboratory when participating in a sleep study is common. The content of such dreams draws upon episodic memory fragments of the participant's lab experience, generally, experimenters, electrodes, the lab setting, and experimental tasks. However, as common as such dreams are, they have rarely been given a thorough quantitative or qualitative treatment. Here we assessed 528 dreams (N = 343 participants) collected in a Montreal sleep lab to 1) evaluate state and trait factors related to such dreams, and 2) investigate the phenomenology of lab incorporations using a new scoring system. Lab incorporations occurred in over a third (35.8%) of all dreams and were especially likely to occur in REM sleep (44.2%) or from morning naps (48.4%). They tended to be related to higher depression scores, but not to sex, nightmare-proneness or anxiety. Common themes associated with lab incorporation were: Meta-dreaming, including lucid dreams and false awakenings (40.7%), Sensory incorporations (27%), Wayfinding to, from or within the lab (24.3%), Sleep as performance (19.6%), Friends/Family in the lab (15.9%) and Being an object of observation (12.2%). Finally, 31.7% of the lab incorporation dreams included relative projections into a near future (e.g., the experiment having been completed), but very few projections into the past (2.6%). Results clarify sleep stage and sleep timing factors associated with dreamed lab incorporations. Phenomenological findings further reveal both the typical and unique ways in which lab memory elements are incorporated de novo into dreaming. Identified themes point to frequent social and skillful dream scenarios that entail monitoring of one's current state (in the lab) and projection of the self into dream environments elaborated around local space and time. The findings have implications for understanding fundamental dream formation mechanisms but also for appreciating both the advantages and methodological pitfalls of conducting laboratory-based dream collection.