- Dream & Nightmare Laboratory
Center for Advanced Research in Sleep Medicine,
Hopital du Sacre-Coeur de Montreal,
5400 boul. Gouin Ouest
Montreal, Quebec, Canada H4J 1C5
Tore Nielsen
Université de Montréal, Psychiatry, Faculty Member
- Learning & Memory, Neurobiology of Learning and Memory, Memory (Cognitive Psychology), Embodiment, Blindness, Brain Imaging, and 28 moreSleep and Dreaming, Calorie restriction, Anthropology of Dreams and Dreaming, Nightmares, Metabolic Effects of Fasting, Dreams (History), Dreaming, Dreams, Alexithymia, Feasting and Fasting, Sleep Physiology, Dreams (Psychology), Sleep Paralysis, Visions And Dreams, Sleep history, Mesopotamian dream gods, Sleep Medicine, Online Identity and Presence, Sleep & Circadian Rhythms, Mirror Neurons, Philosophy of dream, Effect of Dreams of the Neurological status, Transcranial Direct Current Stimulation, Animism, Phenomenology of the Body (Philosophy), Sense of Place, Being-at-Home, and Wordstatedit
- Dedicated to dream research in all its aspects. I run a sleep lab for cognitive testing (including a VR room) and bio... moreDedicated to dream research in all its aspects. I run a sleep lab for cognitive testing (including a VR room) and biorecording (EEG, EMG, ECG, HR, respiration, etc.). Nightmares and sleep onset imagery are current areas of focus.
I have a side interest in the effects of intermittent fasting and caloric restriction on health and longevity.
I write. I write. I write. I write!edit
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... more
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 dream-ing'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.
Research Interests: Consciousness, Self Observation, Introspection, Sleep & Circadian Rhythms, Consciousness Studies, and 9 moreDreaming, Sleep and Dreaming, Multisensory Integration, Sleep, Psychology of Sleep and Dreaming, Sleep Onset, Hypnagogic Imagery, Dreams, Consciousness Studies, Qualitative Research, and Introspective Research Methods
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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... more
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 polysomno-graphy, 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 correlations with all of these measures, partialing out slow spindles attenuated, but did not eliminate, the fast spindle correlations. Results are largely consistent with the conclusion that fast sleep spindles are associated with a common trait factor that also influences dream recall. However, the results also raise the possibility that both spindles and dreaming are expressions of memory consolidation mechanisms, such as neural replay, that transcend sleep stage.
Research Interests: Memory (Cognitive Psychology), Collective Memory, Memory, Dreaming, Sleep and Dreaming, and 7 moreNightmares, Brain Plasticity, Psychology of Sleep and Dreaming, Sleep and Memory Consolidation, Don’t waste your life focusing on the bad things and what people tell you that you could never do, look at all the good things and all the paths you could follow to fulfill your dreams., Dreams, Nightmares, and Sleep Spindles
Nightmares (NM) are characterized by intense negative emotion. Research suggests that frequent NM sufferers also have greater inclinations to fantasy and dream-like daydreams, although it is not known whether they experience intense... more
Nightmares (NM) are characterized by intense negative emotion. Research suggests that frequent NM sufferers also have greater inclinations to fantasy and dream-like daydreams, although it is not known whether they experience intense negative emotion as part of these waking state cognitions. We assessed the daydreams and nap dreams of NM participants to determine whether they have more negative daydream content and more vivid imagery overall. NM and control (CTL) participants completed a daydream procedure followed by a nap targeted to contain 80 min total sleep time and an awakening 10 min into rapid eye movement (REM) sleep. For both daydreams and nap dreams, participants completed a questionnaire regarding 4 factors: negativity, positivity, body sensation, and bizarreness. Results revealed the NM group had elevated positivity, body sensation and bizarreness ratings for daydreams compared with the CTL group, but did not differ from them for negativity ratings. NM participants also had elevated body sensation ratings for nap dreams, but did not differ for negativity, positivity, or bizarreness. Thus, while NMs themselves are characterized by negative affect, NM sufferers nonetheless have higher than
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Background: Sleep disordered breathing is frequently observed in patients with cardiovascular disease. Even in the absence of heart disease, acute and chronic hypoxia have been shown to promote sleep-related periodic breathing with... more
Background: Sleep disordered breathing is frequently observed in patients with cardiovascular disease. Even in the absence of heart disease, acute and chronic hypoxia have been shown to promote sleep-related periodic breathing with central apnea characterized by a repetitive reduction or lack of respiratory activity. Cyanotic congenital heart disease (CCHD) is associated with chronic hypoxia, regardless of whether an increase in pulmonary artery pressures coexists. Sleep aggravated hypoxia has been observed in many such patients, but it remains to be determined whether sleep disordered breathing is contributory. We, therefore, sought to assess sleep-related breathing pattern in patients with CCHD.
Methods: Adults with CCHD, resting arterial oxygen saturation b90%, and systemic ejection fraction N40% were prospectively enrolled in a cross-sectional study. To assess sleep and respiratory indices, subjects underwent a standardized clinical appraisal that included arterial blood gas analysis and a comprehensive sleep study with an ambulatory device. An apnea–hypopnea index (AHI) ≥5/h was considered to indicate sleep apnea.
Results: Ten adults with CCHD, aged 38±11 years, completed the study. Seven patients had elevated pulmonary artery pressures, with a mean systolic pressure of 86.3±18.1 mm Hg. All patients demonstrated normal sleep parameters. Oxygen saturation further declined in 5 patients during sleep. However, no associated alteration in respiratory parameters was observed and no significant arrhythmia. The mean AHI was 1.1±1.0/h. No subject met the pre-defined criterion for sleep apnea.
Conclusion: Although further oxygen desaturation may be observed during sleep in patients with CCHD, it occurs in the absence of sleep disordered breathing.
Methods: Adults with CCHD, resting arterial oxygen saturation b90%, and systemic ejection fraction N40% were prospectively enrolled in a cross-sectional study. To assess sleep and respiratory indices, subjects underwent a standardized clinical appraisal that included arterial blood gas analysis and a comprehensive sleep study with an ambulatory device. An apnea–hypopnea index (AHI) ≥5/h was considered to indicate sleep apnea.
Results: Ten adults with CCHD, aged 38±11 years, completed the study. Seven patients had elevated pulmonary artery pressures, with a mean systolic pressure of 86.3±18.1 mm Hg. All patients demonstrated normal sleep parameters. Oxygen saturation further declined in 5 patients during sleep. However, no associated alteration in respiratory parameters was observed and no significant arrhythmia. The mean AHI was 1.1±1.0/h. No subject met the pre-defined criterion for sleep apnea.
Conclusion: Although further oxygen desaturation may be observed during sleep in patients with CCHD, it occurs in the absence of sleep disordered breathing.
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Differences between nighttime REM and NREM dreams are well-established but only rarely are daytime REM and NREM nap dreams compared with each other or with daydreams. Fifty-one participants took daytime naps (with REM or NREM awakenings)... more
Differences between nighttime REM and NREM dreams are well-established but only rarely are daytime REM and NREM nap dreams compared with each other or with daydreams. Fifty-one participants took daytime naps (with REM or NREM awakenings) and provided both waking daydream and nap dream reports. They also provided ratings of their bizarreness, sensory experience, and emotion intensity. Recall rates for REM (96%) and NREM (89%) naps were elevated compared to typical recall rates for nighttime dreams (80% and 43% respectively), suggesting an enhanced circadian influence. All attribute ratings were higher for REM than for NREM dreams, replicating findings for nighttime dreams. Compared with daydreams, NREM dreams had lower ratings for emotional intensity and sensory experience while REM dreams had higher ratings for bizarreness and sensory experience. Results support using daytime naps in dream research and suggest that there occurs selective enhancement and inhibition of specific dream attributes by REM, NREM and waking state mechanisms.
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Previous work demonstrates that memories about a target experience are incorporated into dream content according to a U-shaped temporal pattern with a peak of incorporations around 1-2 days following the experience (day-residue effect), a... more
Previous work demonstrates that memories about a target experience are incorporated into dream content according to a U-shaped temporal pattern with a peak of incorporations around 1-2 days following the experience (day-residue effect), a diminution on days 3-4, and a recurrence of incorporations on days 5-7 (dream-lag effect). This temporal pattern has been observed for many types of experiences, but no study has yet investigated either whether the pattern occurs differentially for qualitatively distinct, yet temporally proximal, experiences or whether the pattern also manifests in generic changes that are not specifically related to the target memory. The current study traced memory source incorporation patterns of two qualitatively distinct but temporally overlapping events: a laboratory overnight stay (LAB), considered to be an interpersonal and passive experience; and a virtual reality maze task (VR), considered to be a solitary and active experience. Hypotheses were that: 1) elements of LAB and VR experiences would be incorporated independently and exhibit different temporal patterns of incorporation into dream content; and 2) these incorporation patterns would be associated with different generic changes in dream content, i.e., a primarily external dreamed Locus of Control (Dream LoC) for dreams incorporating LAB experiences and a primarily internal Dream LoC for dreams incorporating VR experiences. Twenty-six participants each spent 1 night in the sleep laboratory, underwent a VR maze task in the morning, and then kept a home dream log for 10 days. Judges rated dreams for evidence of incorporation of LAB and VR experiences. Results were consistent with expectations: 1) LAB and VR experiences showed independent and opposite temporal incorporation patterns; LAB incorporations showed both day-residue and dream-lag effects whereas VR incorporations revealed a peak only on day 4; 2) Dream LoC scores were more external for Day 1 (peak of LAB incorporations), and more internal for Day 4 (peak of VR incorporations). Different incorporation patterns for these two experiences may reflect separate underlying processes of memory consolidation responding to different types of stimulus events. Further, temporal patterning of both specific dream incorporations and general dream content changes (LoC) may reflect qualitatively different aspects of episodic memory consolidation.
Research Interests: Neuroscience, Psychology, Cognitive Psychology, Social Psychology, Memory (Cognitive Psychology), and 14 moreLearning & Memory, Affective Neuroscience, Social Neuroscience, Neurobiology of Learning and Memory, Memory Studies, Dreams (Psychology), Cognitive Neuroscience, Dreams, Neurobiology, Sleep & Circadian Rhythms, Lucid Dreaming, Memory, Sleep and Dreaming, and Sleep
Study Objectives: The goals of the study were to assess semantic priming to emotion and nonemotion cue words using a novel measure of associational breadth for participants who either took rapid eye movement (REM) or nonrapid eye movement... more
Study Objectives: The goals of the study were to assess semantic priming to emotion and nonemotion cue words using a novel measure of associational breadth for participants who either took rapid eye movement (REM) or nonrapid eye movement (NREM) naps or who remained awake, and to assess the relation of priming to REM sleep consolidation and REM sleep inertia effects.
Design: The associational breadth task was applied in both a priming condition, where cue words were signaled to be memorized prior to sleep (primed), and a nonpriming condition, where cue words were not memorized (nonprimed). Cue words were either emotional (positive, negative) or nonemotional. Participants were randomly assigned to either an awake (WAKE) or a sleep condition, which was subsequently split into NREM or REM groups depending on stage at awakening.
Setting: Hospital-based sleep laboratory.
Participants: Fifty-eight healthy participants (22 male) ages 18 to 35 y (mean age = 23.3 ± 4.08 y).
Measurements and Results: The REM group scored higher than the NREM or WAKE groups on primed, but not nonprimed emotional cue words; the effect was stronger for positive than for negative cue words. However, REM time and percent correlated negatively with degree of emotional priming. Priming occurred for REM awakenings but not for NREM awakenings, even when the latter sleep episodes contained some REM sleep.
Conclusions: Associational breadth may be selectively consolidated during REM sleep for stimuli that have been tagged as important for future memory retrieval. That priming decreased with REM time and was higher only for REM sleep awakenings is consistent with two explanatory REM sleep processes: REM sleep consolidation serving emotional downregulation and REM sleep inertia.
Design: The associational breadth task was applied in both a priming condition, where cue words were signaled to be memorized prior to sleep (primed), and a nonpriming condition, where cue words were not memorized (nonprimed). Cue words were either emotional (positive, negative) or nonemotional. Participants were randomly assigned to either an awake (WAKE) or a sleep condition, which was subsequently split into NREM or REM groups depending on stage at awakening.
Setting: Hospital-based sleep laboratory.
Participants: Fifty-eight healthy participants (22 male) ages 18 to 35 y (mean age = 23.3 ± 4.08 y).
Measurements and Results: The REM group scored higher than the NREM or WAKE groups on primed, but not nonprimed emotional cue words; the effect was stronger for positive than for negative cue words. However, REM time and percent correlated negatively with degree of emotional priming. Priming occurred for REM awakenings but not for NREM awakenings, even when the latter sleep episodes contained some REM sleep.
Conclusions: Associational breadth may be selectively consolidated during REM sleep for stimuli that have been tagged as important for future memory retrieval. That priming decreased with REM time and was higher only for REM sleep awakenings is consistent with two explanatory REM sleep processes: REM sleep consolidation serving emotional downregulation and REM sleep inertia.
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Research Interests: Sleep Physiology, Cognition, Altered States of Consciousness, Clinical Neuroscience, Sleep Medicine, and 17 moreCognitive Neuroscience, Adolescent, Dreams, Sleep & Circadian Rhythms, Biological Sciences, Dreaming, Humans, Sleep and Dreaming, Sleep Deprivation, Female, Male, Sleep, Sleep deprivation effects, REM & non-REM Sleep, Hypnagogic Imagery, Adult, and Rem Sleep
Felt presence, a sensation that “someone is there”, is an integral part of our everyday experience. It can manifest itself in a variety of forms ranging from most subtle fleeting impressions to intense hallucinations of demonic assault or... more
Felt presence, a sensation that “someone is there”, is an integral part of our everyday experience. It can manifest itself in a variety of forms ranging from most subtle fleeting impressions to intense hallucinations of demonic assault or visions of the divine. Felt presence phenomenon outside of the context of neurological disorders is largely neglected and not well understood by contemporary science. This paper focuses on the experiential and expressive qualities of the phenomenon and attempts to bring forth the complexity and the richness of possibilities for inter- and intrasubjective awareness represented by these experiences. Are these simply misperceptions and hallucinations heightened and enforced by the mystical or superstitious mind? Or are these entities projections of our own “selves”, elements of self-estrangement? How are such experiences shaping our understanding of ourselves and of others? And finally, what is the interplay between intersubjective, private experiences and private or public spaces of dwelling?
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In the early 1900s, the Dream of the Rarebit Fiend comic strip conveyed how the spicy cheese dish Welsh rarebit leads to bizarre and disturbing dreams. Today, the perception that foods disturb dreaming persists. But apart from case... more
In the early 1900s, the Dream of the Rarebit Fiend comic strip conveyed how the spicy cheese dish Welsh rarebit leads to bizarre and disturbing dreams. Today, the perception that foods disturb dreaming persists. But apart from case studies, some exploratory surveys, and a few lab studies on how hunger affects dreaming, there is little empirical evidence addressing this topic. The present study examines three aspects of the food/dreaming relationship; it attempts to: (1) assess the prevalence of the perception of food-dependent dreaming and the types of foods most commonly blamed; (2) determine if perceived food-dependent dreaming is associated with dietary, sleep or motivational factors; and (3) explore whether these factors, independent of food/dreaming perceptions, are associated with reports of vivid and disturbing dreams. Three hundred and ninety six students completed questionnaires evaluating sleep, dreams, and dietary habits and motivations. Items queried whether they had noticed if foods produced bizarre or disturbing dreams and if eating late at night influenced their dreams. The perception of food-dependent dreaming had a prevalence of 17.8%; with dairy products being the most frequently blamed food category (39–44%). Those who perceived food-dependent dreaming differed from others by reporting more frequent and disturbing dreams, poorer sleep, higher coffee intake, and lower Intuitive Eating Scale scores. Reports of disturbing dreams were associated with a pathological constellation of measures that includes poorer sleep, binge-eating, and eating for emotional reasons. Reports of vivid dreams were associated with measures indicative of wellness: better sleep, a healthier diet, and longer times between meals (fasting). Results clarify the relationship between food and dreaming and suggest four explanations for the perception of food-dependent dreaming: (1) food specific effects; (2) food-induced distress; (3) folklore influences, and (4) causal misattributions. Research and clinical implications are discussed.
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Memory consolidation is associated with sleep physiology but the contribution of specific sleep stages remains controversial. To clarify the contribution of REM sleep, participants were administered two REM sleep-sensitive tasks to... more
Memory consolidation is associated with sleep physiology but the contribution of specific sleep stages remains controversial. To clarify the contribution of REM sleep, participants were administered two REM sleep-sensitive tasks to determine if associated changes occurred only in REM sleep. Twenty-two participants (7 men) were administered the Corsi Block Tapping and Tower of Hanoi tasks prior to and again after a night of sleep. Task improvers and non-improvers were compared for sleep structure, sleep spindles, and dream recall. Control participants (N = 15) completed the tasks twice during the day without intervening sleep. Overnight Corsi Block improvement was associated with more REM sleep whereas Tower of Hanoi improvement was associated with more N2 sleep. Corsi Block improvement correlated positively with %REM sleep and Tower of Hanoi improvement with %N2 sleep. Post-hoc analyses suggest Tower of Hanoi effects—but not Corsi Block effects—are due to trait differences. Sleep spindle density was associated with Tower of Hanoi improvement whereas spindle amplitude correlated with Corsi Block improvement. Number of REM awakenings for dream reporting (but not dream recall per se) was associated with Corsi Block, but not Tower of Hanoi, improvement but was confounded with REM sleep time. This non-replication of one of 2 REM-sensitive task effects challenges both ‘dual-process’ and ‘sequential’ or ‘sleep organization’ models of sleep-dependent learning and points rather to capacity limitations on REM sleep. Experimental awakenings for sampling dream mentation may not perturb sleep-dependent learning effects; they may even enhance them.
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The widespread use of standard polysomnographic (PSG) criteria for identifying sleep stages (Rechtschaffen and Kales 1968) has helped promote an artificially categorical view of sleep and the unproven notion that sleep stages are mutually... more
The widespread use of standard polysomnographic (PSG) criteria for identifying sleep stages (Rechtschaffen and Kales 1968) has helped promote an artificially categorical view of sleep and the unproven notion that sleep stages are mutually exclusive states separated by abrupt transitions. Rather, evidence suggests that sleep stages consist of fluid, dissociable clusters of processes, with overlaps and admixtures being common under various circumstances (Nielsen 2000b; Himanen and Hasan 2000). This emerging, alternative view of sleep has important ramifications for theories of dreaming—and thus for theories of dream function like the protoconsciousness (ProtoCs) theory.
Research Interests: Cognitive Psychology, Cognitive Neuropsychology, Dreams (Psychology), Cognitive Neuroscience, Dreams, and 9 moreSleep & Circadian Rhythms, Sleep and Dreaming, Sleep, Psychology of Sleep and Dreaming, REM & non-REM Sleep, REM sleep and Memory consolidation, Rem Sleep, REM Sleep Deprivation and Dreams, and Dreams, Consciousness Studies, Qualitative Research
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... more
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.
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Research Interests: Emotion, Emotional intelligence, Emotion Regulation, Sleep Medicine, Emotional Intelligence (Psychology), and 10 moreDreams (Psychology), Dreams, Sleep & Circadian Rhythms, Alexithymia, Sleep and Dreaming, Nightmares, Sleep disorders, Psychology of Sleep and Dreaming, Psychological distress, and Parasomnia
Dreams are thought to respond to self- and socially-relevant situations that evoke strong emotions and require rapid adaptation. First pregnancy is such a situation during which maternal mental representations (MMR) of the unborn baby,... more
Dreams are thought to respond to self- and socially-relevant situations that evoke strong emotions and require rapid adaptation. First pregnancy is such a situation during which maternal mental representations (MMR) of the unborn baby, the self and significant others undergo remodeling. Some studies suggest that dreams during pregnancy contain more MMR and are more dysphoric, but such studies contain important methodological flaws. We assessed whether dreamed MMR, like waking MMR, change from the 7th month of pregnancy to birth, and whether pregnancy–related themes and non-pregnancy characteristics are also transformed. Sixty non-pregnant and 59 pregnant women (37 early and 22 late 3rd trimester) completed demographic and psychological questionnaires and 14-day home dream logs. Dream reports were blindly rated according to four dream categories: (1) Dreamed MMR, (2) Quality of baby/child representations, (3) Pregnancy-related themes, (4) Non-pregnancy characteristics. Controlling for age, relationship and employment status, education level and state anxiety, women in both pregnant groups reported more dreams depicting themselves as a mother or with babies/children than did non-pregnant women (all p = 0.006). Baby/child representations were less specific in the late 3rd than in the early 3rd trimester (p = 0.005) and than in non-pregnant women (p = 0.01). Pregnant groups also had more pregnancy, childbirth and fetus themes (all p = 0.01). Childbirth content was higher in late than in early 3rd trimester (p = 0.01). Pregnant groups had more morbid elements than did the non-pregnant group (all p < 0.05). Dreaming during pregnancy appears to reflect daytime processes of remodeling MMR of the woman as a mother and of her unborn baby, and parallels a decline in the quality of baby/child representations in the last stage of pregnancy. More frequent morbid content in late pregnancy suggests that the psychological challenges of pregnancy are reflected in a generally more dysphoric emotional tone in dream content.
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We previously reported that college students who indicated engaging in frequent dreamenacting behaviors also scored high on a new measure of mirror behaviors, which is the propensity to imitate another person’s emotions or actions. Since... more
We previously reported that college students who indicated engaging in frequent dreamenacting behaviors also scored high on a new measure of mirror behaviors, which is the propensity to imitate another person’s emotions or actions. Since dream-enacting behaviors are frequently the culmination of nightmares, one explanation for the observed relationship is that individuals who frequently display mirror behaviors are also prone to nightmares. We used the Mirror Behavior Questionnaire (MBQ) and self-reported frequencies of nightmares to assess this possibility.
A sample of 480 students, consisting of 188 males (19.2 ± 1.73 years) and 292 females (19.0 ± 1.55 years) enrolled in a first-year university psychology course, participated for course credit. They completed a battery of questionnaires that included the 16-item MBQ, plus an item about nightmare frequency (NMF) in the past 30 days. NMF scores were split to create low, medium, and high NMF groups.
MBQ total scores were significantly higher for female than for male subjects, but an interaction revealed that this was true only for Hi-NMF subjects. MBQ Factor 4, Motor Skill Imitation, paralleled this global interaction for females, whereas MBQ Factor 3, Sleepiness/Anger Contagion, was elevated only for Hi-NMF males. Item analyses indicated that Hi- and Med-NMF females scored higher than Lo-NMF females on the 3 items of Factor 4 that reflect voluntary imitation (imitating famous/cartoon voices, being a physically active spectator, and learning new skills by observing), as well as on 2 other items that reflect involuntary imitation (contagious yawning and self-rated empathy). Although Hi- and Lo-NMF males differed most clearly on the sleepiness item of Factor 3, all 3 items on this factor (including anger contagion and contagious yawning) are plausibly associated with perception of and response to social threat.
Results provide evidence that among females nightmares are ssociated with voluntary and involuntary mirror behaviors during wakefulness, while among males nightmares are associated with threat-related mirror behaviors during wakefulness. They thus support the possibility that the association between mirror behaviors and dream-enacting behaviors is due to a common mirror neuron mechanism that underlies mirror behaviors and nightmares and that involves motor, rather than emotional, resonance. These results have implications for understanding the comorbidity of nightmares and other pathological symptoms such as imitative suicidal behaviors, the influence of observational learning on dissociative symptomatology, and the predominance of threat and aggression in the dream enacting behaviors of REM sleep behavior disorder.
A sample of 480 students, consisting of 188 males (19.2 ± 1.73 years) and 292 females (19.0 ± 1.55 years) enrolled in a first-year university psychology course, participated for course credit. They completed a battery of questionnaires that included the 16-item MBQ, plus an item about nightmare frequency (NMF) in the past 30 days. NMF scores were split to create low, medium, and high NMF groups.
MBQ total scores were significantly higher for female than for male subjects, but an interaction revealed that this was true only for Hi-NMF subjects. MBQ Factor 4, Motor Skill Imitation, paralleled this global interaction for females, whereas MBQ Factor 3, Sleepiness/Anger Contagion, was elevated only for Hi-NMF males. Item analyses indicated that Hi- and Med-NMF females scored higher than Lo-NMF females on the 3 items of Factor 4 that reflect voluntary imitation (imitating famous/cartoon voices, being a physically active spectator, and learning new skills by observing), as well as on 2 other items that reflect involuntary imitation (contagious yawning and self-rated empathy). Although Hi- and Lo-NMF males differed most clearly on the sleepiness item of Factor 3, all 3 items on this factor (including anger contagion and contagious yawning) are plausibly associated with perception of and response to social threat.
Results provide evidence that among females nightmares are ssociated with voluntary and involuntary mirror behaviors during wakefulness, while among males nightmares are associated with threat-related mirror behaviors during wakefulness. They thus support the possibility that the association between mirror behaviors and dream-enacting behaviors is due to a common mirror neuron mechanism that underlies mirror behaviors and nightmares and that involves motor, rather than emotional, resonance. These results have implications for understanding the comorbidity of nightmares and other pathological symptoms such as imitative suicidal behaviors, the influence of observational learning on dissociative symptomatology, and the predominance of threat and aggression in the dream enacting behaviors of REM sleep behavior disorder.
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Dream-enacting behaviors (DEBs) are behavioral expressions of forceful dream images often occurring during sleep-to-wakefulness transitions. We propose that DEBs reflect brain activity underlying social cognition, in particular,... more
Dream-enacting behaviors (DEBs) are behavioral expressions of forceful dream images often occurring during sleep-to-wakefulness transitions. We propose that DEBs reflect brain activity underlying social cognition, in particular, motor-affective resonance generated by the mirror neuron system. We developed a Mirror Behavior Questionnaire (MBQ) to assess some dimensions of mirror behaviors and investigated relationships between MBQ scores and DEBs in a large of university undergraduate cohort. MBQ scores were normally distributed and described by a four-factor structure (Empathy/Emotional Contagion, Behavioral Imitation, Sleepiness/Anger Contagion, Motor Skill Imitation). DEB scores correlated positively with MBQ total and factor scores even with social desirability, somnambulism and somniloquy controlled. Emotion-specific DEB items correlated with corresponding emotion-specific MBQ items, especially crying and smiling. Results provide preliminary evidence for cross-state relationships between propensities for dream-enacting and mirror behaviors—especially behaviors involving motor-affective resonance—and our suggestion that motor-affective resonance mediates dream-enactment imagery during sleep and emotional empathy during waking.
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We assessed dream recall frequency (DRF) and dream theme diversity (DTD) with an internet questionnaire among a cohort of 28,888 male and female participants aged 10–79 years in a cross-sectional design. DRF increased from adolescence... more
We assessed dream recall frequency (DRF) and dream theme diversity (DTD) with an internet questionnaire among a cohort of 28,888 male and female participants aged 10–79 years in a cross-sectional design. DRF increased from adolescence (ages 10–19) to early adulthood (20–29) and then decreased again for the next 20 years. The nature of this decrease differed for males and females. For males, it began earlier (30–39), proceeded more gradually, and reached a nadir earlier (40–49) than it did for females. For females, it began later (40–49), dropped more abruptly, and reached nadir later (50–59). Marked sex differences were observed for age strata 10–19 through 40–49 and year-by-year analyses estimated the window for these differences to be more precisely from 14 to 44 years. DTD decreased linearly with age for both sexes up to 50–59 and then dropped even more sharply for 60–79. There was a sex difference favoring males on this measure but only for ages 10–19. Findings replicate, in a single sample, those from several previous studies showing an increase in DRF from adolescence to early adulthood, a subsequent decrease primarily in early and middle adulthood, and different patterns of age-related decrease in the two sexes. Age-related changes in sleep structure, such as decreasing %REM sleep which parallel the observed dream recall changes, might help explain these findings, but these sleep changes are much smaller and more gradual in nature. Changes in the phase and amplitude of circadian rhythms of REM propensity and generational differences in life experiences may also account for some part of the findings. That decreases in DTD parallel known age-related decreases in episodic and autobiographical memory may signify that this new diversity measure indexes an aspect of autobiographical memory that also influences dream recall.
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Felt presence, a sensation that ‘‘someone is there’’, is an integral part of our everyday experience. It can manifest itself in a variety of forms ranging from most subtle fleeting impressions to intense hallucinations of demonic assault... more
Felt presence, a sensation that ‘‘someone is there’’, is an integral part of our everyday experience. It can manifest itself in a variety of forms ranging from most subtle fleeting impressions to intense hallucinations of demonic assault or visions of the divine. Felt presence phenomenon outside of the context of neurological disorders is largely neglected and not well understood by contemporary science. This paper focuses on the experiential and expressive qualities of the phenomenon and attempts to bring forth the complexity and the richness of possibilities
for inter- and intrasubjective awareness represented by these experiences. Are these simply misperceptions and hallucinations heightened and enforced by the mystical or superstitious mind? Or are these entities projections of our own ‘‘selves’’, elements of self-estrangement? How are such experiences shaping our understanding of ourselves and of others? And finally, what is the interplay between intersubjective, private experiences and private or public spaces of dwelling?
for inter- and intrasubjective awareness represented by these experiences. Are these simply misperceptions and hallucinations heightened and enforced by the mystical or superstitious mind? Or are these entities projections of our own ‘‘selves’’, elements of self-estrangement? How are such experiences shaping our understanding of ourselves and of others? And finally, what is the interplay between intersubjective, private experiences and private or public spaces of dwelling?
Research Interests: Cognitive Psychology, Sleep Physiology, Phenomenology, Spirituality & Mysticism, Sleep Medicine, and 16 morePhenomenology of the body, Sleep Paralysis, Spirituality & Psychology, Dreams (Psychology), Cognitive Neuroscience, Dreams, Phenomenology of Space and Place, Sleep & Circadian Rhythms, Parapsychology, Anthropology, Mediumship, Phenomenology, Spiritualism, Paranormal, Supernatural, Folklore, Religion, Sociology, Anthropology of Dreams and Dreaming, Sleep and Dreaming, Other, Sleep, Numinous Experience, Notion of Numinousity, and Dreams, Consciousness Studies, Qualitative Research
Nightmares and other common disturbances of dreaming involve a perturbation of emotional expression during sleep. Nightmares, the most prevalent dream disturbance, are now recognized as comprising several dysphoric emotions, including... more
Nightmares and other common disturbances of dreaming involve a perturbation of emotional expression during sleep. Nightmares, the most prevalent dream disturbance, are now recognized as comprising several dysphoric emotions, including especially fear, although some argue that existential (or grief) dreams should be considered a separate entity. A genetic basis for nightmares has been demonstrated and their pathophysiology involves a surprising underactivation of the sympathetic nervous system in many instances. Personality factors, such as nightmare chronicity and distress and coping styles are mediating determinants of their clinical severity, as are drug and alcohol use. Many treatments have been described, with much support for the effectiveness of shortterm cognitive and behavior interventions such as systematic desensitization and imagery rehearsal. Several related dream disturbances occur at the transitions into or out of sleep and involve dysphoric emotions ranging from malaise to fear to frank terror. These disturbances include sleep starts, terrifying hypnagogic hallucinations, sleep paralysis, somniloquy with dream content, false awakenings, and disturbed lucid dreaming. The distinctive nature of these disturbances may be mediated by immediately preceding waking state processes (e.g., consciousness, sensory vividness) that intrude upon or carry over into dreaming.
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The task of differentiating dreaming from other forms of imaginative cognition and of classifying different dream types and subtypes is largely incomplete. However, a growing interest in dreaming’s capacity for simulating waking reality... more
The task of differentiating dreaming from other forms of imaginative cognition and of classifying different dream types and subtypes is largely incomplete. However, a growing interest in dreaming’s capacity for simulating waking reality experience offers a viable point of departure for furthering this unfinished task. Most types of dream content measures (e.g., prevalence, frequency, intensity, structural coherence) are predicated, directly or indirectly, on this assumption about dreaming’s capacity for simulating reality and provide converging support for the reality-simulation assumption. Even measures of dream bizarreness—which is quite common in dreams—may be understood as attempts to quantify failures of the simulation mechanism. Both simulated content and bizarreness measures may be viable approaches for completing the task of dream classification. However, a third level of analysis also related to reality simulation may prove key in this enterprise. This is the simulation of the subtle, perception like nature of waking experience, namely, the process of seeking out and picking up apparent information, not the appreciation of the contents of this process. This level of subjective experience is only difficultly accessed by awaking, selfreflective subjects, so its study in dream experience may require greater use of targeted probe questions and less conventional methods such as selecting subjects for their communication abilities and training them in self-observation.
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Disturbed dreaming has been identified as a primary or secondary symptom in many medical conditions. The quality of such dreaming can be conveniently classified as varying along a continuum of subjective intensity. At one extreme, dream... more
Disturbed dreaming has been identified as a primary or secondary symptom in many medical conditions. The quality of such dreaming can be conveniently classified as varying along a continuum of subjective intensity. At one extreme, dream recall ceases entirely (global cessation of dreaming) or is unusually impoverished in quantity or content (dream impoverishment). Impoverishment affects patients with alexithymia, posttraumatic stress disorder (PTSD), and some brain syndromes. At the other extreme, dreaming is profuse and vivid (excessive dreaming), affecting patients with epic dreaming, some brain lesions, and withdrawal from some medications, or it becomes so intense that it is confused with reality (dream–reality confusion) as is the case with bereavement or the postpartum state, intensive care unit (ICU) delirium, limbic lobe damage, and psychotic states. Intense dreaming may become rigidly repetitive (repetitive dream content). Conditions such as rapid eye movement (REM) sleep behavior disorder with or without parkinsonism, epilepsy, PTSD, migraine, and cardiac illness are affected by dream repetition. The intensity dimension of dream disturbance appears to mirror various aberrations of dreaming’s normal capacity to simulate reality. Accordingly, episodic memories, which are normally absent from dream content, appear more frequently in disturbed dreams. Although effective treatments are available
for several common dream disturbances, the development of new treatments might benefit from attention to intensified reality simulation and the role of episodic memory activation.
for several common dream disturbances, the development of new treatments might benefit from attention to intensified reality simulation and the role of episodic memory activation.
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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... more
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.
Research Interests: Clinical Psychology, Personality Psychology, Emotion, Sex and Gender, Emotional intelligence, and 20 morePersonality, Social Cognition, Personality Assessment, Personality Disorders, Theories Of Personality, Affective Neuroscience, Sleep Medicine, Imagination, Cognitive Neuroscience, Sleep & Circadian Rhythms, Alexithymia, Social Cognitive Affective Neuroscience, Dreaming, Clinical research, Sleep and Dreaming, Nightmares, Sleep disorders, Sleep, Gender Differences, and Laterality, Sex Differences, Cognitive Abilities and Spatial Bilities
Dreaming is influenced by many of the same types of chronobiologic and sleep-dependent factors that regulate sleep processes. These principally include the 90-minute REM–NREM ultradian rhythm, the 24-hour circadian rhythm, and the... more
Dreaming is influenced by many of the same types of chronobiologic and sleep-dependent factors that regulate sleep processes. These principally include the 90-minute REM–NREM
ultradian rhythm, the 24-hour circadian rhythm, and the sleep-dependent increase in REM propensity. Different features of dreaming have been associated with these factors, such as the probability of recalling dream content, the length of dream reports, and the visual intensity of the dream experience. The interactions between ultradian, circadian, and sleep-dependent factors may provide a more complete portrait of chronobiologic influences on dream production.
ultradian rhythm, the 24-hour circadian rhythm, and the sleep-dependent increase in REM propensity. Different features of dreaming have been associated with these factors, such as the probability of recalling dream content, the length of dream reports, and the visual intensity of the dream experience. The interactions between ultradian, circadian, and sleep-dependent factors may provide a more complete portrait of chronobiologic influences on dream production.
Research Interests: Chronobiology, Neuroscience, Human Physiology, Cognitive Psychology, Cognitive Science, and 13 moreSleep Physiology, Brain and Cognitive Development, Sleep Medicine, Dreams (Psychology), Cognitive Neuroscience, Dreams, Sleep & Circadian Rhythms, EPILEPSY, SLEEP DISORDERS AND COGNITIVE NEUROLOGY, Sleep and Dreaming, Sleep disorders, Sleep, Biorhythms, and Chronobiology, Sleep Regulation
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Summary A review of the scientific literature clarifies several chronobiological features of dreaming. The literature supports the conclusions that dreaming ‘intensity’ and, to a lesser extent dream-like quality, is modulated by (1) a... more
Summary A review of the scientific literature clarifies several chronobiological features of dreaming. The literature supports the conclusions that dreaming ‘intensity’ and, to a lesser extent dream-like quality, is modulated by (1) a sinusoidal, 90-min ultradian oscillation, (2) a ‘switch-like’ circadian oscillation,
(3) a 12-h circasemidian rhythm, and (4) a 28-day circatrigintan rhythm (for women). Further, access to dream memory sources appears to be modulated by (5) a 7-day circaseptan rhythm. Further study of these rhythmic influences on dreaming may
help to explain diverse and often contradictory findings in the dream research literature, to clarify relationships between dreaming and waking cognitive processes, to explain relationships between disturbed phase relationships and
dream disturbances and to shed new light on the problems of dreaming’s functions and biological markers. Further chronobiological studies of dreaming will likely enable the development of theoretical models that explain how interactions
between and within major levels of oscillation determine the variable characteristics of dreaming.
(3) a 12-h circasemidian rhythm, and (4) a 28-day circatrigintan rhythm (for women). Further, access to dream memory sources appears to be modulated by (5) a 7-day circaseptan rhythm. Further study of these rhythmic influences on dreaming may
help to explain diverse and often contradictory findings in the dream research literature, to clarify relationships between dreaming and waking cognitive processes, to explain relationships between disturbed phase relationships and
dream disturbances and to shed new light on the problems of dreaming’s functions and biological markers. Further chronobiological studies of dreaming will likely enable the development of theoretical models that explain how interactions
between and within major levels of oscillation determine the variable characteristics of dreaming.
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Research Interests:
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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... more
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.
Research Interests: Clinical Psychology, Developmental Psychology, Psychotherapy, Art Therapy, Psychotherapy and Counseling, and 11 moreExpressive Arts Therapy, Creative Arts Therapy, Dreams (Psychology), Dreams, Sleep & Circadian Rhythms, EPILEPSY, SLEEP DISORDERS AND COGNITIVE NEUROLOGY, Nightmares, Sleep disorders, Cognitive Behavioral Treatment Method, Parasomnias, and Relaxation; Imagery; Rehabilitation
Research Interests: Mirror Neurons, Consciousness, Social Neuroscience, The Other, Sleep Paralysis, and 12 moreImagery (Cognitive Psychology), Delusions, Dreaming, Mirror neurons and Intersubjectivity, Hallucinations, Imaginary companions, Imagined Interactions, Mirror Neurons and Culture, Sense of Presence, Mirror Neurones and empathy, Phantom Limbs and Mirror Therapy, and Social Imagery and Collective Memory
Research Interests: Neuroscience, Cognitive Psychology, Cognitive Science, Memory (Cognitive Psychology), The Self of Groups, and 14 moreConsciousness (Psychology), Sleep Physiology, Cognition, Consciousness, Self Observation, Memory Studies, Introspection, Cognitive Neuroscience, Dreams, Sleep & Circadian Rhythms, Systematic Reviews, Dreaming, Sleep and Dreaming, and Hippocamus
Research Interests: Sleep Physiology, Human Pregnancy, Birth And Breastfeeding, Dreams (Psychology), Dreams, Sleep & Circadian Rhythms, and 9 morePsychology of Pregnancy, Anthropology/Sociology of Pregnancy, Dreaming, Pregnancy, Sleep and Dreaming, Postpartum Depression, Sleep disorders, Nightmare, and Postpartum Management and Experiences
This chapter introduces the notion of 'oneirogenesis' or the origin of daytime beliefs in dream experiences. Dreams with an exceptionally vivid sensation of reality ('reality dreams')--of which there are many types (e.g., nightmares,... more
This chapter introduces the notion of 'oneirogenesis' or the origin of daytime beliefs in dream experiences. Dreams with an exceptionally vivid sensation of reality ('reality dreams')--of which there are many types (e.g., nightmares, lucid dreams, flying dreams, sex dreams)--are particularly likely to engender and modify waking beliefs. Moreover, animistic beliefs (e.g., that the soul exists independent of the body) and other beliefs in spiritual entities and events are especially likely to be influenced by such dreams. Examples are provided from both the historical literature and laboratory studies.
Research Interests: Religion, New Religious Movements, Comparative Religion, Sleep Physiology, Psychology of Religion, and 13 moreDemonology, Religious Conversion, Dreams (History), Visions And Dreams, Sleep Paralysis, Contemporary animism, Religious Experience, Dreams, Animism, Lucid Dreaming, Philosophy of dream, Hallucinations, and Dream Psychology
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The published literature suggests that systematic self- observation may be a suitable method for clarifying the nature and correlates of hypnagogic imagery and thus a useful adjunct to psychophysiological and cognitive studies of sleep... more
The published literature suggests that systematic self- observation may be a suitable method for clarifying the nature and correlates of hypnagogic imagery and thus a useful adjunct to psychophysiological and cognitive studies of sleep onset. The potential applicability of one recently proposed self-observation procedure (Nielsen, 1992) to such studies is demonstrated in the present work. The procedure permits numerous hypnagogic images to be collected during spontaneous drowsy periods occurring during the day. The observer sits in an upright, head-unsupported position, fixes an observational intent, and pays attention to internal events; images are observed, transcribed and then assessed for their likely memory sources. The procedure has been pilot-tested by the author in four exploratory studies comprising over 250 hypnagogic images. Neuromuscular events accompanying these images (e.g., head nods, leg jerks) and EEG correlates of the images are described. Certain distinctions among imagery types are suggested, e.g., fleeting vs. fully-formed, images with self movement vs. images with non-self movement. Silberer's conclusions regarding the 'autosymbolic' function of hypnagogic images are supported and extended by the results. Four types of memory element (immediate, short-, medium-, and long-term) appear to have contributed causally to the formation of these hypnagogic images and are illustrated. To demonstrate how the self- observational method may be used to model the formation of hypnagogic imagery from such memory sources, a single sample image and its multiple memory sources are described and analyzed in detail.
Research Interests: Psychoanalysis, Memory (Cognitive Psychology), Sleep Physiology, Altered States of Consciousness, Working Memory, and 13 moreConsciousness, Introspection, Imagery (Psychology), Cognitive Neuroscience, Imagery (Cognitive Psychology), Dreams, Sleep & Circadian Rhythms, Consciousness Studies, Dreaming, Mental Imagery, Sleep and Dreaming, Sleep Onset, and Hypnagogic Imagery
Relations between common nightmares and chronobiological factors remain poorly understood. The possibility that nightmare frequency and distress are associated with chronotype (“morningness-eveningness”) was investigated in a sample of... more
Relations between common nightmares and chronobiological factors remain poorly understood. The possibility that nightmare frequency and distress are associated with chronotype (“morningness-eveningness”) was investigated in a sample of respondents to an Internet questionnaire. Over a 4½-year period, a total of 3978 subjects (mean age = 26.5 ± 11.6 yrs; age range = 10-69; 2933 female, 1045 male) submitted responses to single items about chronotype and nightmares as well as to other demographic variables. Analyses of chronotype and nightmares items by age and gender replicated most previous findings
for these measures—validating their further assessment—and uncovered abrupt increases in nightmare distress between ages 10-19 and 20-29 for females and ages 30-39 and 40-49 for males. Most important, there was a strong association
between nightmares and eveningness for female subjects. The latter was expressed as a linear association between nightmare frequency and increasing eveningness and a cubic association between nightmare distress and increasing eveningness; the definite evening types displayed the most severe nightmares.
The effect for nightmare frequency was independent of age and sleep duration but was eliminated when nightmare distress was covaried. For females, the nightmare/eveningness association appeared at ages 20 to 29 for the definite evening type and only later, at ages 30 to 39, for the moderate evening type. Findings are consistent with the possibility that nightmares are the expression of a more general pathological factor that is characteristic of eveningness and that is responsible for affective symptoms such as neuroticism and depression. This pathological factor appears to be expressed in late adolescence/
early adulthood, and relative morningness may be a protective factor delaying its onset. The well-established circadian modulations of cognitive, social, and affective tasks that are influenced by chronotype may extend to the memory and affective processes of sleep—including dreaming. This chronotypic influence, together with a likely gender difference in the neurophysiological substrate of emotional processing, may result in the differential occurrence of nightmares for female evening types.
for these measures—validating their further assessment—and uncovered abrupt increases in nightmare distress between ages 10-19 and 20-29 for females and ages 30-39 and 40-49 for males. Most important, there was a strong association
between nightmares and eveningness for female subjects. The latter was expressed as a linear association between nightmare frequency and increasing eveningness and a cubic association between nightmare distress and increasing eveningness; the definite evening types displayed the most severe nightmares.
The effect for nightmare frequency was independent of age and sleep duration but was eliminated when nightmare distress was covaried. For females, the nightmare/eveningness association appeared at ages 20 to 29 for the definite evening type and only later, at ages 30 to 39, for the moderate evening type. Findings are consistent with the possibility that nightmares are the expression of a more general pathological factor that is characteristic of eveningness and that is responsible for affective symptoms such as neuroticism and depression. This pathological factor appears to be expressed in late adolescence/
early adulthood, and relative morningness may be a protective factor delaying its onset. The well-established circadian modulations of cognitive, social, and affective tasks that are influenced by chronotype may extend to the memory and affective processes of sleep—including dreaming. This chronotypic influence, together with a likely gender difference in the neurophysiological substrate of emotional processing, may result in the differential occurrence of nightmares for female evening types.
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Background: Sleep disordered breathing is frequently observed in patients with cardiovascular disease. Even in the absence of heart disease, acute and chronic hypoxia have been shown to promote sleep-related periodic breathing with... more
Background: Sleep disordered breathing is frequently observed in patients with cardiovascular disease. Even in the absence of heart disease, acute and chronic hypoxia have been shown to promote sleep-related periodic breathing with central apnea characterized by a repetitive reduction or lack of respiratory activity. Cyanotic congenital heart disease (CCHD) is associated with chronic hypoxia, regardless of whether an increase in pulmonary artery pressures coexists. Sleep aggravated hypoxia has been observed in many such patients, but it remains to be determined whether sleep disordered breathing is contributory. We, therefore, sought to assess sleep-related breathing pattern in patients with CCHD. Methods: Adults with CCHD, resting arterial oxygen saturation b 90%, and systemic ejection fraction N 40% were prospectively enrolled in a cross-sectional study. To assess sleep and respiratory indices, subjects underwent a standardized clinical appraisal that included arterial blood gas analysis and a comprehensive sleep study with an ambulatory device. An apnea–hypopnea index (AHI) ≥ 5/h was considered to indicate sleep apnea. Results: Ten adults with CCHD, aged 38 ± 11 years, completed the study. Seven patients had elevated pulmonary artery pressures, with a mean systolic pressure of 86.3 ± 18.1 mm Hg. All patients demonstrated normal sleep parameters. Oxygen saturation further declined in 5 patients during sleep. However, no associated alteration in respiratory parameters was observed and no significant arrhythmia. The mean AHI was 1.1 ± 1.0/h. No subject met the pre-defined criterion for sleep apnea. Conclusion: Although further oxygen desaturation may be observed during sleep in patients with CCHD, it occurs in the absence of sleep disordered breathing.
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Summary: To assess the topographical distribution of sleep spindles and K-complexes, four 15-minute samples of stage 2 sleep in a group of eight healthy young adults were analyzed. Results show that a majority of spindles generated are... more
Summary: To assess the topographical distribution of sleep spindles and K-complexes, four 15-minute samples of stage 2 sleep in a group of eight healthy young adults were analyzed. Results show that a majority of spindles generated are detected over central regions, and that K-complexes are markedly predominant over prefrontal and frontal regions. These findings are consistent with the single-spindle generator hypothesis and raise questions concerning the Rechtschaffen and Kales rules for scoring K-complexes. Key Words: Sleep ...
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Research Interests:
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Investigations into the role played by sleep in information processing have consistently shown that the retention of information is better when the memory storage is followed by a period of sleep than of waking. Less definitive evidence,... more
Investigations into the role played by sleep in information processing have consistently shown that the retention of information is better when the memory storage is followed by a period of sleep than of waking. Less definitive evidence, however, is available as to whether the better performance is mainly due to (a) reduction of interference during sleep, (b) slowing down of decay, or (c) consolidation processes at work during sleep. Important insights as to whether consolidation takes place during sleep have recently been provided by the thematic continuity of dreams elaborated in the same night and by the repeated incorporation of pre-sleep stimuli into dream contents. The analysis of such aspects of dreaming indicates that the items of information which are repeatedly accessed during sleep and elaborated for insertion into the ongoing dream experience are better retained at delayed recall. Finally, it is suggested that the use of the strategies applied in studying the information processing in normals may also be extended to sleep-disturbed individuals, in order to establish how memory functioning during sleep is influenced by sleep disturbances.
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The most recent consensus of the American Academy of Sleep Medicine is that parasomnias are “undesirable physical events or experiences that occur during entry into sleep, within sleep or during arousals from sleep”(1). Parasomnias are... more
The most recent consensus of the American Academy of Sleep Medicine is that parasomnias are “undesirable physical events or experiences that occur during entry into sleep, within sleep or during arousals from sleep”(1). Parasomnias are often considered to be normal sleep phenomena, especially in children, and do not in general have a serious impact on sleep quality or quantity. However, in some cases, injuries can result, psychological distress can ensue, and sleep disruption can seriously disturb the individual ...
To investigate differences in sleep spindle properties and scalp topography between patients with rapid eye movement sleep behaviour disorder (RBD) and healthy controls, whole-night polysomnograms of 35 patients diagnosed with RBD and 35... more
To investigate differences in sleep spindle properties and scalp topography between patients with rapid eye movement sleep behaviour disorder (RBD) and healthy controls, whole-night polysomnograms of 35 patients diagnosed with RBD and 35 healthy control subjects matched for age and sex were compared. Recordings included a 19-lead 10-20 electroencephalogram montage and standard electromyogram, electrooculogram, electrocardiogram and respiratory leads. Sleep spindles were automatically detected using a standard algorithm, and their characteristics (amplitude, duration, density, frequency and frequency slope) compared between groups. Topological analyses of group-discriminative features were conducted. Sleep spindles occurred at a significantly (e.g. t34 = -4.49; P = 0.00008 for C3) lower density (spindles∙min(-1) ) for RBD (mean ± SD: 1.61 ± 0.56 for C3) than for control (2.19 ± 0.61 for C3) participants. However, when distinguishing slow and fast spindles using thresholds individually adapted to the electroencephalogram spectrum of each participant, densities smaller (31-96%) for fast but larger (20-120%) for slow spindles were observed in RBD in all derivations. Maximal differences were in more posterior regions for slow spindles, but over the entire scalp for fast spindles. Results suggest that the density of sleep spindles is altered in patients with RBD and should therefore be investigated as a potential marker of future neurodegeneration in these patients.
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The final traumatic event recalled by Anna O. during her treatment with Josef Breuer was a terrifying hallucination she once had of a black snake attacking her ailing father. This event has been variously interpreted as indicating an... more
The final traumatic event recalled by Anna O. during her treatment with Josef Breuer was a terrifying hallucination she once had of a black snake attacking her ailing father. This event has been variously interpreted as indicating an underlying psychodynamic conflict, as a temporal lobe seizure, and as an hypnotic confabulation. We argue, however, that the hallucination--during which Anna O.'s arm was reportedly "asleep" due to nerve blockage--was probably a sleep paralysis nightmare. Sleep paralysis nightmares continue to be overlooked or misdiagnosed in clinical practice, and, in recent years, have been implicated in the controversy surrounding memories of trauma and sexual abuse.
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Abstract The goal of the present study was to quantify and localize brain electrical activity differences in REM sleep between right anatomical hemispherectomized patients and a matched control group. Z-statistic maps showed a significant... more
Abstract The goal of the present study was to quantify and localize brain electrical activity differences in REM sleep between right anatomical hemispherectomized patients and a matched control group. Z-statistic maps showed a significant increase in fast activities bands over the intact hemisphere
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ABSTRACT This communication investigates the impact on classifier evaluation of a high asymmetry between positive and negatives classes. It points out some necessary precautions when reporting classifier performances using... more
ABSTRACT This communication investigates the impact on classifier evaluation of a high asymmetry between positive and negatives classes. It points out some necessary precautions when reporting classifier performances using threshold-dependent statistics defined with the confusion matrix. It stresses that, in highly unbalanced datasets, reporting the positive predictive value (PPV) is more appropriate than reporting specificity. More elaborate variables such as F-measure and Matthews’ correlation coefficient may also provide a reliable portrait. It further concludes that, in many cases, only a small portion of the receiver operating characteristic (ROC) curve is actually useful, unless very low PPV are judged acceptable. Two remedies are proposed to complement the ROC curve: using a positive tradeoff curve (defined herein) or adding iso-PPV lines (i.e., lines of constant PPV) on the ROC graph. The observations reported in this study contribute to understanding of the impact of asymmetry on classifier performances. They also cast some doubt on the pertinence, when dealing with highly asymmetric problems, of using the area under the ROC curve for threshold-independent assessment of classifier performances.
ABSTRACT The domain of electroencephalography (EEG) has a long history of research and clinical applications. Its relative ease of deployment, low cost, and high availability have secured for this recording technique a place of choice in... more
ABSTRACT The domain of electroencephalography (EEG) has a long history of research and clinical applications. Its relative ease of deployment, low cost, and high availability have secured for this recording technique a place of choice in the neuroscience and neuromedecine armada. Given these qualities and its important user base, investigation of the central nervous system could largely benefit from the development of new analysis techniques for EEG recordings. This paper contributes to a better exploitation of EEG databases by proposing a new methodology to assess temporal displacements of transient activity of scalp action potential fields. This technique establishes relationships - through a cross-correlation analysis - between the time-frequency representations of different recording channels. An example application is given for the propagation of EEG sleep spindles but larger applicability to other transient waveforms recorded on dense arrays of sensors is also possible.
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As arousing as cyberspace may appear, many of its experiential qualities suggest that it is a dreamlike state. Very often cyberspace and dreaming both seem vividly real, even though this reality is only virtual. The existential similarity... more
As arousing as cyberspace may appear, many of its experiential qualities suggest that it is a dreamlike state. Very often cyberspace and dreaming both seem vividly real, even though this reality is only virtual. The existential similarity between cyberspace and dreaming realities is complex and largely unstudied, but its exploration could have profound implications for the future development of research in both domains. This paper investigates some qualities of virtual experience which characterize both cyberspace and dreaming, it proposes some concepts for understanding their similarity, and it discusses some of the potential implications a oneiric approach to virtual reality experience may have both for the development of cyberspace narratives and for our understanding of dream function.