Dream to Predict? REM Dreaming as Prospective Coding

Enhancing and advancing the understanding and study of dreaming and memory consolidation: Reflections, challenges, theoretical clarity, and methodological considerations

Empirical investigations that search for a link between dreaming and sleep-dependent memory consolidation have focused on testing for an association between dreaming of what was learned, and improved memory performance for learned material. Empirical support for this is mixed, perhaps owing to the inherent challenges presented by the nature of dreams, and methodological inconsistencies. The purpose of this paper is to address critically prevalent assumptions and practices, with the aim of clarifying and enhancing research on this topic, chiefly by providing a theoretical synthesis of existing models and evidence. Also, it recommends the method of Targeted Memory Reactivation (TMR) as a means for investigating if dream content can be linked to specific cued activations. Other recommendations to enhance research practice and enquiry on this subject are also provided, focusing on the HOW and WHY we search for memory sources in dreams, and what purpose (if any) they might serve.

The hypnagogic state: A brief update

The hypnagogic state refers to a transitional stage between wakefulness and sleep, in which sensory perceptions can be experienced. In this review, we compile and discuss the recent scientific literature on hypnagogia research regarding the future directions proposed by Schacter (1976; Psychological Bulletin, 83, 452). After a short introduction discussing the terminology used in hypnagogia research and the differentiation of hypnagogic states with other related phenomena, we review the reported prevalence of hypnagogic states. Then, we evaluate the six future directions suggested by Schacter and we propose three further future directions. First, a better understanding of the emotional quality of hypnagogic states is needed. Second, a better understanding of why hypnagogic states occur so frequently in the visual and kinaesthetic modalities is needed. Lastly, a better understanding of the purpose of hypnagogic states is needed. In conclusion, research has made great progress in recent years, and we are one step closer to demystifying the hypnagogic state.

Learning cortical representations through perturbed and adversarial dreaming

Humans and other animals learn to extract general concepts from sensory experience without extensive teaching. This ability is thought to be facilitated by offline states like sleep where previous experiences are systemically replayed. However, the characteristic creative nature of dreams suggests that learning semantic representations may go beyond merely replaying previous experiences. We support this hypothesis by implementing a cortical architecture inspired by generative adversarial networks (GANs). Learning in our model is organized across three different global brain states mimicking wakefulness, non-rapid eye movement (NREM), and REM sleep, optimizing different, but complementary, objective functions. We train the model on standard datasets of natural images and evaluate the quality of the learned representations. Our results suggest that generating new, virtual sensory inputs via adversarial dreaming during REM sleep is essential for extracting semantic concepts, while replaying episodic memories via perturbed dreaming during NREM sleep improves the robustness of latent representations. The model provides a new computational perspective on sleep states, memory replay, and dreams, and suggests a cortical implementation of GANs.

Constructive episodic simulation in dreams

Memories of the past help us adaptively respond to similar situations in the future. Originally described by Schacter & Addis in 2007, the "constructive episodic simulation" hypothesis proposes that waking thought combines fragments of various past episodes into imagined simulations of events that may occur in the future. This same framework may be useful for understanding the function of dreaming. N = 48 college students were asked to identify waking life sources for a total of N = 469 dreams. Participants frequently traced dreams to at least one past or future episodic source (53.5% and 25.7% of dreams, respectively). Individual dreams were very often traced to multiple waking sources (43.9% of all dreams with content), with fragments of past memory incorporated into scenarios that anticipated future events. Waking-life dream sources are described in terms of their phenomenology and distribution across time and sleep stage, providing new evidence that dreams not only reflect the past, but also utilize memory in simulating potential futures.

Dissociation and Dissociative Disorders Reconsidered: Beyond Sociocognitive and Trauma Models Toward a Transtheoretical Framework

For more than 30 years, the posttraumatic model (PTM) and the sociocognitive model (SCM) of dissociation have vied for attention and empirical support. We contend that neither perspective provides a satisfactory account and that dissociation and dissociative disorders (e.g., depersonalization/derealization disorder, dissociative identity disorder) can be understood as failures of normally adaptive systems and functions. We argue for a more encompassing transdiagnostic and transtheoretical perspective that considers potentially interactive variables including sleep disturbances; impaired self-regulation and inhibition of negative cognitions and affects; hyperassociation and set shifts; and deficits in reality testing, source attributions, and metacognition. We present an overview of the field of dissociation, delineate uncontested and converging claims across perspectives, summarize key multivariable studies in support of our framework, and identify empirical pathways for future research to advance our understanding of dissociation, including studies of highly adverse events and dissociation. Expected final online publication date for the Annual Review of Clinical Psychology, Volume 18 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Balancing Prediction and Surprise: A Role for Active Sleep at the Dawn of Consciousness?

The brain is a prediction machine. Yet the world is never entirely predictable, for any animal. Unexpected events are surprising, and this typically evokes prediction error signatures in mammalian brains. In humans such mismatched expectations are often associated with an emotional response as well, and emotional dysregulation can lead to cognitive disorders such as depression or schizophrenia. Emotional responses are understood to be important for memory consolidation, suggesting that positive or negative 'valence' cues more generally constitute an ancient mechanism designed to potently refine and generalize internal models of the world and thereby minimize prediction errors. On the other hand, abolishing error detection and surprise entirely (as could happen by generalization or habituation) is probably maladaptive, as this might undermine the very mechanism that brains use to become better prediction machines. This paradoxical view of brain function as an ongoing balance between prediction and surprise suggests a compelling approach to study and understand the evolution of consciousness in animals. In particular, this view may provide insight into the function and evolution of 'active' sleep. Here, we propose that active sleep - when animals are behaviorally asleep but their brain seems awake - is widespread beyond mammals and birds, and may have evolved as a mechanism for optimizing predictive processing in motile creatures confronted with constantly changing environments. To explore our hypothesis, we progress from humans to invertebrates, investigating how a potential role for rapid eye movement (REM) sleep in emotional regulation in humans could be re-examined as a conserved sleep function that co-evolved alongside selective attention to maintain an adaptive balance between prediction and surprise. This view of active sleep has some interesting implications for the evolution of subjective awareness and consciousness in animals.

Increased creative thinking in narcolepsy

Some studies suggest a link between creativity and rapid eye movement sleep. Narcolepsy is characterized by falling asleep directly into rapid eye movement sleep, states of dissociated wakefulness and rapid eye movement sleep (cataplexy, hypnagogic hallucinations, sleep paralysis, rapid eye movement sleep behaviour disorder and lucid dreaming) and a high dream recall frequency. Lucid dreaming (the awareness of dreaming while dreaming) has been correlated with creativity. Given their life-long privileged access to rapid eye movement sleep and dreams, we hypothesized that subjects with narcolepsy may have developed high creative abilities. To test this assumption, 185 subjects with narcolepsy and 126 healthy controls were evaluated for their level of creativity with two questionnaires, the Test of Creative Profile and the Creativity Achievement Questionnaire. Creativity was also objectively tested in 30 controls and 30 subjects with narcolepsy using the Evaluation of Potential Creativity test battery, which measures divergent and convergent modes of creative thinking in the graphic and verbal domains, using concrete and abstract problems. Subjects with narcolepsy obtained higher scores than controls on the Test of Creative Profile (mean ± standard deviation: 58.9 ± 9.6 versus 55.1 ± 10, P = 0.001), in the three creative profiles (Innovative, Imaginative and Researcher) and on the Creative Achievement Questionnaire (10.4 ± 25.7 versus 6.4 ± 7.6, P = 0.047). They also performed better than controls on the objective test of creative performance (4.3 ± 1.5 versus 3.7 ± 1.4; P = 0.009). Most symptoms of narcolepsy (including sleepiness, hypnagogic hallucinations, sleep paralysis, lucid dreaming, and rapid eye movement sleep behaviour disorder, but not cataplexy) were associated with higher scores on the Test of Creative Profile. These results highlight a higher creative potential in subjects with narcolepsy and further support a role of rapid eye movement sleep in creativity.

Current approaches to modeling the virtual reality in rodents for the assessment of brain plasticity and behavior

Virtual reality (VR) and augmented reality (AR) have become valuable tools to study brains and behaviors resulting in development of new methods of diagnostics and treatment. Neurodegenerаtion is one of the best examples demonstrating efficacy of VR/АR technologies in modern neurology. Development of novel VR systems for rodents and combination of VR tools with up-to-date imaging techniques (i.e. MRI, imaging of neural networks etc.), brain electrophysiology (EEG, patch-clamp), precise analytics (microdialysis) allowed implementing of VR protocols into the animal neurobiology to study brain plasticity, sensorimotor integration, spatial navigation, memory, and decision-making. VR/AR for rodents is а young field of experimental neuroscience and has already provided more consistent testing conditions, less human-animal interaction, opportunities to use a wider variety of experimental parameters. Here we discuss present and future perspectives of using VR/AR to assess brain plasticity, neurogenesis and complex behavior in rodent and human study, and their advantages for translational neuroscience.

The role of sleep in the formation and updating of abstract mental representations

According to Gilead and colleagues, to be efficient abstraction requires a hierarchical organization of information into long-term memory. But, how and when are abstract representations consolidated into long-term memory and how are they integrated with pre-existing abstracta are questions not discussed by Gilead and colleagues. Here, we propose that these processes occur preferentially during offline periods such as sleep.

Measuring Counterintuitiveness in Supernatural Agent Dream Imagery

The present article tests counterintuitiveness theory and methodology in relation to religious dream imagery using data on religious dream content. The endeavor adopts a "fractionated" or "piecemeal" approach where supernatural agent (SA) cognition is held to be a pivotal building block of purportedly religious dreaming. Such supernaturalistic conceptualizations manifest in a cognitive environment of dream simulation processes, threat detection, and violation of basic conceptual categorization characterized by counterintuitiveness. By addressing SA cognitions as constituents of allegedly religious dream imagery, additional theorizing and supporting data are presented in a growing body of research in the cognitive science of religion (e.g., Barrett et al., 2009;Hornbeck and Barrett, 2013;Barrett, 2017) and on religious dreaming (McNamara and Bulkeley, 2015;McNamara, 2016). The aim of the article is partly to map and align contemporary theorizing regarding counterintuitiveness and CI schemes with empirical qualification of the prosaic hypothesis about the predominance of supernaturalism in allegedly religious dreaming. This is done by (1) exploring the crucial topic of the pervasiveness of cognitive counterintuitiveness; (2) testing Barrett's counterintuitiveness coding and quantifying scheme (CI scheme) for counterintuitiveness in the context of religious dreaming by assessing intercoder reliability; and (3) exploring the prevalence and base rate frequency of counterintuitiveness in dream reports. This undertaking aims to contribute to the methodology and understanding of religious dream cognition, as well as to establish the cross-cultural base rates of counterintuitiveness in dreams for future research.

Dreams and Psychedelics: Neurophenomenological Comparison and Therapeutic Implications

BACKGROUND

A resurgence of neurobiological and clinical research is currently underway into the therapeutic potential of serotonergic or 'classical' psychedelics, such as the prototypical psychedelic drug lysergic acid diethylamide (LSD), psilocybin (4-phosphoryloxy-N,Ndimethyltryptamine), and ayahuasca - a betacarboline- and dimethyltryptamine (DMT)-containing Amazonian beverage. The aim of this review is to introduce readers to the similarities and dissimilarities between psychedelic states and night dreams, and to draw conclusions related to therapeutic applications of psychedelics in psychiatry.

METHODS

Research literature related to psychedelics and dreaming is reviewed, and these two states of consciousness are systematically compared. Relevant conclusions with regard to psychedelicassisted therapy will be provided.

RESULTS

Common features between psychedelic states and night dreams include perception, mental imagery, emotion activation, fear memory extinction, and sense of self and body. Differences between these two states are related to differential perceptual input from the environment, clarity of consciousness and meta-cognitive abilities. Therefore, psychedelic states are closest to lucid dreaming which is characterized by a mixed state of dreaming and waking consciousness.

CONCLUSION

The broad overlap between dreaming and psychedelic states supports the notion that psychedelics acutely induce dreamlike subjective experiences which may have long-term beneficial effects on psychosocial functioning and well-being. Future clinical studies should examine how therapeutic outcome is related to the acute dreamlike effects of psychedelics.