Dreamed movement elicits activation in the sensorimotor cortex

Since the discovery of the close association between rapid eye movement (REM) sleep and dreaming, much effort has been devoted to link physiological signatures of REM sleep to the contents of associated dreams [1-4]. Due to the impossibility of experimentally controlling spontaneous dream activity, however, a direct demonstration of dream contents by neuroimaging methods is lacking. By combining brain imaging with polysomnography and exploiting the state of "lucid dreaming," we show here that a predefined motor task performed during dreaming elicits neuronal activation in the sensorimotor cortex. In lucid dreams, the subject is aware of the dreaming state and capable of performing predefined actions while all standard polysomnographic criteria of REM sleep are fulfilled [5, 6]. Using eye signals as temporal markers, neural activity measured by functional magnetic resonance imaging (fMRI) and near-infrared spectroscopy (NIRS) was related to dreamed hand movements during lucid REM sleep. Though preliminary, we provide first evidence that specific contents of REM-associated dreaming can be visualized by neuroimaging.     

Mental Processes and the Brain During Dreams.

This article examines the different theoretical approaches to dreaming and compares them with recent data from brain-mapping studies. Two lines of investigation were considered: a neurobiological and a cognitive approach. Both lines of investigation can be usefully integrated into recent research using the techniques of brain mapping. Two aspects of particular interest are discussed: (a) The pattern of limbic and paralimbic activation in rapid eye movement (REM) and non-REM could explain some differences of oneiric hallucination during different stages of sleep, and (b) the deactivation of the heteromodal cortex could explain the loss of reality testing and the absence of self-consciousness during dreams. The complex nature of the dreaming phenomenon makes it necessary to distinguish clearly between mental representation and the underlying neurobiological changes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Austrian Dream Behavior: Results of a Representative Population Survey

This study was based on a survey of a representative sample of 1000 Austrians who were questioned about their sleep and dream behavior. About two-thirds of the respondents reported that they generally recalled at least one dream per month. Dream recall frequency decreased with advancing age, but did not differ between men and women. Fifty-five percent of the respondents characterized the affective content of their dreams: 29% reported neutral, 20% positive, and 6% negative dreams. Four percent of the sample reported suffering from nightmares. These respondents more frequently reported snoring, interrupted sleep, daytime somnolence, anxiety and nervousness, depression, high dream recall, recurrent dreams, and dreaming in color. Twenty-six percent of the total sample reported that sometimes they realized during their dreams that they were dreaming. These respondents more frequently reported family problems, high dream recall, positive dream content, recurrent dreams, dreaming in color, and nightmares.     

Dream recall after night awakenings from tonic/phasic REM sleep

Eleven healthy subjects, 9 females and 2 males aged 21-23, were submitted to all night polygraphic recording and awaken in REM (Rapid Eye Movements) sleep, randomly upon tonic or phasic REM. Immediately upon awakening subjects were asked about possible dreaming according to the standardized questionnaire. Seventy-seven dreams, i.e. 79% of all 97 REM awakenings, were reported and analyzed. There were no significant differences in reported frequency of dreamings after awakening, mood and dream content due to phasic/tonic REM sleep. Dreams from phasic REM were a bit more colorful. Predictor of morning remembering of dreams was meaninglessness, not meaningfulness of dreams, and, in lesser extent, good mood, colorfulness, dreams with words and phasic REM sleep.     

Representation of the self in REM and NREM dreams.

The authors hypothesized that representations of the Self (or the dreamer) in dreams would change systematically, from a prereflective form of Self to more complex forms, as a function of both age and sleep state (REM vs. non-REM). These hypotheses were partially confirmed. While the authors found that all the self-concept-related dream content indexes derived from the Hall/Van de Castle dream content scoring system did not differ significantly between the dreams of children and adults, adult Selves were more likely to engage in "successful" social interactions. The Self never acted as aggressor in NREM dream states and was almost always the befriender in friendly interactions in NREM dreams. Conversely, the REM-related dream Self preferred aggressive encounters. Our results suggests that while prereflective forms of Self are the norm in children's dreams, two highly complex forms of Self emerge in REM and NREM dreams. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigation of dream reports after transcranial direct current stimulation (tDCs) during slow wave sleep (SWS)

Despite being a prominent feature of REM sleep, dreams have also been reported from NREM sleep. Neuroimaging studies have revealed regional patterns of brain activation and deactivation during REM and NREM sleep, with frontal and posterior parietal cortices implicated as brain regions involved in dreaming. From our recent stage 2 study it was revealed that tDCs of these brain regions during this stage of sleep resulted in an increase in reported dream imagery. Thus, the aim of this study was to investigate the effect of simultaneous anodal and cathodal tDCs applied to the right posterior parietal and frontal cortex (respectively) during SWS on dream recall. After 60 s of continuous SWS, participants were administered either tDCs, low tDCs, or blank control, followed by a 60 s delay period to confirm SWS before waking the participant for dream report collection. These conditions were administered in a counterbalanced order across the night. Analyses revealed no significant difference between conditions in the three dream measures. However, an analysis of visualizable nouns to total words revealed a significantly higher ratio in the low tDCs condition compared to the tDCs condition. It was concluded that tDCs had no appreciable effect on reported dream imagery. However, such findings are preliminary as they are from a research protocol which is in the process of refinement with more definitive results expected in future. Thus, further studies should now investigate the application of tDCs using improved methodologies and to other cortical regions implicated in the process of dreaming.

     

In Bed With Mark Solms? What a Nightmare! A Reply to Domhoff (2005).

Bill Domhoff (2005) has challenged the activation synthesis model of dreaming on the basis of a misreading of the neurobiological literature and an individualistic view of dream psychology (see record 2005-02950-001). The author begins his reply by clarifying and emphasizing the formal approach to dream cognitions. Instead of focusing on the individual aspects of dreaming that interest Domhoff, activation synthesis strives to identify and measure the generic differences that characterize all dreams and that are likely to correlate with the neurobiological findings. He then goes on to point out that such formal features as the visuomotor imagery, the emotional intensification, and the defective cognition of dreams do correlate with the cellular and molecular neurobiological data from animal studies and with the brain imaging and lesion data from human studies. Individual differences may also exist but these are not relevant to the main task of sleep psychophysiology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessing the dream-lag effect for REM and NREM stage 2 dreams

This study investigates evidence, from dream reports, for memory consolidation during sleep. It is well-known that events and memories from waking life can be incorporated into dreams. These incorporations can be a literal replication of what occurred in waking life, or, more often, they can be partial or indirect. Two types of temporal relationship have been found to characterize the time of occurrence of a daytime event and the reappearance or incorporation of its features in a dream. These temporal relationships are referred to as the day-residue or immediate incorporation effect, where there is the reappearance of features from events occurring on the immediately preceding day, and the dream-lag effect, where there is the reappearance of features from events occurring 5-7 days prior to the dream. Previous work on the dream-lag effect has used spontaneous home recalled dream reports, which can be from Rapid Eye Movement Sleep (REM) and from non-Rapid Eye Movement Sleep (NREM). This study addresses whether the dream-lag effect occurs only for REM sleep dreams, or for both REM and NREM stage 2 (N2) dreams. 20 participants kept a daily diary for over a week before sleeping in the sleep laboratory for 2 nights. REM and N2 dreams collected in the laboratory were transcribed and each participant rated the level of correspondence between every dream report and every diary record. The dream-lag effect was found for REM but not N2 dreams. Further analysis indicated that this result was not due to N2 dream reports being shorter, in terms of number of words, than the REM dream reports. These results provide evidence for a 7-day sleep-dependent non-linear memory consolidation process that is specific to REM sleep, and accord with proposals for the importance of REM sleep to emotional memory consolidation.     

Dreaming and schizophrenia: a common neurobiological background?

Normal waking mentation is the outcome of the combined action of both electrophysiological and neurochemical antagonistic and complementary activating and inhibitory influences occurring mainly in the cerebral cortex. The chemical ones are supported principally by acetylcholine, and noradrenaline and serotonin, respectively. During rapid eye movement (REM) sleep, the monoaminergic silence - except dopaminergic ongoing activity - disrupts this equilibrium and seems to be responsible for disturbances of mental activity characteristic of dreaming. This imbalance could cause disconnectivity of cortical areas, failure of latent inhibition and possibly the concomitant prefrontal dorsolateral deactivation. Moreover, the decrease of prefrontal dopaminergic functioning could explain the loss of reflectiveness in this sleep stage. All these phenomena are also encountered in schizophrenia. The psychotic-like mentation of dreaming (hallucinations, delusions, bizarre thought processes) could result from the disinhibition of dopamine influence in the nucleus accumbens by the noradrenergic and serotonergic local silence and/or the lifting of glutamate influence from the prefrontal cortex and hippocampus. We hypothesize that, during REM sleep, the increase of dopamine and the decrease of glutamate release observed in nucleus accumbens reach the threshold values at which psychotic disturbances arise during wakefulness. Whatever the precise mechanism, it seems that the functional state of the prefrontal cortex and nucleus accumbens is the same during dreaming sleep stage and in schizophrenia. The convergent psychological, electrophysiological, tomographic, pharmacological and neurochemical criteria of REM sleep and schizophrenia suggest that this sleep stage could become a good neurobiological model of this psychiatric disease.     

Psychophysiological correlates of lucid dreaming.

The main goal of the present study was to explore electrophysiological differences between lucid and nonlucid dreams in REM sleep. Seven men and four women experienced in lucid dreaming underwent polysomnographic recordings in the sleep laboratory on two consecutive nights. EEG signals were subjected to spectral analysis to obtain five different frequency bands between 1 and 20 Hz. Lucidity was determined by both subjective dream reports and eye-movement signals made by the subjects in response to light stimuli indicating a REM period. The main discrimination factor between lucid and nonlucid dreaming was found in the beta-1 frequency band (13-19 Hz), which in lucid dreaming was increased in both parietal regions. The ratio of frontal to parietal beta-1 activity was 1 to 1.16 in nonlucid and 1 to 1.77 in lucid dreaming. A tendency towards the greatest increase was observed in the left parietal lobe (P3), an area of the brain considered to be related to semantic understanding and self-awareness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Meteorite or gemstone? Dreaming as one end of a continuum of functioning: Implications for research and for the use of dreams in therapy and self-knowledge.

Is a dream a meteorite—a bit of material arriving from a distant place that needs to be carefully analyzed to give us knowledge about that place (outside or inside us)? Is it a strange text which has come to us in a foreign language, that needs to be translated into our own? This “meteorite view” is held by some religious and spiritual persons, by many orthodox psychoanalysts and other therapists, and implicitly by many researchers. They all see the dream as something alien, something totally different from our ordinary mental functioning. This paper presents a great deal of research favoring an alternate view—that the dream is an earth-stone, not an alien stone. It may be impressive and beautiful (gemstone), but it's still an earth-stone. The dream is part of our mental functioning. It is one end of a continuum, running from focused waking thought, through looser thought, fantasy, daydreaming, reverie and dreaming. We review reasons why dreams are often considered “totally different”: they're perceptual, not conceptual; they're bizarre; they are “so real”; they're so easily forgotten; they're involuntary; they occur in REM sleep—a totally different state. We demonstrate that none of these reasons are persuasive. In each sense, there is overlap between dreams and other forms of functioning. The continuum view leads to different kinds of research and a different style of dreamwork. It also helps answer questions the field has long struggled with including: Should we study “a dream” or “dreaming”? Are dreams meaningful or meaningless? (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dreaming as Delirium: A Reply to Bert States

When analyzed from a formal mental states point of view, REM sleep dreaming evinces all four of the cardinal defining features of delirium: visual halluncinosis; disorientation; memory loss, and confabulation. This new formulation is supported by neurobiological findings at the level of neurones and neuromodulators, which indicate a dramatic shift in the balance of the same aminergic and cholinergic neuromodulatory systems that mediate delirium upon the ingestion or withdrawal of drugs that upset that balance. Convinced that all of the symptoms and signs of delirium that have been emphasized above could be the natural manifestations of hyperassociation, Bert States has challenged both the validity and heuristic value of this Dreaming as Delirium paradigm. Arguing that no natural process like dreaming can be dysfunctional, and wishing to advance the thesis that all naturally determined mental content obeys the law of associativity, States commits himself to a paradigm of interpretability which is linked to a metaphorical-analogical function of memory. States (and most other students of dreaming) have difficulty accepting my claim that discontinuity and incongruity are in a dialectical and oppositional struggle with associativity. These dissociative processes, which arise at the neuronal level described by the reciprocal interaction model, translate into the universal and generically nonsensical aspects of dream content that are explained by the paradigm of dreaming as delirium. In this essay, I urge that States and all others who share with me the fond hope of a scientifically respectable approach to the interpretation of dreams, recognize that both associativity and dissociation are hard at work in REM sleep dreaming and other autocreative states of mind. Once the both/and replaces the either/or mind set, it is possible to separate the emotionally salient signals from the cognitively disjunctive noise. The same step allows us to recognize that all complex natural systems have both functional and dysfunctional aspects and that these are sometime mutually enhancing as well as mutually entailed by the mechanisms that engender them. Turning Polonius on his head I thus suggest: Though this be method, yet there's madness in it!     

Effects of Somatosensory Stimulation on Dream Content in Gymnasts and Control Participants: Evidence of Vestibulomotor Adaptation in REM Sleep

Somatosensory stimulation of the leg muscles in REM sleep appears to perturb virtual orientation in dream experiences. According to our model of vestibulomotor adaptation (Sauvageau, Nielsen, & Montplaisir, 1996), the dreaming mind attempts to compensate for such destabilizing stimulation by increasing eye movement activity or by modifying dream content, among other possible reactions. Effective compensation may be more easily achieved by participants who are adapted to the disruptive stimulation or who possess highly developed vestibulomotor skills. To examine this possibility, we studied the effects of Somatosensory stimulation on the dreams of 6 gymnasts and 6 control participants aged 9 to 16 years. Results provide some support for the expectations that 1) imposed Somatosensory information is processed by the central nervous system in REM sleep, 2) unilateral stimulation induces an upset in virtual orientation, 3) gymnasts are more resistant to these disruptive effects of stimulation than are control participants, and 4) because of long-term adaptation, the dream content of gymnasts does not differ markedly from that of controls. Though preliminary and in need of replication, the findings are compatible with the notion that the developed vestibular skills of gymnasts protects them to some extent from the effects of a disruptive Somatosensory stimulus during sleep.     

A reply to Hobson (2005).

J. A. Hobson's (2005) commentary merely repeats his past theoretical assertions (see record 2005-02950-002). It asks questions that rest on the refuted hypothesis that real dreaming occurs only in REM sleep and that are already answered in the author's critique. Despite many studies, there is still no evidence that neurophysiological changes during REM are responsible for any unique formal features in dreams. As for the psychological consequences of the neuromodulatory environment during REM, there are no studies. Most important, Hobson overlooks a key point in regard to a new neurocognitive approach to dreams: The many parallels between dreaming and waking cognition raise the intriguing possibility that relatively small changes from waking to sleeping can account for the unique features of dreams, rendering his REM-based speculations irrelevant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of The Mind at Night: The New Science of How and Why We Dream.

In this article I review "The Mind at Night: The New Science of How and Why We Dream," written by Andrea Rock. To begin with this book is an exciting journey through modern dream research. Scientific facts, which are skillfully explained, are complemented by personal accounts of well-known researchers in the field obtained through interviews. The diversity of the themes addressed in the book (e.g., sleep and memory, animal research, imaging studies, dream content analysis, consciousness research, creativity, and lucid dreaming) clearly shows the extensive "detective work" the author has accomplished. The major problem I had--as a researcher in this field--was the structure, or the lack of structure, within the book. Because of the way the book is organized, I decided to structure this review along the following themes: REM sleep, REM sleep and dreaming, biology of dreaming, dream content findings, and the integration of dream research into cognitive neuroscience in general. Despite the lack of structure of the book, Andrea Rock has written a wonderful book about modern dream research that is stimulating for researchers as well as for interested lay persons. I recommend it to everyone who is interested in dream research, the old question of the mind-body relationship, or understanding consciousness in general. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The 'scanning hypothesis' of rapid eye movements during REM sleep: a review of the evidence

Rapid eye movements (REMs) and visual dreams are salient features of REM sleep. However, it is unclear whether the eyes scan dream images. Several lines of evidence oppose the scanning hypothesis: REMs persist in animals and humans without sight (pontine cats, foetus, neonates, born-blinds), some binocular REMs are not conjugated (no focus point), REMs occur in parallel (not in series) with the stimulation of the visual cortex by ponto-geniculo-occipital spikes, and visual dreams can be obtained in non REM sleep. Studies that retrospectively compared the direction of REMs to dream recall recorded after having awakened the sleeper yielded inconsistent results, with a concordance varying from 9 to 80%. However, this method was subject to methodological flaws, including the bias of retrospection and neck atonia that does not allow the determination of the exact direction of gaze. Using the model of RBD (in which patients are able to enact their dreams due to the absence of muscle atonia) in 56 patients, we directly determined if the eyes moved in the same directions as the head and limbs. When REMs accompanied goal-oriented motor behaviour during RBD (e.g., framing something, greeting with the hand, climbing a ladder), 90% were directed towards the action of the patient (same plane and direction). REMs were however absent in 38% of goal-oriented behaviours. This directional coherence between limbs, head and eye movements during RBD suggests that, when present, REMs imitate the scanning of the dream scene. Because REMs index and complexity were similar in patients with RBD and controls, this concordance can be extended to normal REM sleep. These results are consistent with the model of a brainstem generator activating simultaneously images, sounds, limbs movements and REMs in a coordinated parallel manner, as in a virtual reality.     

A New Neurocognitive Theory of Dreams

Discoveries in three distinct areas of dream research make it possible to suggest the outlines of a new neurocognitive theory of dreaming. The first relevant findings come from assessments of patients with brain injuries, which show that lesions in different areas have differential effects on dreaming and thereby imply the contours of the neural network necessary for dreaming. The second set of results comes from work with children ages 3–15 in the sleep laboratory, which reveals that only 20–30% of REM period awakenings lead to dream reports up to age 9 and that the dreams of children under age 5 are bland and static in content. The third set of findings comes from a rigorous system of content analysis, which demonstrates the repetitive nature of much dream content and that dream content in general is continuous with waking conceptions and emotional preoccupations. Based on these findings, dreaming is best understood as a developmental cognitive achievement that depends upon the maturation and maintenance of a specific network of forebrain structures. The output of this neural network for dreaming is guided by a continuity principle linked to current personal concerns on the one hand and a repetition principle rooted in past emotional preoccupations on the other.     

Refocusing the Neurocognitive Approach to Dreams: A Critique of the Hobson Versus Solms Debate.

This article examines the ongoing debate between activation-synthesis theorist J. Allan Hobson and psychoanalytic theorist Mark Solms about the nature of dreaming and dream content. After discussing their neurophysiological disagreements, it argues that they are more similar than different in some important ways, especially in talking about dreams in the same breath as psychosis and in drawing conclusions about dream content on the basis of their neurophysiological assumptions, without any reference to the systematic findings on the issue. Evidence from inside and outside the sleep laboratory on the coherent nature of most dreams is presented to demonstrate that neither theorist is on solid ground in his main assertions. Dreaming is usually a far more realistic and understandable enactment of interests and concerns than the 2 researchers assume. In addition, several of Hobson's and Solms's claims concerning the neural basis of dreaming are challenged on the basis of neurophysiological evidence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotions in the Diary and REM Dreams of Young and Late Adulthood Women and Their Relation to Life Satisfaction.

Expanding on studies of the incidence and valence of emotions in dreams and their relationship with waking life satisfaction, home and rapid eye movement (REM) sleep dreams were collected from 30 late adulthood and 28 young women who had filled out a life satisfaction scale. Four positive and 4 negative dream emotions were self-rated. Both groups reported more emotions, with greater intensity, in home dreams than in REM dreams, particularly the older group. Regardless of age, intensity of negative emotions was lower in laboratory dreams than in home dreams, but there was no difference for positive emotions. The older women's home dreams had fewer negative emotions, with lower intensity, than did the young women's. Life satisfaction did not differ between age groups and was not significantly related to dream emotions. These results reinforce the distinction between home and laboratory dreams and question the relation between dream emotions and life satisfaction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Why Did Empirical Dream Researchers Reject Freud? A Critique of Historical Claims by Mark Solms.

Neuropsychologist and psychoanalyst Mark Solms (1997) made a major contribution to dream research through his clinico-anatomical studies, which reveal the outlines of the neural network that underlies dreaming. However, in more recent work (see record 2002-17656-000) he misunderstands the history of the rapid eye movement (REM)/non-REM (NREM) controversy in a Freudian-serving way and ignores the considerable systematic empirical evidence that contradicts the key claims of the Freudian dream theory he is trying to revive. After summarizing Solms's claims about the history of laboratory dream research, this article suggests a different version of that history and summarizes the empirical findings that explain why Freudian theory is not considered viable by most dream researchers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)