Högskolan i Skövde

Posttraumatic symptoms, including nightmares, are more prevalent in World War II survivors than in the general population, but how war experiences have affected subsequent dream content in specific survivor populations remains less explored. In the present study, we used self -reports collected in 1973 from Polish Auschwitz survivors (N = 150; 45 women) to investigate the prevalence of posttraumatic symptoms, classified according to the DSM-5 diagnostic criteria for posttraumatic stress disorder (PTSD). Furthermore, we classified main themes, central emotions, and threatening events in the dreams (N = 632) of the survivors, comparing dreams recalled from before, during, and after the war. Of the respondents, 12.7% described experiencing all diagnostic criteria for PTSD. War-related themes were less common in dreams dreamt before than during the war but were most common after the war. Themes related to family and freedom were most likely to appear in dreams dreamt during than before or after the war. The most often occurring emotion was fear, and dreams from after the war were likely to contain more negative and less positive emotions than dreams dreamt during the war. The likelihoods of reporting threatening events and threats involving aggression were higher in dreams dreamt during than before the war and in dreams dreamt after than during the war. In conclusion, PTSD symptoms were common in Polish Auschwitz survivors 30 years after World War II, and the themes, emotions, and threatening events in their dreams seem to reflect lifelong posttraumatic dreaming. We interpret the results as lending support for the threat simulation theory of dreaming.

Episodic memories of emotionally salient and personally significant events are often incorporated into dreams, although rarely replayed identically to the original waking event except in replicative posttraumatic nightmares. We investigated, in five Swedish female 2004 Indian Ocean tsunami survivors, how episodic memories of the catastrophe were reflected in their dreams after trauma, both in retrospectively recalled nightmares and bad dreams, and in prospective dream diaries completed several months after the catastrophe. We also assessed whether the emotional and threatening dream content differed between the trauma and a matched control group. Based on the threat simulation theory, we predicted that the trauma group dreams would portray notable similarities with elements related to the original tsunami trauma, and that the trauma group would demonstrate a higher prevalence of negative emotional states, and a higher frequency of threatening dream events as well as more severe threats in their dreams. Only the first hypothesis was partially supported, with retrospective nightmares bearing higher similarity to the trauma experience than the prospective dream diary dreams. However, we observed no statistically significant differences in emotional or threatening dream content between the groups, suggesting that the trauma group participants were not suffering from significant posttraumatic dreaming at the time of systematic dream data collection. Yet, specific features of the trauma group dreams might be interpreted as remnants of episodic tsunami-related memories: Their dreams had a higher percentage of life-threatening events depicting realistic but improbable threats, and an analysis of water-related themes evidenced stressful themes related to waves.

In general, dreams are a novel but realistic simulation of waking social life, with a mixture of characters, motivations, scenarios, and positive and negative emotions. We propose that the sharing of dreams has an empathic effect on the dreamer and on significant others who hear and engage with the telling of the dream. Study 1 tests three correlations that are predicted by the theory of dream sharing and empathy: that trait empathy will be correlated with frequency of telling dreams to others, with frequency of listening to others’ dreams, and with trait attitude toward dreams (ATD) (for which higher scores indicate positive attitude). 160 participants completed online the Toronto Empathy Questionnaire and the Mannheim Dream Questionnaire. Pearson partial correlations were conducted, with age and sex partialled out. Trait empathy was found to be significantly associated with the frequency of listening to the dreams of others, frequency of telling one’s own dreams to others, and attitude toward dreams. Study 2 tests the effects of discussing dreams on state empathy, using an adapted version of the Shen (2010) state empathy scale, for 27 pairs of dream sharers and discussers. Dream discussion followed the stages of the Ullman (1996) dream appreciation technique. State empathy of the dream discusser toward the dream sharer was found to increase significantly as a result of the dream discussion, with a medium effect size, whereas the dream sharer had a small decrease in empathy toward the discusser. A proposed mechanism for these associations and effects is taken from the robust findings in the literature that engagement with literary fiction can induce empathy toward others. We suggest that the dream acts as a piece of fiction that can be explored by the dreamer together with other people, and can thus induce empathy about the life circumstances of the dreamer. We discuss the speculation that the story-like characteristics of adult human dreams may have been selected for in human evolution, including in sexual selection, as part of the selection for emotional intelligence, empathy, and social bonding.

This study replicated and extended a previous finding that the discussion of dreams increases the level of empathy toward the dreamer from those with whom the dream is discussed. The study addressed mediating variables for the empathy effect. Participants who already knew each other were recruited in dyads and were assigned dream-sharer and discusser roles. Each dyad used the Ullman dream appreciation technique to explore the relationship of the sharer’s dreams to recent experiences in the sharer’s life, with a maximum of 4 dream discussions per dyad (mean length of dreams = 140.15 words, mean discussion length = 23.72 min). The empathy of each member of a dyad toward the other was assessed using a 12-item state empathy questionnaire. A total of 44 participants (females = 26, males = 18, Mage = 26.70) provided empathy scores at baseline and after each dream discussion. For below median baseline empathy scorers, empathy of discussers toward their dream-sharer increased significantly as a result of the dream discussions, with medium effect size, η² = .39. Dream-sharers had a nonsignificant increase in empathy toward their discusser. Change in empathy was not linear across successive discussions, and was not related to length of dream reports, nor length of discussions. These findings of postsleep, social effects of dreaming, with possibly a group bonding function, go beyond theories of dreaming that have a within-sleep emotional or memory processing function for the individual. 

The snake detection hypothesis claims that predatory pressure from snakes has shaped the primate visual system, but we still know very little about how the brain processes evolutionarily important visual cues, and which factors are crucial for quick detection of snakes. We investigated how visual features modulate the electrophysiological markers of early attentional processes. In Experiment 1, we compared snake, rope, gun, and bird images to isolate the effects due to curvilinearity of the stimuli. The results showed that both snake and rope images elicited enhanced P1 and N1 event-related potential components as well as early posterior negativity (EPN). In Experiment 2, we studied whether nonthreatening curvilinear images (i.e., ropes) still elicit the enhanced electrophysiological responses when snake images are not presented as stimuli, and therefore the context does not provoke top-down attention to curvilinear shapes. Rope images still evoked an enhanced EPN, suggesting that curvilinear shapes are preferably captured by attentional processes. However, this effect was smaller than in Experiment 1, in which snake images were present. Thus, our results hint to the possibility that the perceptual context may interact with processing of shape information, drawing attention to curvilinear shapes when the presence of snakes is expectable. Furthermore, we observed that spatial frequency of the visual stimuli modulated especially the early electrophysiological responses, and decreased the differences between stimulus categories in EPN without completely eliminating them. The findings suggest that low-level and high-level mechanisms interact to give an attentional priority to potentially threatening stimuli.

Despite the complexity and methodological difficulties in defining the concept consciousness, it is a central concept in epileptology, and should thus be tractable for scientific analysis. In the present article, a two-dimensional model consisting of concepts related to the level and the contents of consciousness will be presented. This model has been found to be well suited for the description of seizure-induced alterations of consciousness, and is supported both by findings from neuroimaging and electrophysiological studies as well as from phenomenological studies. Further, we will review both traditional introspective methods as well as methods that have recently been developed or utilized in epilepsy research, summarize the main findings concerning first person experiences during epileptic seizures acquired with some of these methods, and discuss their strengths and weaknesses.

Epilepsy research suffers from a deficiency of systematic studies concerning the phenomenology of the contents of consciousness during seizures, partially because of the lack of suitable research methods. The Phenomenology of Consciousness Inventory (PCI), a standardized, valid, and reliable questionnaire, was used here to study which dimensions of the contents of consciousness are distorted during partial epileptic seizures compared with baseline. Further, the similarity of the altered pattern of subjective experiences across recurring seizures was also explored. Our results indicate that patients with epilepsy report alterations on most dimensions of the contents of consciousness in conjunction with seizures, but individual seizure experiences remain similar from one seizure to another. The PCI was found suitable for the assessment of subjective experiences during epileptic seizures and could be a valuable tool in providing new information about phenomenal consciousness in epilepsy in both the research and clinical settings.

A new content analysis method for systematically describing the phenomenology of subjective experiences in connection with partial epileptic seizures is described. Forty patients provided 262 descriptions of subjective experience relative to their partial epileptic seizures. The results revealed that subjective experiences during seizures consist mostly of sensory and bodily sensations, hallucinatory experiences, and thinking. The majority of subjective experiences during seizures are bizarre and distorted; nevertheless, the patients are able to engage in adequate behavior. To the best of our knowledge, this is the first study for which detailed subjective seizure descriptions were collected immediately after each seizure and the first study in which the content of verbal reports of subjective experiences during seizures, including both the ictal and postictal experiences, has been analyzed in detail.

Background: Surgery and diseases modify inflammatory responses and the immune system. Anesthetic agents also have effects on the human immune system but the responses they induce may be altered or masked by the surgical procedures or underlying illnesses. The aim of this study was to assess how single-drug dexmedetomidine and propofol anesthesia without any surgical intervention alter acute immunological biomarkers in healthy subjects. Methods: Thirty-five healthy, young male subjects were anesthetized using increasing concentrations of dexmedetomidine (n = 18) or propofol (n = 17) until loss of responsiveness (LOR) was detected. The treatment allocation was randomized. Multi-parametric immunoassays for the detection of 48 cytokines, chemokines and growth factors were used. Concentrations were determined at baseline and at the highest drug concentration for each subject. Results: The changes in the concentration of eotaxin (decrease after dexmedetomidine) and platelet-derived growth factor (PDGF, increase after propofol) were statistically significantly different between the groups. Significant changes were detected within both groups; the concentrations of monocyte chemotactic protein 1, chemokine ligand 27 and macrophage migration inhibitory factor were lower in both groups after the drug administration. Dexmedetomidine decreased the concentration of eotaxin, interleukin-18, interleukin-2Ra, stem cell factor, stem cell growth factor and vascular endothelial growth factor, and propofol decreased significantly the levels of hepatocyte growth factor, IFN-.-induced protein 10 and monokine induced by IFN-gamma, and increased the levels of interleukin-17, interleukin-5, interleukin-7 and PDGF. Conclusions: Dexmedetomidine seemed to have an immunosuppressive effect on the immune system whereas propofol seemed to induce mixed pro- and anti-inflammatory effects on the immune system. The choice of anesthetic agent could be relevant when treating patients with compromised immunological defense mechanisms. Trial registration: Before subject enrollment, the study was registered in the European Clinical Trials database (EudraCT number 2013-001496-21, The Neural Mechanisms of Anesthesia and Human Consciousness) and in ClinicalTrials.gov (Principal Investigator: Harry Scheinin, number NCT01889004, The Neural Mechanisms of Anesthesia and Human Consciousness, Part 2, on the 23rd of June 2013).

Background: Studying the effects of anaesthetic drugs on the processing of semantic stimuli could yield insights into how brain functions change in the transition from wakefulness to unresponsiveness. Here, we explored the N400 event-related potential during dexmedetomidine- and propofol-induced unresponsiveness. Methods: Forty-seven healthy subjects were randomised to receive either dexmedetomidine (n = 23) or propofol (n = 24) in this open-label parallel-group study. Loss of responsiveness was achieved by stepwise increments of pseudo-steady-state plasma concentrations, and presumed loss of consciousness was induced using 1.5 times the concentration required for loss of responsiveness. Pre-recorded spoken sentences ending either with an expected (congruous) or an unexpected (incongruous) word were presented during unresponsiveness. The resulting electroencephalogram data were analysed for the presence of the N400 component, and for the N400 effect defined as the difference between the N400 components elicited by congruous and incongruous stimuli, in the time window 300-600 ms post-stimulus. Recognition of the presented stimuli was tested after recovery of responsiveness. Results: The N400 effect was not observed during dexmedetomidine- or propofol-induced unresponsiveness. The N400 component, however, persisted during dexmedetomidine administration. The N400 component elicited by congruous stimuli during unresponsiveness in the dexmedetomidine group resembled the large component evoked by incongruous stimuli at the awake baseline. After recovery, no recognition of the stimuli heard during unresponsiveness occurred. Conclusions: Dexmedetomidine and propofol disrupt the discrimination of congruous and incongruous spoken sentences, and recognition memory at loss of responsiveness. However, the processing of words is partially preserved during dexmedetomidine-induced unresponsiveness.

There are several different approaches to analyze event-related potentials (ERPs) at single-subject level, and the aim of the current study is to provide information for choosing a method based on its ability to detect ERP effects and factors influencing the results. We used data from 79 healthy participants with EEG referenced to mastoid average and investigated the detection rate of auditory N400 effect in single-subject analysis using five methods: visual inspection of participant-wise averaged ERPs, analysis of variance (ANOVA) for amplitude averages in a time window, cluster-based non-parametric testing, a novel Bayesian approach and Studentized continuous wavelet transform (t-CWT). Visual inspection by three independent raters yielded N400 effect detection in 85% of the participants in at least one paradigm (active responding or passive listening), whereas ANOVA identified the effect in 68%, the cluster-method in 59%, the Bayesian method in 89%, and different versions of t-CWT in 22–59% of the participants. Thus, the Bayesian method was the most liberal and also showed the greatest concordance between the experimental paradigms (active/passive). ANOVA detected significant effect only in cases with converging evidence from other methods. The t-CWT and cluster-based method were the most conservative methods. As we show in the current study, different analysis methods provide results that do not completely overlap. The method of choice for determining the presence of an ERP component at single-subject level thus remains unresolved. Relying on a single statistical method may not be sufficient for drawing conclusions on single-subject ERPs. 

Background herent alpha electroencephalogram (EEG) rhythms in the frontal cortex have been correlated with the hypnotic effects of propofol and dexmedetomidine, but less is known about frontal connectivity as a state-specific correlate of unresponsiveness as compared with long-range connectivity. We aimed to distinguish dose- and state-dependent effects of dexmedetomidine and propofol on EEG connectivity. thods rty-seven healthy males received either dexmedetomidine (n=23) or propofol (n=24) as target-controlled infusion with stepwise increments until loss of responsiveness (LOR). We attempted to arouse participants during constant dosing (return of responsiveness [ROR]), and the target concentration was then increased 50% to achieve presumed loss of consciousness. We collected 64-channel EEG data and prefrontal–frontal and anterior–posterior functional connectivity in the alpha band (8–14 Hz) was measured using coherence and weighted phase lag index (wPLI). Directed connectivity was measured with directed phase lag index (dPLI). sults efrontal–frontal EEG-based connectivity discriminated the states at the different drug concentrations. At ROR, prefrontal–frontal connectivity reversed to the level observed before LOR, indicating that connectivity changes were related to unresponsiveness rather than drug concentration. Unresponsiveness was associated with emergence of frontal-to-prefrontal dominance (dPLI: –0.13 to –0.40) in contrast to baseline (dPLI: 0.01–0.02). Coherence, wPLI, and dPLI had similar capability to discriminate the states that differed in terms of responsiveness and drug concentration. In contrast, anterior–posterior connectivity in the alpha band did not differentiate LOR and ROR. nclusions cal prefrontal–frontal EEG-based connectivity reflects unresponsiveness induced by propofol or dexmedetomidine, suggesting its utility in monitoring the anaesthetised state with these agents. inical trial registration

Establishing the neural mechanisms responsible for the altered global states of consciousness during anesthesia and dissociating these from other drug-related effects remains a challenge in consciousness research. We investigated differences in brain activity between connectedness and disconnectedness by administering various anesthetics at concentrations designed to render 50% of the subjects unresponsive. One hundred and sixty healthy male subjects were randomized to receive either propofol (1.7 μg/ml; n = 40), dexmedetomidine (1.5 ng/ml; n = 40), sevoflurane (0.9% end-tidal; n = 40), S-ketamine (0.75 μg/ml; n = 20), or saline placebo (n = 20) for 60 min using target-controlled infusions or vaporizer with end-tidal monitoring. Disconnectedness was defined as unresponsiveness to verbal commands probed at 2.5-min intervals and unawareness of external events in a postanesthesia interview. High-resolution positron emission tomography (PET) was used to quantify regional cerebral metabolic rates of glucose (CMRglu) utilization. Contrasting scans where the subjects were classified as connected and responsive versus disconnected and unresponsive revealed that for all anesthetics, except S-ketamine, the level of thalamic activity differed between these states. A conjunction analysis across the propofol, dexmedetomidine and sevoflurane groups confirmed the thalamus as the primary structure where reduced metabolic activity was related to disconnectedness. Widespread cortical metabolic suppression was observed when these subjects, classified as either connected or disconnected, were compared with the placebo group, suggesting that these findings may represent necessary but alone insufficient mechanisms for the change in the state of consciousness.

IntroductionThe highly selective α₂-agonist dexmedetomidine has become a popular sedative for neurointensive care patients. However, earlier studies have raised concern that dexmedetomidine might reduce cerebral blood flow without a concomitant decrease in metabolism. Here, we compared the effects of dexmedetomidine on the regional cerebral metabolic rate of glucose (CMR_glu) with three commonly used anaesthetic drugs at equi-sedative doses.

MethodsOne hundred and sixty healthy male subjects were randomised to EC₅₀ for verbal command of dexmedetomidine (1.5 ng ml⁻¹; n=40), propofol (1.7 μg ml⁻¹; n=40), sevoflurane (0.9% end-tidal; n=40) or S-ketamine (0.75 μg ml⁻¹; n=20) or placebo (n=20). Anaesthetics were administered using target-controlled infusion or vapouriser with end-tidal monitoring. ¹⁸F-labelled fluorodeoxyglucose was administered 20 min after commencement of anaesthetic administration, and high-resolution positron emission tomography with arterial blood activity samples was used to quantify absolute CMR_glu for whole brain and 15 brain regions.

ResultsAt the time of [F¹⁸]fluorodeoxyglucose injection, 55% of dexmedetomidine, 45% of propofol, 85% of sevoflurane, 45% of S-ketamine, and 0% of placebo subjects were unresponsive. Whole brain CMR_glu was 63%, 71%, 71%, and 96% of placebo in the dexmedetomidine, propofol, sevoflurane, and S-ketamine groups, respectively (P<0.001 between the groups). The lowest CMR_glu was observed in nearly all brain regions with dexmedetomidine (P<0.05 compared with all other groups). With S-ketamine, CMR_gludid not differ from placebo.

ConclusionsAt equi-sedative doses in humans, potency in reducing CMR_glu was dexmedetomidine>propofol>ketamine=placebo. These findings alleviate concerns for dexmedetomidine-induced vasoconstriction and cerebral ischaemia.

Previous research indicates that the COVID-19 pandemic has affected dreaming negatively. We compared 1132 dreams collected with prospective two-week dream diary during the pandemic to 166 dreams collected before the pandemic. We hypothesized that the pandemic would increase the number of threatening events, threats related to diseases, and the severity of threats. We also hypothesized that dreams that include direct references to the pandemic will include more threatening events, more disease-related threats, and more severe threats. In contradiction with our hypotheses, results showed no differences between pandemic and pre-pandemic samples in the number of threats, threats related to diseases, or severe threats. However, dreams with direct references to the pandemic had more threats, disease-related threats, and severe threats. Our results thus do not suggest a significant overall increase in nightmarish or threatening dream content during the pandemic but show a more profound effect on a minority of dreams. 

Anesthetic-induced changes in the neural activity of the brain have been recently utilized as a research model to investigate the neural mechanisms of phenomenal consciousness. However, the anesthesiologic definition of consciousness as ‘‘responsiveness to the environment’’ seems to sidestep the possibility that an unresponsive individual may have subjective experiences. The aim of the present study was to analyze subjective reports in sessions where sedation and the loss of responsiveness were induced by dexmedetomidine, propofol, sevoflurane or xenon in a nonsurgical experimental setting. After regaining responsiveness, participants recalled subjective experiences in almost 60% of sessions. During dexmedetomidine sessions, subjective experiences were associated with shallower ‘‘depth of sedation’’ as measured by an electroencephalography-derived anesthesia depth monitor. Results confirm that subjective experiences may occur during clinically defined unresponsiveness, and that studies aiming to investigate phenomenal consciousness under sedative and anesthetic effects should control the subjective state of unresponsive participants with post-recovery interviews.

A new experimental paradigm called "Early-Night Serial Awakenings" (ENSA) was explored to find out its strengths and weaknesses for psychophysiological studies of NREM sleep dreaming. Five participants spent 20 experimental nights in the sleep laboratory, and were serially awakened with approximately 24-minute intervals during Stages 2 and 3 of NREM sleep. As a total, 164 awakenings were conducted during the sessions that lasted on average 193 min. Altogether, 30% of NREM sleep awakenings led to dream reports, 39% to reports of white dreaming, and 31% to reports of dreamless sleep. Results also show that sleep EEG spectral power, dream recall frequency as well as dream complexity remained stable throughout the serial awakening sessions. We conclude that, as ENSA dreams appeared to be static and very limited in content, the paradigm we identified could be used in future studies to reveal the psychophysiological mechanisms of relatively simple forms of early-night NREM sleep dreaming. (c) 2009 Elsevier B.V. All rights reserved.

Dream diaries and reports of daytime waking thought were collected from five schizophrenia patients and matched controls. It was more difficult for blind judges to differentiate the patients' than the controls' dream reports from reports of waking thought, and patients reported shorter but more bizarre dreams than did the controls.

Recently, cortical correlates of specific dream contents have been reported, such as the activation of the sensorimotor cortex during dreamed hand clenching. Yet, despite a close resemblance of such activation patterns to those seen during the corresponding wakeful behaviour, the causal mechanisms underlying specific dream contents remain largely elusive. Here, we aimed to investigate the causal role of the sensorimotor cortex in generating movement and bodily sensations during REM sleep dreaming. Following bihemispheric transcranial direct current stimulation (tDCS) or sham stimulation, guided by functional mapping of the primary motor cortex, naive participants were awakened from REM sleep and responded to a questionnaire on bodily sensations in dreams. Electromyographic (EMG) and electroencephalographic (EEG) recordings were used to quantify physiological changes during the preceding REM period. We found that tDCS, compared to sham stimulation, significantly decreased reports of dream movement, especially of repetitive actions. Other types of bodily experiences, such as tactile or vestibular sensations, were not affected by tDCS, confirming the specificity of stimulation effects to movement sensations. In addition, tDCS reduced EEG interhemispheric coherence in parietal areas and affected the phasic EMG correlation between both arms. These findings show that a complex temporal reorganization of the motor network co-occurred with the reduction of dream movement, revealing a link between central and peripheral motor processes and movement sensations of the dream self. tDCS over the sensorimotor cortex interferes with dream movement during REM sleep, which is consistent with a causal contribution to dream experience and has broader implications for understanding the neural basis of self-experience in dreams. © 2020, The Author(s).

BACKGROUND: Pharmacometabolomics uses large-scale data capturing methods to uncover drug-induced shifts in the metabolic profile. The specific effects of anaesthetics on the human metabolome are largely unknown.

OBJECTIVE: We aimed to discover whether exposure to routinely used anaesthetics have an acute effect on the human metabolic profile.

DESIGN: Randomised, open-label, controlled, parallel group, phase IV clinical drug trial.

SETTING: The study was conducted at Turku PET Centre, University of Turku, Finland, 2016 to 2017.

PARTICIPANTS: One hundred and sixty healthy male volunteers were recruited. The metabolomic data of 159 were evaluable.

INTERVENTIONS: Volunteers were randomised to receive a 1-h exposure to equipotent doses (EC50 for verbal command) of dexmedetomidine (1.5 ng ml-1; n = 40), propofol (1.7 μg ml-1; n = 40), sevoflurane (0.9% end-tidal; n = 39), S-ketamine (0.75 μg ml-1; n = 20) or placebo (n = 20).

MAIN OUTCOME MEASURES: Metabolite subgroups of apolipoproteins and lipoproteins, cholesterol, glycerides and phospholipids, fatty acids, glycolysis, amino acids, ketone bodies, creatinine and albumin and the inflammatory marker GlycA, were analysed with nuclear magnetic resonance spectroscopy from arterial blood samples collected at baseline, after anaesthetic administration and 70 min postanaesthesia.

RESULTS: All metabolite subgroups were affected. Statistically significant changes vs. placebo were observed in 11.0, 41.3, 0.65 and 3.9% of the 155 analytes in the dexmedetomidine, propofol, sevoflurane and S-ketamine groups, respectively. Dexmedetomidine increased glucose, decreased ketone bodies and affected lipoproteins and apolipoproteins. Propofol altered lipoproteins, fatty acids, glycerides and phospholipids and slightly increased inflammatory marker glycoprotein acetylation. Sevoflurane was relatively inert. S-ketamine increased glucose and lactate, whereas branched chain amino acids and tyrosine decreased.

CONCLUSION: A 1-h exposure to moderate doses of routinely used anaesthetics led to significant and characteristic alterations in the metabolic profile. Dexmedetomidine-induced alterations mirror α2-adrenoceptor agonism. Propofol emulsion altered the lipid profile. The inertness of sevoflurane might prove useful in vulnerable patients. S-ketamine induced amino acid alterations might be linked to its suggested antidepressive properties.

TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02624401. URL: https://clinicaltrials.gov/ct2/show/NCT02624401.

Background

This exploratory study aimed to investigate whether dexmedetomidine, propofol, sevoflurane, and S-ketamine affect oxylipins and bile acids, which are functionally diverse molecules with possible connections to cellular bioenergetics, immune modulation, and organ protection.

Methods

In this randomised, open-label, controlled, parallel group, Phase IV clinical drug trial, healthy male subjects (n=160) received equipotent doses (EC50 for verbal command) of dexmedetomidine (1.5 ng ml−1; n=40), propofol (1.7 μg ml−1; n=40), sevoflurane (0.9% end-tidal; n=40), S-ketamine (0.75 μg ml−1; n=20), or placebo (n=20). Blood samples for tandem mass spectrometry were obtained at baseline, after study drug administration at 60 and 130 min from baseline; 40 metabolites were analysed.

Results

Statistically significant changes vs placebo were observed in 62.5%, 12.5%, 5.0%, and 2.5% of analytes in dexmedetomidine, propofol, sevoflurane, and S-ketamine groups, respectively. Data are presented as standard deviation score, 95% confidence interval, and P-value. Dexmedetomidine induced wide-ranging decreases in oxylipins and bile acids. Amongst others, 9,10-dihydroxyoctadecenoic acid (DiHOME) –1.19 (–1.6; –0.78), P<0.001 and 12,13-DiHOME –1.22 (–1.66; –0.77), P<0.001 were affected. Propofol elevated 9,10-DiHOME 2.29 (1.62; 2.96), P<0.001 and 12,13-DiHOME 2.13 (1.42; 2.84), P<0.001. Analytes were mostly unaffected by S-ketamine. Sevoflurane decreased tauroursodeoxycholic acid (TUDCA) –2.7 (–3.84; –1.55), P=0.015.

Conclusions

Dexmedetomidine-induced oxylipin alterations may be connected to pathways associated with organ protection. In contrast to dexmedetomidine, propofol emulsion elevated DiHOMEs, oxylipins associated with acute respiratory distress syndrome, and mitochondrial dysfunction in high concentrations. Further research is needed to establish the behaviour of DIHOMEs during prolonged propofol/dexmedetomidine infusions and to verify the sevoflurane-induced reduction in TUDCA, a suggested neuroprotective agent.

Clinical trial registration

NCT02624401.

Nightmares are vivid, extended, and emotionally negative or negative dreams that awaken the dreamer. While sporadic nightmares and bad dreams are common and generally harmless, frequent nightmares often reflect underlying pathologies of emotional regulation. Indeed, insomnia, depression, anxiety, or alcohol use have been associated with nightmares in epidemiological and clinical studies. However, the connection between nightmares and their comorbidities are poorly understood. Our goal was to examine the genetic risk factors for nightmares and estimate correlation or causality between nightmares and comorbidities. We performed a genome-wide association study (GWAS) in 45,255 individuals using a questionnaire-based assessment on the frequency of nightmares during the past month and genome-wide genotyping data. While the GWAS did not reveal individual risk variants, heritability was estimated at 5%. In addition, the genetic correlation analysis showed a robust correlation (rg > 0.4) of nightmares with anxiety (rg = 0.671, p = 7.507e−06), depressive (rg = 0.562, p = 1.282e−07) and posttraumatic stress disorders (rg = 0.4083, p = 0.0152), and personality trait neuroticism (rg = 0.667, p = 4.516e−07). Furthermore, Mendelian randomization suggested causality from insomnia to nightmares (beta = 0.027, p = 0.0002). Our findings suggest that nightmares share genetic background with psychiatric traits and that insomnia may increase an individual’s liability to experience frequent nightmares. Given the significant correlations with psychiatric and psychological traits, it is essential to grow awareness of how nightmares affect health and disease and systematically collect information about nightmares, especially from clinical samples and larger cohorts. 

Background: Experiences during anaesthetic-induced unresponsiveness have previously been investigated by interviews after recovery. To explore whether experiences occur during drug administration, we interviewed participants during target-controlled infusion (TCI) of dexmedetomidine or propofol and after recovery. Methods: Healthy participants received dexmedetomidine (n = 23) or propofol (n = 24) in stepwise increments until loss of responsiveness (LOR1). During TCI we attempted to arouse them for interview (return of responsiveness, ROR1). After the interview, if unresponsiveness ensued with the same dose (LOR2), the procedure was repeated (ROR2). Finally, the concentration was increased 1.5-fold to achieve presumable loss of consciousness (LOC), infusion terminated, and the participants interviewed upon recovery (ROR3). An emotional sound stimulus was presented during LORs and LOC, and memory for stimuli was assessed with recognition task after recovery. Interview transcripts were content analysed. Results: Of participants receiving dexmedetomidine, 18/23 were arousable from LOR1 and LOR2. Of participants receiving propofol, 10/24 were arousable from LOR1 and two of four were arousable from LOR2. Of 93 interviews performed, 84% included experiences from periods of unresponsiveness (dexmedetomidine 90%, propofol 74%). Internally generated experiences (dreaming) were present in 86% of reports from unresponsive periods, while externally generated experiences (awareness) were rare and linked to brief arousals. No within drug differences in the prevalence or content of experiences during infusion vs after recovery were observed, but participants receiving dexmedetomidine reported dreaming and awareness more often. Participants receiving dexmedetomidine recognised the emotional sounds better than participants receiving propofol (42% vs 15%), but none reported references to sounds spontaneously. Conclusion: Anaesthetic-induced unresponsiveness does not induce unconsciousness or necessarily even disconnectedness.

To understand how anesthetics with different molecular mechanisms affect consciousness, we explored subjective experiences recalled after responsive and unresponsive sedation induced with equisedative doses of dexmedetomidine, propofol, sevoflurane, and S-ketamine in healthy male participants (N = 140). The anesthetics were administered in experimental setting using target-controlled infusion or vapouriser for one hour. Interviews conducted after anesthetic administration revealed that 46.9% (n = 46) of arousable participants (n = 98) reported experiences, most frequently dreaming or memory incorporation of the setting. Participants receiving dexmedetomidine reported experiences most often while S-ketamine induced the most multimodal experiences. Responsiveness at the end of anesthetic administration did not affect the prevalence or content of reported experiences. These results demonstrate that subjective experiences during responsive and unresponsive sedation are common and anesthetic agents with different molecular mechanisms of action may have different effects on the prevalence and complexity of the experiences, albeit in the present sample the differences between drugs were minute. 

Based on biological realism, that is, the philosophical assumption that con-sciousness is a real natural biological phenomenon in the brain, we argue that dreaming is a pure form of phenomenality, and suggest that the dreaming brain could be used as a model system for consciousness. The dreaming brain offers the most challenging model system that represents all the theoretically and philosophically interesting features of consciousness. Although difficult to study experimentally, the dreaming brain is the model system that fully preserves all the essential features of consciousness, and cannot be ignored by any theory that aims to explain consciousness.

Malcolm-Smith, Solms, Turnbull and Treduoux (Malcolm-Smith, S., Solms, M., Turnbull, O., & Tredoux, C. (2008). Threat in dreams; An adaptiation? Consciousness and Cognition, 17, 1281-1291.) have made an attempt to test the Threat-Simulation Theory (TST), a theory offering an evolutionary psychological explanation for the function of dreaming (Revonsuo, A. (2000a). The reinterpretation of dreams: An evolutionary hypothesis of the function of dreaming. Behavioural and Brain Sciences, 23(6), 877-901). Malcolm-Smith et al. argue that empirical evidence from their own study as well as from some other studies in the literature does not support the main predictions of the TST: that threatening events are frequent and overrepresented in dreams, that exposure to real threats activates the threat-simulation system, and that dream threats contain realistic rehearsals of threat avoidance responses. Other studies, including or own, have come up with results and conclusions that are in conflict with those of Malcolm-Smith et al. In this commentary, we provide an analysis of the sources of these disagreements, and their implications to the TST. Much of the disagreement seems to stem from differing interpretations of the theory and, consequently, of differing methods to test it.

Objectives: The objective of this study was to investigate how blood pressure, sleep architecture, sleep-disordered breathing, body habitus, and levels of serum follicle-stimulating hormone are associated with symptoms of insomnia and sleep quality during menopausal transition.

Methods: 64 healthy premenopausal women (aged 45–47 years) were recruited to the study. Data were collected at baseline and at 10-year follow-up during sleep laboratory and laboratory visits. A sleep questionnaire was used to evaluate sleep quality and insomnia symptoms. Data were analysed using multiple linear and logistic regression with a backward method.

Results: During the menopausal transition, a change in insomnia symptoms was associated with a change in morning systolic blood pressure (β = 0.114 (CI95% 0.023–0.205), p = 0.016). At follow-up, at the age of 56, a higher percentage of REM sleep was associated with a lower odds of restless sleep (OR = 0.842 (95 % CI 0.742–0.954), p = 0.007), while both higher systolic and diastolic evening blood pressure was associated with an increased odds of morning tiredness. OR = 1.047 (95 % CI 1.003–1.092), p = 0.034 and OR = 1.126 (95 % CI 1.018–1.245), p = 0.007, respectively.

Conclusions: In healthy midlife women, a change blood pressure is related to the development of insomnia symptoms during menopausal transition. In postmenopausal women, a high evening blood pressure may be associated with morning tiredness and a reduced amount of REM sleep may be perceived as restless sleep. 

Sleep problems, especially nightmares and insomnia, often accompany depression. This study investigated how nightmares, symptoms of insomnia, chronotype and sleep duration associate with seasonal affective disorder, a special form of depression. Additionally, it was noted how latitude, a proxy for photoperiod, and characteristics of the place of residence affect the prevalence of seasonal affective disorder and sleep problems. To study these questions, data from FINRISK 2012 study were used. FINRISK 2012 consists of a random population sample of Finnish adults aged 25–74 years (n = 4905) collected during winter from Finnish urban and rural areas spanning the latitudes of 60°N to 66°N. The Seasonal Pattern Assessment Questionnaire was used to assess symptoms of seasonal affective disorder. Participants with symptoms of seasonal affective disorder had significantly increased odds of experiencing frequent nightmares and symptoms of insomnia, and they were more often evening chronotypes. Associations between latitude, population size and urbanicity with seasonal affective disorder symptoms and sleep disturbances were generally not significant, although participants living in areas bordering urban centres had less sleep problems than participants from other regions. These data show that the prevalence of seasonal affective disorder was not affected by latitude. 

Study Objectives: To investigate the prevalence of nightmares among the Finnish general adult population during 1972-2007 and the association between nightmare prevalence and symptoms of insomnia, depression, and anxiety in World War II veterans. Design: Eight independent cross-sectional population surveys of the National FINRISK Study conducted in Finland in 1972, 1977, 1982, 1987, 1992, 1997, 2002, and 2007. Setting: Epidemiologic. Participants: A total of 69,813 people (33,811 men and 36,002 women) age 25-74 years. Interventions: N/A. Measurements and Results: The investigation of nightmare prevalence and insomnia, depression, and anxiety symptoms was based on questionnaires completed by the participants. Among the whole sample, 3.5% of the men and 4.8% of the women reported frequent nightmares (P < 0.0001 for sex difference), but the prevalence was affected by the age of participants and the year of the survey. Nightmare prevalence increased with age, particularly among the men. The number of people reporting occasional nightmares increased roughly by 20% for both sexes from 1972 to 2007 (P < 0.0001). Participants with war experiences reported more frequent nightmares and symptoms of insomnia, depression, and anxiety than participants without such experiences (P < 0.0001). Conclusions: Prevalence of nightmares was affected by the sex and age of the participants, and occasional nightmares have become more common in Finland. Exposure to war elevates nightmare prevalence as well as insomnia, depression, and anxiety symptoms even decades after the war; large numbers of war veterans can affect nightmare prevalence on population level.

STUDY OBJECTIVES: To identify risk factors for experiencing nightmares among the Finnish general adult population. The study aimed to both test whether previously reported correlates of frequent nightmares could be reproduced in a large population sample and to explore previously unreported associations.

DESIGN: Two independent cross-sectional population surveys of the National FINRISK Study.

SETTING: Age- and sex-stratified random samples of the Finnish population in 2007 and 2012.

PARTICIPANTS: A total of 13,922 participants (6,515 men and 7,407 women) aged 25-74 y.

INTERVENTIONS: N/A.

MEASUREMENTS AND RESULTS: Nightmare frequency as well as several items related to socioeconomic status, sleep, mental well-being, life satisfaction, alcohol use, medication, and physical well-being were recorded with a questionnaire. In multinomial logistic regression analysis, a depression-related negative attitude toward the self (odds ratio [OR] 1.32 per 1-point increase), insomnia (OR 6.90), and exhaustion and fatigue (OR 6.86) were the strongest risk factors for experiencing frequent nightmares (P < 0.001 for all). Sex, age, a self-reported impaired ability to work, low life satisfaction, the use of antidepressants or hypnotics, and frequent heavy use of alcohol were also strongly associated with frequent nightmares (P < 0.001 for all).

CONCLUSIONS: Symptoms of depression and insomnia were the strongest predictors of frequent nightmares in this dataset. Additionally, a wide variety of factors related to psychological and physical well-being were associated with nightmare frequency with modest effect sizes. Hence, nightmare frequency appears to have a strong connection with sleep and mood problems, but is also associated with a variety of measures of psychological and physical well-being.

Nightmares are intensive dreams with negative emotional tone. Frequent nightmares can pose a serious clinical problem and in 2001, Tanskanen et al. found that nightmares increase the risk of suicide. However, the dataset used by these authors included war veterans in whom nightmare frequency -and possibly also suicide risk -is elevated. Therefore, re-examination of the association between nightmares and suicide in these data is warranted. We investigated the relationship between nightmares and suicide both in the general population and war veterans in Finnish National FINRISK Study from the years 1972 to 2012, a dataset overlapping with the one used in the study by Tanskanen et al. Our data comprise 71,068 participants of whom 3139 are war veterans. Participants were followed from their survey participation until the end of 2014 or death. Suicides (N = 398) were identified from the National Causes of Death Register. Frequent nightmares increase the risk of suicide: The result of Tanskanen et al. holds even when war experiences are controlled for. Actually nightmares are not significantly associated with suicides among war veterans. These results support the role of nightmares as an independent risk factor for suicide instead of just being proxy for history of traumatic experiences.

BACKGROUND

Differentiating drug-related changes and state-related changes on the electroencephalogram during anesthetic-induced unconsciousness has remained a challenge. To distinguish these, we designed a rigorous experimental protocol with two drugs known to have distinct molecular mechanisms of action. We hypothesized that drug- and state-related changes can be separated.

METHODS: 

Forty-seven healthy participants were randomized to receive dexmedetomidine (n = 23) or propofol (n = 24) as target-controlled infusions until loss of responsiveness. Then, an attempt was made to arouse the participant to regain responsiveness while keeping the drug infusion constant. Finally, the concentration was increased 1.5-fold to achieve presumable loss of consciousness. We conducted statistical comparisons between the drugs and different states of consciousness for spectral bandwidths, and observed how drug-induced electroencephalogram patterns reversed upon awakening. Cross-frequency coupling was also analyzed between slow-wave phase and alpha power.

RESULTS: 

Eighteen (78%) and 10 (42%) subjects were arousable during the constant drug infusion in the dexmedetomidine and propofol groups, respectively (P = 0.011 between the drugs). Corresponding with deepening anesthetic level, slow-wave power increased, and a state-dependent alpha anteriorization was detected with both drugs, especially with propofol. Negative phase-amplitude coupling before and during loss of responsiveness frontally and positive coupling during the highest drug concentration posteriorly were observed in the propofol but not in the dexmedetomidine group.

CONCLUSIONS: 

Electroencephalogram effects of dexmedetomidine and propofol are strongly drug- and state-dependent. Changes in slow-wave and alpha activity seemed to best detect different states of consciousness.

What happens in the brain when conscious awareness of the surrounding world fades? We manipulated consciousness in two experiments in a group of healthy males and measured brain activity with positron emission tomography. Measurements were made during wakefulness, escalating and constant levels of two anesthetic agents (Experiment 1, n=39) and during sleep-deprived wakefulness and Non-Rapid Eye Movement sleep (Experiment 2, n=37). In Experiment 1, the subjects were randomized to receive either propofol or dexmedetomidine until unresponsiveness. In both experiments, forced awakenings were applied to achieve rapid recovery from an unresponsive to a responsive state, followed by immediate and detailed interviews of subjective experiences during the preceding unresponsive condition. Unresponsiveness rarely denoted unconsciousness, as the majority of the subjects had internally generated experiences. Unresponsive anesthetic states and verified sleep stages, where a subsequent report of mental content included no signs of awareness of the surrounding world, indicated a disconnected state. Functional brain imaging comparing responsive and connected vs. unresponsive and disconnected states of consciousness during constant anesthetic exposure revealed that activity of the thalamus, cingulate cortices and angular gyri are fundamental for human consciousness. These brain structures were affected independent from the pharmacologic agent, drug concentration and direction of change in the state of consciousness. Analogous findings were obtained when consciousness was regulated by physiological sleep. State-specific findings were distinct and separable from the overall effects of the interventions, which included widespread depression of brain activity across cortical areas. These findings identify a central core brain network critical for human consciousness. SIGNIFICANCE STATEMENT Trying to understand the biological basis of human consciousness is currently one of the greatest challenges of neuroscience. While the loss and return of consciousness regulated by anesthetic drugs and physiological sleep are employed as model systems in experimental studies on consciousness, previous research results have been confounded by drug effects, by confusing behavioral "unresponsiveness" and internally generated consciousness, and by comparing brain activity levels across states that differ in several other respects than only consciousness. Here, we present carefully designed studies that overcome many previous confounders and for the first time reveal the neural mechanisms underlying human consciousness and its disconnection from behavioral responsiveness, both during anesthesia and during normal sleep, and in the same study subjects.

STUDY OBJECTIVES: The diagnosis of a nightmare disorder is based on clinically significant distress caused by the nightmares, eg, sleep or mood disturbances during the day. The question what factors might be associated with nightmare distress in addition to nightmares frequency is not well studied.

METHODS: Overall, 1,474 persons (893 women, 581 men) completed an online survey. Nightmare distress was measured with the Nightmare Distress Questionnaire.

RESULTS: The findings indicated that nightmare distress, measured by the Nightmare Distress Questionnaire, correlated with a variety of factors in addition to nightmare frequency: neuroticism, female sex, low education, extraversion, low agreeableness, and sensation seeking. Moreover, the percentage of replicative trauma-related nightmares was also associated with higher nightmare distress.

CONCLUSIONS: A large variety of factors are associated with nightmare distress, a finding that is of clinical importance. The construct harm avoidance, however, was not helpful in explaining interindividual differences in nightmare distress. Furthermore, the relationship between nightmare distress and other factors, eg, education or agreeableness, is not yet understood.

Dreams are experiences that occur during sleep, while we are disconnected from the environment. Thanks to recent progress in neuroimaging techniques, it is now becoming possible to relate dream features to specific patterns of brain activity. Some conditions occurring in patients with neurological disorders, such as lucid dreams and parasomnias, not only have diagnostic value, but also offer a window into the dream process. They show that dreaming is reflected in physiological signals, behaviours, and brain activity patterns, and that the body can enact dream content. Yet, the dream body can also be distinct from the real body; in their dreams, patients with congenital paraplegia can walk, those with sleep apnoea rarely suffocate, and phantom limb pain can disappear. These conditions provide valuable models for future studies investigating the mechanisms that underlie oneiric experiences. 

This study demonstrates that different methods for measuring emotional experiences in dreams — self-ratings of dreams using emotion rating scales versus external ratings in the form of content analysis of narrative dream reports — can lead to strikingly different results and contradicting conclusions about the emotional content of home dreams. During 3 consecutive weeks, every morning upon awakening, 44 participants (16 men, 28 women, average age 26.9± 5.1 years) reported their dreams and rated their emotional experiences in those dreams using the modified Differential Emotions Scale. Two external judges rated emotional experiences inthe same 552 (M = 12.55 ± 5.72) home dream reports using the same scale. Comparison of the 2 methods showed that with self-ratings dreams were rated as more emotional and more positive than with external ratings. Moreover, whereas with self-ratings the majority of dreams was rated as positively valenced, with external ratings the majority of dream reports was rated as negatively valenced. Although self- and external ratings converge, at least partially, in the measurement of negative emotional experiences, they diverge greatly in the measurement of positive emotional experiences. On one hand, this discrepancy may result from different biases inherent in the 2 measurement methods highlighting the need to develop better methods for measuring emotional experiences. On the other hand, self- and external ratings may capture different phenomena and should thus be considered complementary and used concurrently. Nevertheless, results suggest that negative emotional experiences can be measured in a more valid and reliable manner than positive emotional experiences.

Affective experiences are central not only to our waking life but also to rapid eye movement(REM) sleep dreams. Despite our increasing understanding of the neural correlates of dreaming, we know little about the neural correlates of dream affect. Frontal alpha asymmetry (FAA) is considered a marker of affective states and traits as well as affect regulation in the waking state. Here, we explored whether FAA during REM sleep and during evening resting wakefulness is related to affective experiences in REM sleep dreams. EEG recordings were obtained from 17humanparticipants (7men)whospent 2 nights in the sleep laboratory. Participants were awakened 5minafter the onset of everyREMstage after which they provided a dream report and rated their dream affect. Two-minute preawakening EEG segments were analyzed. Additionally, 8 min of evening presleep and morning postsleep EEG were recorded during resting wakefulness. Mean spectral power in the alpha band (8 –13 Hz and correspondingFAAwere calculated over the frontal (F4-F3) sites. Results showed that FAA during REM sleep, and during evening resting wakefulness, predicted ratings of dream anger. This suggests that individuals with greater alpha power in the right frontal hemisphere may be less able to regulate (i.e., inhibit) strong affective states, such as anger, in dreams. Additionally, FAA was positively correlated across wakefulness and REM sleep. Together, these findings imply that FAA may serve as a neural correlate of affect regulation not only in the waking but also in the dreaming state.

The aim of this study was to compare the emotional content of dream reports collected at home upon morning awakenings with those collectedin the laboratory upon early and late rapid eye movement (REM) sleep awakenings. Eighteen adults (11 women, seven men; mean age = 25.89 ± 4.85) wrote down their home dreams every morning immediately upon awakening during a 7-day period. Participants also spent two non-consecutive nights in the sleep laboratory where they were awoken 5 min into each continuous REM sleep stage, upon which they gave a verbal dream report. The content of a total of 151 home and 120 laboratory dream reports was analysed by two blind judges using the modified Differential Emotions Scale. It was found that: (1) home dream reports were more emotional than laboratory early REM dream reports, but not more emotional than laboratory late REM dream reports; (2) home dream reports contained a higher density of emotions than laboratory (early or late REM) dream reports; and (3) home dream reports were more negative than laboratory dream reports, but differences between home and early REM reports were larger than those between home and late REM reports. The results suggest that differences between home and laboratory dream reports in overall emotionality may be due to the time of night effect. Whether differences in the density of emotions and negative emotionality are due to sleep environment or due to different reporting procedures and time spent in a sleep stage, respectively, remains to be determined in future studies.

Emotions are central in dreams, specifically in rapid eye movement sleep dreams. Despite a wealth of research on the emotional content of dreams, there is little consensus about the overall emotionality and predominant valence of dreams or about the prevailing specific emotions in dreams. Previous contradictory findings are arguably due to unresolved methodological issues. However, studies that have directly investigated these methodological issues are scarce. In this presentation three studies that investigated the effect of study methodology on the frequency, valence and phenomenological content of dream emotions are discussed. The studies demonstrate that the use of different methods for rating dream emotions (participants who experience the dream vs external judges who analysed the respective dream report) and for collecting dream reports (home vs laboratory setting) leads to very different results and conclusions about the emotional content of dreams. As such, these studies highlight the importance of carefully considering study methodology when conducting and interpreting dream (emotional) content studies.

Despite a surge of studies on the effects of COVID-19 on our well-being, we know little about how the pandemic is reflected in people's spontaneous thoughts and experiences, such as mind-wandering (or daydreaming) during wakefulness and dreaming during sleep. We investigated whether and how COVID-19-related general concern, anxiety, and daily worry are associated with the daily fluctuation of the affective quality of mind-wandering and dreaming, and to what extent these associations can be explained by poor sleep quality. We used ecological momentary assessment by asking participants to rate the affect they experienced during mind-wandering and dreaming in daily logs over a 2-week period. Our preregistered analyses based on 1,755 dream logs from 172 individuals and 1,496 mind-wandering logs from 152 individuals showed that, on days when people reported higher levels of negative affect and lower levels of positive affect during mind-wandering, they experienced more worry. Only daily sleep quality was associated with affect experienced during dreaming at the within-person level: on nights with poorer sleep quality people reported experiencing more negative and less positive affect in dreams and were more likely to experience nightmares. However, at the between-person level, individuals who experienced more daily COVID-19 worry during the study period also reported experiencing more negative affect during mind-wandering and during dreaming. As such, the continuity between daily and nightly experiences seems to rely more on stable trait-like individual differences in affective processing. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Affective experiences occur across the wake-sleep cycle—from active wakefulness to resting wakefulness (i.e., mind-wandering) to sleep (i.e., dreaming). Yet, we know little about the dynamics of affect across these states. We compared the affective ratings of waking, mind-wandering, and dream episodes. Results showed that mind-wandering was more positively valenced than dreaming, and that both mind-wandering and dreaming were more negatively valenced than active wakefulness. We also compared participants’ self-ratings of affect with external ratings of affect (i.e., analysis of affect in verbal reports). With self-ratings all episodes were predominated by positive affect. However, the affective valence of reports changed from positively valenced waking reports to affectively balanced mind-wandering reports to negatively valenced dream reports. These findings show that (1) the positivity bias characteristic to waking experiences decreases across the wake-sleep continuum, and (2) conclusions regarding affective experiences depend on whether self-ratings or verbal reports describing these experiences are analysed.

We investigated whether inconsistencies in previous studies regarding emotional experiencesin dreams derive from whether dream emotions are self-rated or externally evaluated.Seventeen subjects were monitored with polysomnography in the sleep laboratoryand awakened from every rapid eye movement (REM) sleep stage 5 min after the onsetof the stage. Upon awakening, participants gave an oral dream report and rated their dreamemotions using the modified Differential Emotions Scale, whereas external judges rated theparticipants’ emotions expressed in the dream reports, using the same scale. The twoapproaches produced diverging results. Self-ratings, as compared to external ratings,resulted in greater estimates of (a) emotional dreams; (b) positively valenced dreams;(c) positive and negative emotions per dream; and (d) various discrete emotions representedin dreams. The results suggest that this is mostly due to the underrepresentationof positive emotions in dream reports. Possible reasons for this discrepancy are discussed.

Based on the Social Simulation Theory of dreaming (SST), we studied the effects of voluntary social seclusion on dream content and sleep structure. Specifically, we studied the Compensation Hypothesis, which predicts social dream contents to increase during social seclusion, the Sociality Bias – a ratio between dream and wake interactions – and the Strengthening Hypothesis, which predicts an increase in familiar dream characters during seclusion. Additionally, we assessed changes in the proportion of REM sleep. Sleep data and dream reports from 18 participants were collected preceding (n = 94), during (n = 90) and after (n = 119) a seclusion retreat. Data were analysed using linear mixed-effects models. We failed to support the Compensation Hypothesis, with dreams evidencing fewer social interactions during seclusion. The Strengthening Hypothesis was supported, with more familiar characters present in seclusion dreams. Dream social interactions maintained the Sociality Bias even under seclusion. Additionally, REM sleep increased during seclusion, coinciding with previous literature and tentatively supporting the proposed attachment function for social REM sleep. 

Study Objectives: Growing interest in monitoring sleep and well-being has created a market for consumer home sleep monitoring devices. Additionally, sleep disorder diagnostics, and sleep and dream research would benefit from reliable and valid home sleep monitoring devices. Yet, majority of currently available home sleep monitoring devices lack validation. In this study, the sleep parameter assessment accuracy of Beddit Sleep Tracker (BST), an unobtrusive and non-wearable sleep monitoring device based on ballistocardiography, was evaluated by comparing it with polysomnography (PSG) measures. We measured total sleep time (TST), sleep onset latency (SOL), wake after sleep onset (WASO), and sleep efficiency (SE). Additionally, we examined whether BST can differentiate sleep stages. Methods: We performed sleep studies simultaneously with PSG and BST in ten healthy young adults (5 female/5 male) during two non-consecutive nights in a sleep laboratory. Results: BST was able to distinguish SOL with some accuracy. However, it underestimated WASO and thus overestimated TST and SE. Also, it failed to discriminate between non-rapid eye movement sleep stages and did not detect the rapid eye movement sleep stage. Conclusions: These findings indicate that BST is not a valid device to monitor sleep. Consumers should be careful in interpreting the conclusions on sleep quality and efficiency provided by the device.

Social Simulation Theory (SST) considers the function of dreaming to be the simulation of social events. The Sociality Bias and the Strengthening hypotheses of SST were tested. Social Content Scale (SCS) was developed to quantify social events. Additionally, we attempted to replicate a previous finding (McNamara et al., 2005, Psychological Science) of REM dreams as predisposed to aggressive, and NREM dreams to prosocial interactions. Further, we investigated the frequency and quality of interactions in late vs early REM and NREM dreams. Data consisted of wake, REM and NREM home dream reports (N = 232, 116, 116, respectively) from 15 students. Dreams overrepresented social events compared to wake reports, supporting the Sociality Bias hypothesis. However, the Strengthening Hypothesis was not supported. We weren't able to replicate the McNamara et al. finding, and no time of night effect was found. While SST gained partial support, further research on social contents in dreams is required. © 2019 Elsevier Inc.