Consolidative mechanisms of emotional processing in REM sleep and PTSD

The Dream Experience and Its Relationship with Morning Mood in Adolescents Hospitalized after a Suicide Attempt

Suicidality in adolescents has been associated with emotional distress, stressful life events, relationship issues, and nightmares to name a few. This study explored the actual dream content and the mood at pre-sleep, during a reported dream, and in the morning in 33 adolescents admitted to the hospital on account of a suicide attempt. In all aspects, hospitalized adolescents were compared to 33 matched adolescents who had followed the same protocol. In accordance with the Continuity and the Threat Simulation theories of dream formation, it was hypothesized that the waking-life experiences of suicidal adolescents would transpire in both dream mood and content as well as in the frequency of nightmares. Dreams were analyzed by independent judges using traditional dream content scales, including for the presence of negative and destructive themes and types of interpersonal relationships. As predicted, more suicidal adolescents experienced frequent nightmares, which was significant. A higher negative mood at pre-sleep, within dreams, and at post-sleep was also observed. Furthermore, their dreams contained a higher prevalence of destructive themes and failures, as well as self-directed and death-resulting aggressions. Regression analyses indicated that morning mood was most accurately predicted by positive and negative dream mood in the normative adolescents, whereas only negative dream mood appeared to predict subsequent waking affect in suicidal participants. Our results underline the valuable potential of implementing nightmare-reducing therapies in the presence of suicidal adolescents who suffer from frequent nightmares.

A REM-active basal ganglia circuit that regulates anxiety

Rapid eye movement (REM) sleep has been hypothesized to promote emotional resilience, but any neuronal circuits mediating this have not been identified. We find that in mice, somatostatin (Som) neurons in the entopeduncular nucleus (EPSom)/internal globus pallidus are predominantly active during REM sleep. This unique REM activity is both necessary and sufficient for maintaining normal REM sleep. Inhibiting or exciting EPSom neurons reduced or increased REM sleep duration, respectively. Activation of the sole downstream target of EPSom neurons, Vglut2 cells in the lateral habenula (LHb), increased sleep via the ventral tegmental area (VTA). A simple chemogenetic scheme to periodically inhibit the LHb over 4 days selectively removed a significant amount of cumulative REM sleep. Chronic, but not acute, REM reduction correlated with mice becoming anxious and more sensitive to aversive stimuli. Therefore, we suggest that cumulative REM sleep, in part generated by the EP → LHb → VTA circuit identified here, could contribute to stabilizing reactions to habitual aversive stimuli.

The effect of REM-sleep disruption on affective processing: A systematic review of human and animal experimental studies

Evidence on the importance of rapid-eye-movement sleep (REMS) in processing emotions is accumulating. The focus of this systematic review is the outcomes of experimental REMS deprivation (REMSD), which is the most common method in animal models and human studies on REMSD. This review revealed that variations in the applied REMSD methods were substantial. Animal models used longer deprivation protocols compared with studies in humans, which mostly reported acute deprivation effects after one night. Studies on animal models showed that REMSD causes aggressive behavior, increased pain sensitivity, reduced sexual behavior, and compromised consolidation of fear memories. Animal models also revealed that REMSD during critical developmental periods elicits lasting consequences on affective-related behavior. The few human studies revealed increases in pain sensitivity and suggest stronger consolidation of emotional memories after REMSD. As pharmacological interventions (such as selective serotonin reuptake inhibitors [SSRIs]) may suppress REMS for long periods, there is a clear gap in knowledge regarding the effects and mechanisms of chronic REMS suppression in humans.

Chronic insomnia, REM sleep instability and emotional dysregulation: A pathway to anxiety and depression?

The world-wide prevalence of insomnia disorder reaches up to 10% of the adult population. Women are more often afflicted than men, and insomnia disorder is a risk factor for somatic and mental illness, especially depression and anxiety disorders. Persistent hyperarousals at the cognitive, emotional, cortical and/or physiological levels are central to most theories regarding the pathophysiology of insomnia. Of the defining features of insomnia disorder, the discrepancy between minor objective polysomnographic alterations of sleep continuity and substantive subjective impairment in insomnia disorder remains enigmatic. Microstructural alterations, especially in rapid eye movement sleep ("rapid eye movement sleep instability"), might explain this mismatch between subjective and objective findings. As rapid eye movement sleep represents the most highly aroused brain state during sleep, it might be particularly prone to fragmentation in individuals with persistent hyperarousal. In consequence, mentation during rapid eye movement sleep may be toned more as conscious-like wake experience, reflecting pre-sleep concerns. It is suggested that this instability of rapid eye movement sleep is involved in the mismatch between subjective and objective measures of sleep in insomnia disorder. Furthermore, as rapid eye movement sleep has been linked in previous works to emotional processing, rapid eye movement sleep instability could play a central role in the close association between insomnia and depressive and anxiety disorders.

The importance of REM sleep fragmentation in the effects of stress on sleep: Perspectives from preclinical studies

Psychological stress poses a risk for sleep disturbances. Importantly, trauma-exposed individuals who develop posttraumatic stress disorder (PTSD) frequently report insomnia and recurrent nightmares. Clinical studies have provided insight into the mechanisms of these sleep disturbances. We review polysomnographic findings in PTSD and identify analogous measures that have been made in animal models of PTSD. There is a rich empirical and theoretical literature on rapid eye movement sleep (REMS) substrates of insomnia and nightmares, with an emphasis on REMS fragmentation. For future investigations of stress-induced sleep changes, we recommend a focus on tonic, phasic and other microarchitectural REMS measures. Power spectral density analysis of the sleep EEG should also be utilized. Animal models with high construct validity can provide insight into gender and time following stressor exposure as moderating variables. Ultimately, preclinical studies with translational potential will lead to improved treatment for stress-related sleep disturbances.

To "feel" better, sleep on it!

Emotional memories are consolidated during REM sleep.

The Ponto-Geniculo-Occipital (PGO) Waves in Dreaming: An Overview

Rapid eye movement (REM) sleep is the main sleep correlate of dreaming. Ponto-geniculo-occipital (PGO) waves are a signature of REM sleep. They represent the physiological mechanism of REM sleep that specifically limits the processing of external information. PGO waves look just like a message sent from the pons to the lateral geniculate nucleus of the visual thalamus, the occipital cortex, and other areas of the brain. The dedicated visual pathway of PGO waves can be interpreted by the brain as visual information, leading to the visual hallucinosis of dreams. PGO waves are considered to be both a reflection of REM sleep brain activity and causal to dreams due to their stimulation of the cortex. In this review, we summarize the role of PGO waves in potential neural circuits of two major theories, i.e., (1) dreams are generated by the activation of neural activity in the brainstem; (2) PGO waves signaling to the cortex. In addition, the potential physiological functions during REM sleep dreams, such as memory consolidation, unlearning, and brain development and plasticity and mood regulation, are discussed. It is hoped that our review will support and encourage research into the phenomenon of human PGO waves and their possible functions in dreaming.

From childhood adversity to latent stress vulnerability in adulthood: the mediating roles of sleep disturbances and HPA axis dysfunction

Childhood adversity is a prominent predisposing risk factor for latent stress vulnerability, expressed as an elevated likelihood of developing stress-related psychopathology upon subsequent exposure to trauma in adulthood. Sleep disturbances have emerged as one of the most pronounced maladaptive behavioral outcomes of childhood adversity and are also a highly prevalent core feature of stress-related psychopathology, including post-traumatic stress disorder (PTSD). After reviewing the extensive literature supporting these claims, the current review addresses the notion that childhood adversity-induced sleep disturbances may play a causal role in elevating individuals' stress vulnerability in adulthood. Corroborating this, sleep disturbances that predate adult trauma exposure have been associated with an increased likelihood of developing stress-related psychopathology post-exposure. Furthermore, novel empirical evidence suggests that sleep disturbances, including irregularity of the sleep-wake cycle, mediate the link between childhood adversity and stress vulnerability in adulthood. We also discuss cognitive and behavioral mechanisms through which such a cascade may evolve, highlighting the putative role of impaired memory consolidation and fear extinction. Next, we present evidence to support the contribution of the hypothalamic-pituitary-adrenal (HPA) axis to these associations, stemming from its critical role in stress and sleep regulatory pathways. Childhood adversity may yield bi-directional effects within the HPA stress and sleep axes in which sleep disturbances and HPA axis dysfunction reinforce each other, leading to elevated stress vulnerability. To conclude, we postulate a conceptual path model from childhood adversity to latent stress vulnerability in adulthood and discuss the potential clinical implications of these notions, while highlighting directions for future research.

Dexmedetomidine prevents spatial learning and memory impairment induced by chronic REM sleep deprivation in rats

The study was attempted to investigate the effect on and mechanisms of action of dexmedetomidine with regard to learning and memory impairment in rats with chronic rapid eye movement (REM) sleep deprivation. A total of 50 male Sprague Dawley rats were randomly divided into five groups. Modified multiple platform method was conducted to cause the sleep deprivation of rats. Dexmedetomidine and midazolam were administered by intraperitoneal injection. Learning and memory ability was assessed through Morris water maze. Morphological changes of rat hippocampal neurons and synaptic were detected by transmission electron microscope and Golgi staining. The gene expression in hippocampus of each group was detected by RNA-seq and verified by RT-PCR and western blot. REM Sleep-deprived rats exhibited spatial learning and memory deficits. Furthermore, there was decreased density of synaptic spinous in the hippocampal CA1 region of the sleep deprivation group compared with the control. Additionally, transmission electron microscopy showed that the synaptic gaps of hippocampal neurons in REM sleep deprivation group were loose and fuzzy. Interestingly, dexmedetomidine treatment normalized these events to control levels following REM sleep deprivation. Molecular biological methods showed that Alox15 expression increased significantly after REM sleep deprivation as compared to control, while dexmedetomidine administration reversed the expression of Alox15. Dexmedetomidine alleviated the spatial learning and memory dysfunction induced with chronic REM sleep deprivation in rats. This protective effect may be related to the down-regulation of Alox15 expression and thereby the enhancement of synaptic structural plasticity in the hippocampal CA1 area of rats.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41105-023-00450-8.

The temporal structure of REM sleep shows minute-scale fluctuations across brain and body in mice and humans

Rapid eye movement sleep (REM) is believed to have a binary temporal structure with "phasic" and "tonic" microstates, characterized by motoric activity versus quiescence, respectively. However, we observed in mice that the frequency of theta activity (a marker of rodent REM) fluctuates in a nonbinary fashion, with the extremes of that fluctuation correlating with phasic-type and tonic-type facial motricity. Thus, phasic and tonic REM may instead represent ends of a continuum. These cycles of brain physiology and facial movement occurred at 0.01 to 0.06 Hz, or infraslow frequencies, and affected cross-frequency coupling and neuronal activity in the neocortex, suggesting network functional impact. We then analyzed human data and observed that humans also demonstrate nonbinary phasic/tonic microstates, with continuous 0.01 to 0.04-Hz respiratory rate cycles matching the incidence of eye movements. These fundamental properties of REM can yield insights into our understanding of sleep health.

Regulation of dendritic spines in the amygdala following sleep deprivation

The amygdala is a hub of emotional circuits involved in the regulation of cognitive and emotional behaviors and its critically involved in emotional reactivity, stress regulation, and fear memory. Growing evidence suggests that the amygdala plays a key role in the consolidation of emotional memories during sleep. Neuroimaging studies demonstrated that the amygdala is selectively and highly activated during rapid eye movement sleep (REM) and sleep deprivation induces emotional instability and dysregulation of the emotional learning process. Regulation of dendritic spines during sleep represents a morphological correlate of memory consolidation. Several studies indicate that dendritic spines are remodeled during sleep, with evidence for broad synaptic downscaling and selective synaptic upscaling in several cortical areas and the hippocampus. Currently, there is a lack of information regarding the regulation of dendritic spines in the amygdala during sleep. In the present work, we investigated the effect of 5 h of sleep deprivation on dendritic spines in the mouse amygdala. Our data demonstrate that sleep deprivation results in differential dendritic spine changes depending on both the amygdala subregions and the morphological subtypes of dendritic spines. We observed decreased density of mushroom spines in the basolateral amygdala of sleep deprived mice, together with increased neck length and decreased surface area and volume. In contrast, we observed greater densities of stubby spines in sleep deprived mice in the central amygdala, indicating that downscaling selectively occurs in this spine type. Greater neck diameters for thin spines in the lateral and basolateral nuclei of sleep deprived mice, and decreases in surface area and volume for mushroom spines in the basolateral amygdala compared to increases in the cental amygdala provide further support for spine type-selective synaptic downscaling in these areas during sleep. Our findings suggest that sleep promotes synaptic upscaling of mushroom spines in the basolateral amygdala, and downscaling of selective spine types in the lateral and central amygdala. In addition, we observed decreased density of phosphorylated cofilin immunoreactive and growth hormone immunoreactive cells in the amygdala of sleep deprived mice, providing further support for upscaling of dendritic spines during sleep. Overall, our findings point to region-and spine type-specific changes in dendritic spines during sleep in the amygdala, which may contribute to consolidation of emotional memories during sleep.

Machine Learning Identifies a Rat Model of Parkinson's Disease via Sleep-Wake Electroencephalogram

Alpha-synuclein induced degeneration of the midbrain substantia nigra pars compact (SNc) dopaminergic neurons causes Parkinson's disease (PD). Rodent studies demonstrate that nigrostriatal dopamine stimulates pallidal neurons which, via the topographical pallidocortical pathway, regulate cortical activity and functions. We hypothesize that nigrostriatal dopamine acting at the basal ganglia regulates cortical activity in sleep and wake state, and its depletion systemically alters electroencephalogram (EEG) across frequencies during sleep-wake state. Compared to control rats, 6-hydroxydopamine induced selective SNc lesions increased overall EEG power (positive synchronization) across 0.5-60 Hz during wake, NREM (non-rapid eye movement) sleep, and REM sleep. Application of machine learning (ML) to seven EEG features computed at a single or combined spectral bands during sleep-wake differentiated SNc lesions from controls at high accuracy. ML algorithms construct a model based on empirical data to make predictions on subsequent data. The accuracy of the predictive results indicate that nigrostriatal dopamine depletion increases global EEG spectral synchronization in wake, NREM sleep, and REM sleep. The EEG changes can be exploited by ML to identify SNc lesions at a high accuracy.

Pre-sleep affect predicts subsequent REM frontal theta in nonlinear fashion

Pre-sleep affect is thought to influence sleep, but associations with both sleep architecture and the electroencephalographic (EEG) power spectrum are mixed. In this pre-registered study, we assessed negative valence and arousal 1 h pre-sleep in 52 adults drawn from the community, then recorded one night of polysomnography (PSG) in participants' own homes. Pre-sleep affect was not associated with nonrapid eye movement (NREM) or rapid eye movement (REM) sleep architecture parameters, but we did observe inverted U-shaped relationships between both negative valence and arousal and REM frontal theta power, such that theta power was highest at moderate negative valence and arousal, and lowest at either affective extreme. When entered into a model together, both valence and arousal accounted for independent variance. Secondary analyses revealed a similar quadratic association with pre-sleep positive valence, suggesting a nonspecific effect of pre-sleep valence on REM frontal theta. Robustness checks confirmed that effects were not explained by homeostatic sleep pressure or sleep timing. Our results suggest that mixed findings in the literature may reflect different ends of a quadratic function, underscoring the importance of assessing how different components of pre-sleep affect relate to sleep.

Emotion dysregulation mediates the association between acute sleep disturbance and later posttraumatic stress symptoms in trauma exposed adults

Background: Sleep disturbance is common within days to weeks following a traumatic event and has been associated with emotion dysregulation, a strong risk factor for PTSD development. This study aims to examine if emotion dysregulation mediates the relationship between early post-trauma sleep disturbance and subsequent PTSD symptom severity.Methods: Adult participants (n = 125) completed questionnaires regarding sleep disturbance (via Pittsburgh Sleep Quality Index Addendum; PSQI-A) and emotion dysregulation (via Difficulties in Emotion Regulation Scale; DERS) within 2 weeks after exposure to traumatic events.Results: PTSD symptom severity was assessed with PTSD Checklist for DSM-5 (PCL-5) at 3-month follow-up. There were strong correlations between PSQI-A, DERS, and PCL-5 (r ranges between .38 and .45). Mediation analysis further revealed significant indirect effects of overall emotion regulation difficulties in the relationship between sleep disturbance at 2 weeks and PTSD symptom severity at 3 months (B = .372, SE = .136, 95% CI: [.128, .655]). Importantly, limited access to emotion regulation strategies emerged as the single, significant indirect effect in this relationship (B = .465, SE = .204, 95% CI [.127, .910]) while modelling DERS subscales as multiple parallel mediators.Conclusions: Early post-trauma sleep disturbance is associated with PTSD symptoms over months, and acute emotion dysregulation explains part of this association. Those with limited emotion regulation strategies are at particular risk of developing PTSD symptoms. Early interventions focusing on the appropriate strategies for emotion regulation may be crucial for trauma-exposed individuals.

Actigraphic sleep monitoring in patients with post-traumatic stress disorder (PTSD): A meta-analysis

OBJECTIVE

Sleep disruption is a common complaint among patients with post-traumatic stress disorder (PTSD). Modern technology of activity monitoring (actigraphy) enables extended, objective, unobtrusive recording and measuring of daytime and nighttime activity. We conducted a meta-analysis to investigate the actigraphic sleep patterns in PTSD compared with healthy controls.

METHODS

We searched through seven electronic databases from inception to July 2022. Only case-control studies comparing rest-activity variables measured by actigraphy devices between clinically diagnosed PTSD patients and healthy individuals were included.

RESULTS

We identified 12 eligible studies comparing 323 PTSD patients and 416 healthy controls. Using a random-effects model, we showed that PTSD patients have significantly lower sleep efficiency (SMD: -0.26, 95 % CI = -0.51 to -0.004, p < .05, I² = 29.31 %), more fragmented sleep (SMD: 0.52, 95 % CI = 0.17 to 0.87, p < .01, I² = 0 %), and longer time in bed (SMD: 0.41, 95 % CI = 0.07 to 0.74, p < .05, I² = 0 %) compared to healthy controls.

LIMITATIONS

This study included a limited number of studies. Publication bias was not examined on all variables, which could lead to an overestimation of effect size. Four studies involved veterans, which likely differ from civilians regarding traumatic exposure.

CONCLUSION

This meta-analytic review highlighted a pattern of sleep disturbances in PTSD patients compared with non-PTSD individuals. High-quality, large-scale studies are necessary to draw a definitive conclusion regarding the distinctive sleep profile in PTSD. Future research can pay attention to sleep-specific mechanisms underlying PTSD and explore the momentary interactions between sleep-wake variables.

GABAergic neurons in the rostromedial tegmental nucleus are essential for rapid eye movement sleep suppression

Rapid eye movement (REM) sleep disturbances are prevalent in various psychiatric disorders. However, the neural circuits that regulate REM sleep remain poorly understood. Here, we found that in male mice, optogenetic activation of rostromedial tegmental nucleus (RMTg) GABAergic neurons immediately converted REM sleep to arousal and then initiated non-REM (NREM) sleep. Conversely, laser-mediated inactivation completely converted NREM to REM sleep and prolonged REM sleep duration. The activity of RMTg GABAergic neurons increased to a high discharge level at the termination of REM sleep. RMTg GABAergic neurons directly converted REM sleep to wakefulness and NREM sleep via inhibitory projections to the laterodorsal tegmentum (LDT) and lateral hypothalamus (LH), respectively. Furthermore, LDT glutamatergic neurons were responsible for the REM sleep-wake transitions following photostimulation of the RMTg^GABA-LDT circuit. Thus, RMTg GABAergic neurons are essential for suppressing the induction and maintenance of REM sleep.

Is paradoxical sleep setting up innate and acquired complex sensorimotor and adaptive behaviours?: A proposed function based on literature review

We summarize here the progress in identifying the neuronal network as well as the function of paradoxical sleep and the gaps of knowledge that should be filled in priority. The core system generating paradoxical sleep localized in the brainstem is now well identified, and the next step is to clarify the role of the forebrain in particular that of the hypothalamus including the melanin-concentrating hormone neurons and of the basolateral amygdala. We discuss these two options, and also the discovery that cortical activation during paradoxical sleep is restricted to a few limbic cortices activated by the lateral supramammillary nucleus and the claustrum. Such activation nicely supports the findings recently obtained showing that neuronal reactivation occurs during paradoxical sleep in these structures, and induces both memory consolidation of important memory and forgetting of less relevant ones. The question that still remains to be answered is whether paradoxical sleep is playing more crucial roles in processing emotional and procedural than other types of memories. One attractive hypothesis is that paradoxical sleep is responsible for erasing negative emotional memories, and that this function is not properly functioning in depressed patients. On the other hand, the presence of a muscle atonia during paradoxical sleep is in favour of a role in procedural memory as new types of motor behaviours can be tried without harm during the state. In a way, it also fits with the proposed role of paradoxical sleep in setting up the sensorimotor system during development.

Paradoxical somatodendritic decoupling supports cortical plasticity during REM sleep

Rapid eye movement (REM) sleep is associated with the consolidation of emotional memories. Yet, the underlying neocortical circuits and synaptic mechanisms remain unclear. We found that REM sleep is associated with a somatodendritic decoupling in pyramidal neurons of the prefrontal cortex. This decoupling reflects a shift of inhibitory balance between parvalbumin neuron-mediated somatic inhibition and vasoactive intestinal peptide-mediated dendritic disinhibition, mostly driven by neurons from the central medial thalamus. REM-specific optogenetic suppression of dendritic activity led to a loss of danger-versus-safety discrimination during associative learning and a lack of synaptic plasticity, whereas optogenetic release of somatic inhibition resulted in enhanced discrimination and synaptic potentiation. Somatodendritic decoupling during REM sleep promotes opposite synaptic plasticity mechanisms that optimize emotional responses to future behavioral stressors.

A Narrative Review of the Association between Post-Traumatic Stress Disorder and Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) and post-traumatic stress disorder (PTSD) are often co-morbid with implications for disease severity and treatment outcomes. OSA prevalence is higher in PTSD sufferers than in the general population, with a likely bidirectional effect of the two illnesses. There is substantial evidence to support the role that disturbed sleep may play in the pathophysiology of PTSD. Sleep disturbance associated with OSA may interfere with normal rapid eye movement (REM) functioning and thus worsen nightmares and sleep-related movements. Conversely, hyperarousal and hypervigilance symptoms of PTSD may lower the arousal threshold and thus increase the frequency of sleep fragmentation related to obstructive events. Treating OSA not only improves OSA symptoms, but also nightmares and daytime symptoms of PTSD. Evidence suggests that positive airway pressure (PAP) therapy reduces PTSD symptoms in a dose-dependent fashion, but also presents challenges to tolerance in the PTSD population. Alternative OSA treatments may be better tolerated and effective for improving both OSA and PTSD. Further research avenues will be introduced as we seek a better understanding of this complex relationship.

Louis EK. Abnormal rapid eye movement sleep atonia control in chronic post-traumatic stress disorder

STUDY OBJECTIVES

Post-traumatic stress disorder (PTSD) and rapid eye movement (REM) sleep behavior disorder (RBD) share some common features including prominent nightmares and sleep disturbances. We aimed to comparatively analyze REM sleep without atonia (RSWA) between patients with chronic PTSD with and without dream enactment behavior (DEB), isolated RBD (iRBD), and controls.

METHODS

In this retrospective study, we comparatively analyzed 18 PTSD with DEB (PTSD+DEB), 18 PTSD without DEB, 15 iRBD, and 51 controls matched for age and sex. We reviewed medical records to determine PTSD clinical features and quantitatively analyzed RSWA. We used nonparametric analyses to compare clinical and polysomnographic features.

RESULTS

PTSD patients, both with and without DEB, had significantly higher RSWA than controls (all p < .025, excepting submentalis phasic duration in PTSD+DEB). Most RSWA measures were also higher in PTSD+DEB than in PTSD without DEB patients (all p < .025).

CONCLUSIONS

PTSD patients have higher RSWA than controls, whether DEB is present or not, indicating that REM sleep atonia control is abnormal in chronic PTSD. Further prospective studies are needed to determine whether neurodegenerative risk and disease markers similar to RBD might occur in PTSD patients.

Cannabinoids: Revealing their complexity and role in central networks of fear and anxiety

The first aim of the present review is to provide an in-depth description of the cannabinoids and their known effects at various neuronal receptors. It reveals that cannabinoids are highly diverse, and recent work has highlighted that their effects on the central nervous system (CNS) are surprisingly more complex than previously recognized. Cannabinoid-sensitive receptors are widely distributed throughout the CNS where they act as primary modulators of neurotransmission. Secondly, we examine the role of cannabinoid receptors at key brain sites in the control of fear and anxiety. While our understanding of how cannabinoids specifically modulate these networks is mired by their complex interactions and diversity, a plausible framework(s) for their effects is proposed. Finally, we highlight some important knowledge gaps in our understanding of the mechanism(s) responsible for their effects on fear and anxiety in animal models and their use as therapeutic targets in humans. This is particularly important for our understanding of the phytocannabinoids used as novel clinical interventions.

The Many Faces of Sleep Disorders in Post-Traumatic Stress Disorder: An Update on Clinical Features and Treatment

Sleep disorders and nightmares are core symptoms of post-traumatic stress disorder (PTSD). The relationship seems to be bidirectional, and persistent disturbed sleep may influence the course of the disorder. With regard to sleep quality, insomnia and nocturnal anxiety symptoms, as well as nightmares and stressful dreams, are the most prominent sleep symptoms. Polysomnographic measurements reveal alterations of the sleep architecture and fragmentation of rapid eye movement sleep. In addition, sleep disorders, such as sleep-related breathing disorders and parasomnias are frequent comorbid conditions. The complex etiology and symptomatology of trauma-related sleep disorders with frequent psychiatric comorbidity require the application of multimodal treatment concepts, including psychological and pharmacological interventions. However, there is little empirical evidence on the effectiveness of long-term drug treatment for insomnia and nightmares. For nondrug interventions, challenges arise from the current lack of PTSD-treatment concepts integrating sleep- and trauma-focused therapies. Effective therapy for sleep disturbances may consequently also improve well-being during the day and probably even the course of PTSD. Whether early sleep interventions exert a preventive effect on the development of PTSD remains to be clarified in future studies.

Excessive daytime sleepiness is associated with altered gene expression in military personnel and veterans with posttraumatic stress disorder: an RNA sequencing study

STUDY OBJECTIVES

Posttraumatic stress disorder (PTSD) is a common condition for military personnel and veterans. PTSD has been shown to impact gene expression, however, to date no study has examined comorbid conditions which may also impact gene expression, for example, excessive daytime sleepiness (EDS). As such, this study sought to examine gene expression using RNA sequencing across three group comparisons of military personnel and veterans: (1) PTSD with EDS (PTSDwEDS) versus PTSD without EDS (PTSDw/outEDS), (2) Controls (no PTSD or EDS) versus PTSDwEDS, and (3) Controls versus PTSDw/outEDS.

METHODS

We performed experimental RNA-seq using Illumina's HiSeq 2500 Sequencing System. We also used Ingenuity Pathway Analysis (IPA), a bioinformatics application, to identify gene pathways and networks which may be disrupted.

RESULTS

There were only two genes that were significantly dysregulated between the Controls and PTSDw/outEDS, therefore IPA analysis was not conducted. However, comparisons revealed that there was significant gene dysregulation between Controls and the PTSDwEDS (251 genes), and the PTSDwEDS versus the PTSDw/outEDS (1,873 genes) groups. Four candidate networks were identified via the IPA software for analysis. Significantly dysregulated genes across the four candidate networks were associated with sleep and circadian function, metabolism, mitochondrial production and function, ubiquitination, and the glutamate system.

CONCLUSIONS

These results suggest that PTSD with concurrent EDS is associated with gene dysregulation. This dysregulation may present additional biological and health consequences for these military personnel and veterans. Further research, to track these gene changes over time and to determine the cause of the EDS reported, is vital.

MicroRNAs in Basolateral Amygdala Associated with Stress and Fear Memories Regulate Rapid Eye Movement Sleep in Rats

Stress-related sleep disturbances are distressing clinical symptoms in posttraumatic stress disorder patients. Intensely stressful events and their memories change rapid eye movement (REM) sleep in animal models. REM sleep varies with individual differences of stress resilience or vulnerability. The basolateral amygdala (BLA) is a primary mediator of the effects of stress and fear memories on sleep. However, the molecular mechanisms in BLA regulating the effects of fear conditioning, shock training (ST) and context re-exposure (CTX) on REM sleep are not well known. MicroRNAs (miRNAs) are small, non-coding RNAs and posttranscriptional gene regulators of diverse biological processes. The aim of this study is to investigate ST- and CTX-altered miRNAs in the BLA of resilience and vulnerable animals and on REM sleep regulation. MiRNAs expression profiles in BLA were generated following ST and CTX using the Taqman Low Density rodent microRNA array. The altered BLA miRNAs expression and REM sleep reduction observed in ST and CTX vulnerable animals. AntagomiR-221 microinjection into BLA for one of the upregulated miRNAs, miR-221 in BLA, attenuated the REM sleep reduction. This study suggests that miRNAs in the BLA may play a significant role in mediating the effects of stress and fear memories on REM sleep.

Chronic sleep fragmentation enhances habenula cholinergic neural activity

Sleep is essential to emotional health. Sleep disturbance, particularly REM sleep disturbance, profoundly impacts emotion regulation, but the underlying neural mechanisms remain elusive. Here we show that chronic REM sleep disturbance, achieved in mice by chronic sleep fragmentation (SF), enhanced neural activity in the medial habenula (mHb), a brain region increasingly implicated in negative affect. Specifically, after a 5-day SF procedure that selectively fragmented REM sleep, cholinergic output neurons (ChNs) in the mHb exhibited increased spontaneous firing rate and enhanced firing regularity in brain slices. The SF-induced firing changes remained intact upon inhibition of glutamate, GABA, acetylcholine, and histamine receptors, suggesting cell-autonomous mechanisms independent of synaptic transmissions. Moreover, the SF-induced hyperactivity was not because of enhanced intrinsic membrane excitability, but was accompanied by depolarized resting membrane potential in mHb ChNs. Furthermore, inhibition of TASK-3 (KCNK9) channels, a subtype of two-pore domain K⁺ channels, mimicked the SF effects by increasing the firing rate and regularity, as well as depolarizing the resting membrane potential in mHb ChNs in control-sleep mice. These effects of TASK-3 inhibition were absent in SF mice, suggesting reduced TASK-3 activity following SF. By contrast, inhibition of small-conductance Ca²⁺-activated K⁺ (SK) channels did not produce similar effects. Thus, SF compromised TASK-3 function in mHb ChNs, which likely led to depolarized resting membrane potential and increased spontaneous firing. These results not only demonstrate that selective REM sleep disturbance leads to hyperactivity of mHb ChNs, but also identify a key molecular substrate through which REM sleep disturbance may alter affect regulation.

Does Sleep Selectively Strengthen Certain Memories Over Others Based on Emotion and Perceived Future Relevance?

Sleep has been found to have a beneficial effect on memory consolidation. It has furthermore frequently been suggested that sleep does not strengthen all memories equally. The first aim of this review paper was to examine whether sleep selectively strengthens emotional declarative memories more than neutral ones. We examined this first by reviewing the literature focusing on sleep/wake contrasts, and then the literature on whether any specific factors during sleep preferentially benefit emotional memories, with a special focus on the often-suggested claim that rapid eye movement sleep primarily consolidates emotional memories. A second aim was to examine if sleep preferentially benefits memories based on other cues of future relevance such as reward, test-expectancy or different instructions during encoding. Once again, we first focused on studies comparing sleep and wake groups, and then on studies examining the contributions of specific factors during sleep (for each future relevance paradigm, respectively). The review revealed that although some support exists that sleep is more beneficial for certain kinds of memories based on emotion or other cues of future relevance, the majority of studies does not support such an effect. Regarding specific factors during sleep, our review revealed that no sleep variable has reliably been found to be specifically associated with the consolidation of certain kinds of memories over others based on emotion or other cues of future relevance.

Sleep architecture and homeostasis in children with epilepsy: a neurodevelopmental perspective

Although the influence of sleep on epilepsy has long been recognized, this relationship has yet to be fully exploited to benefit patients. The past decade has seen significant advances in understanding paediatric sleep, providing a framework by which to properly evaluate the sleep of children with epilepsy, which itself has been subject to increasing scrutiny. The role of sleep in learning and the potential for interictal discharges to disrupt sleep-related memory consolidation provide a novel perspective for understanding the association of childhood epilepsy with a high rate of intellectual disability. In this review, I outline the evolution of sleep duration, architecture, and homeostasis across childhood, relating this to the development of cognitive functions. I describe how these may be disrupted or preserved in children with epilepsy; in particular, collating data from polysomnography. Finally, I explore how sleep may, in the future, be modulated to improve cognitive outcome in these patients. WHAT THIS PAPER ADDS: Children with epilepsy have less rapid eye movement sleep than controls, but this improves with seizure cessation. Deep or slow-wave sleep is highly conserved in children with epilepsy. Sleep homeostasis may be disrupted either at a local or global level by the presence of interictal epileptiform discharges.

Mental Violence: The COVID-19 Nightmare

The year 2020 has generated profound changes in personal and working relations, and in dreams of millions of people worldwide. The aim of this study was to investigate the frequency and content of nightmares during the COVID-19 pandemic in Brazil, evaluating its associations with sociodemographic, occupational, and clinical factors. Cross-sectional exploratory study, including 1,057 participants who responded to an online survey about mental violence and nightmares during the pandemic, between May 25 and June 1, 2020. A descriptive analysis of the results was done to obtain frequency tables. McNemar's non-parametric test was used to compare the frequency of nightmares before and after the pandemic, and logistic regression models, to identify factors most strongly associated with the pandemic nightmares. Participants were from 21 Brazilian states, with a mean age of 38 ± 14 years, and 78% women. Half of them (n = 529) reported at least one nightmare episode during the pandemic, and 32.9% (n = 348) described a pandemic content. There was nearly a 3-fold increase in the occurrence of nightmares "once a week or more" during the pandemic, 9% before vs. 25% after. Prior psychiatric care, suicidal ideation, sleep medication, increased pandemic alcohol consumption, perceiving high risk of contamination, being woman, and of younger age were factors associated with having nightmares during the pandemic. Prior psychiatric care, sleep medication, and age remained significant after excluding participants without nightmares and comparing between individuals with and without a pandemic content. We conclude the COVID-19 pandemic has affected people's dreams. The increase in the frequency of nightmares, their pandemic content, and association with previous conditions are a concerning public mental health issue and should be taken into consideration by authorities and policy makers.

Sleep in posttraumatic stress disorder: A systematic review and meta-analysis of polysomnographic findings

Polysomnographic studies have been performed to examine sleep abnormalities in posttraumatic stress disorder (PTSD), but clear associations between PTSD and sleep disturbances have not been established. A systematic review of the evidence examining the polysomnographic changes in PTSD patients compared with controls was conducted using MEDLINE, EMBASE, All EBM databases, PsycINFO, and CINAHL databases. Meta-analysis was undertaken where possible. The searches identified 34 studies, 31 of which were appropriate for meta-analysis. Pooled results indicated decreased total sleep time, slow wave sleep and sleep efficiency, and increased wake time after sleep onset in PTSD patients compared with healthy controls. PTSD severity was associated with decreased sleep efficiency and slow wave sleep percentage. Rapid eye movement (REM) sleep percentage was significantly decreased in PTSD patients compared with controls in studies including participants with mean age below 30 y, but not in studies with other mean age groups (30-40 y and >40 y). Our study shows that polysomnographic abnormalities are present in PTSD. Sex, age, PTSD severity, type of controls, medication status, adaptation night, polysomnographic scoring rules and study location are several of the demographic, clinical and methodological factors that contribute to heterogeneity between studies.

Recognizing Poor Sleep Quality Factors During Oral Health Evaluations

Oral health practitioners routinely perform oral health assessments for the dental patient to determine if oral disease is present. Systemic health is often a contributor to oral health concerns. One area in particular that has a direct effect on oral structures and oral health is poor sleep quality and open mouth breathing. Sleep is a fundamental process of the human body, which regulates core biological functions. Sleep quality reflects a person's ability to fall asleep, stay asleep, and enter into the various rejuvenating sleep cycles for the full duration. A person who does not obtain quality sleep can exhibit a wide range of oral, systemic, and cognitive health problems. Obstructive sleep apnea, which historically has been considered an adult male disease, is being recognized more often in women children. Research suggests various oral malformations found in newborns and young children can manifest as obstructive sleep apnea in adults. Oral health professionals are in a position to recognize the relationship between sleep and health, identify sleep quality concerns in relation to oral health assessments, administer sleep quality assessments, and determine appropriate referrals for further sleep quality evaluation.

The Functional Role of Dreaming in Emotional Processes

Dream experience (DE) represents a fascinating condition linked to emotional processes and the human inner world. Although the overlap between REM sleep and dreaming has been overcome, several studies point out that emotional and perceptually vivid contents are more frequent when reported upon awakenings from this sleep stage. Actually, it is well-known that REM sleep plays a pivotal role in the processing of salient and emotional waking-life experiences, strongly contributing to the emotional memory consolidation. In this vein, we highlighted that, to some extent, neuroimaging studies showed that the processes that regulate dreaming and emotional salience in sleep mentation share similar neural substrates of those controlling emotions during wakefulness. Furthermore, the research on EEG correlates of the presence/absence of DE and the results on EEG pattern related to the incorporated memories converged to assign a crucial role of REM theta oscillations in emotional re-processing. In particular, the theta activity is involved in memory processes during REM sleep as well as during the waking state, in line with the continuity hypothesis. Also, the gamma activity seems to be related to emotional processes and dream recall as well as to lucid dreams. Interestingly, similar EEG correlates of DE have been found in clinical samples when nightmares or dreams occur. Research on clinical samples revealed that promoting the rehearsal of frightening contents aimed to change them is a promising method to treat nightmares, and that lucid dreams are associated with an attenuation of nightmares. In this view, DE can defuse emotional traumatic memories when the emotional regulation and the fear extinction mechanisms are compromised by traumatic and frightening events. Finally, dreams could represent a sort of simulation of reality, providing the possibility to create a new scenario with emotional mastery elements to cope with dysphoric items included in nightmares. In addition, it could be hypothesized that the insertion of bizarre items besides traumatic memories might be functional to "impoverish" the negative charge of the experiences.

Modelling posttraumatic stress disorders in animals

Animal models of posttraumatic stress disorder are useful tools to reveal the neurobiological basis of the vulnerability to traumatic events, and to develop new treatment strategies, as well as predicting treatment response contributing to personalized medicine approach. Different models have different construct, face and predictive validity and they model different symptoms of the disease. The most prevalent models are the single prolonged stress, electric foot-shock and predator odor. Freezing as 're-experiencing' in cluster B and startle as 'arousal' in cluster E according to DSM-5 are the most frequently studied parameters; however, several other symptoms related to mood, cognitive and social skills are part of the examinations. Beside behavioral characteristics, symptoms of exaggerated sympathetic activity and hypothalamic-pituitary-adrenocortical axis as well as signs of sleep disturbances are also warranted. Test battery rather than a single test is required to describe a model properly and the results should be interpreted in a comprehensive way, e.g. creating a z-score. Research is shifting to study larger populations and identifying the features of the resilient and vulnerable individuals, which cannot be easily done in humans. Incorporation of the "three hit theory" in animal models may lead to a better animal model of vulnerability and resilience. As women are twice as vulnerable as men, more emphasize should be taken to include female animals. Moreover, hypothesis free testing and big data analysis may help to identify an array of biomarkers instead of a single variable for identification of vulnerability and for the purpose of personalized medicine.

REM sleep fragmentation associated with depressive symptoms and genetic risk for depression in a community-based sample of adolescents

INTRODUCTION

Fragmented REM sleep may impede overnight resolution of distress and increase depressive symptoms. Furthermore, both fragmented REM and depressive symptoms may share a common genetic factor. We explored the associations between REM sleep fragmentation, depressive symptoms, and a polygenic risk score (PRS) for depression among adolescents.

METHODS

About 161 adolescents (mean age 16.9 ± 0.1 years) from a birth cohort underwent a sleep EEG and completed the Beck Depression Inventory-II the same day. We calculated PRSes for depressive symptoms with PRSice 1.25 software using weights from a recent genome-wide association study for dimensions of depressive symptoms (negative emotion, lack of positive emotion and somatic complaints). REM fragmentation in relation to entire REM duration was manually calculated from all REM epochs. REM latency and density were derived using SomnoMedics DOMINO software.

RESULTS

PRSes for somatic complaints and lack of positive emotions were associated with higher REM fragmentation percent. A higher level of depressive symptoms was associated with increased percent of REM fragmentation and higher REM density, independently of the genetic risks. Belonging to the highest decile in depressive symptoms was associated with a 2.9- and 7.6-fold risk of belonging to the highest tertile in REM fragmentation and density. In addition, higher PRS for somatic complaints had an independent, additive effect on increased REM fragmentation.

LIMITATION

A single night's sleep EEG was measured, thus the night-to-night stability of the REM fragmentation-depressive symptom link is unclear.

CONCLUSION

Depressive symptoms and genetic risk score for somatic complaints are independently associated with more fragmented REM sleep. This offers new insights on the quality of sleep and its relation to adolescents' mood.

Abnormal Topology of the Structural Connectome in the Limbic Cortico-Basal-Ganglia Circuit and Default-Mode Network Among Primary Insomnia Patients

Purpose: Primary insomnia (PI) is the second most common mental disorder. However, the topologic alterations in structural brain connectome in patients with PI remain largely unknown. Methods: A total of 44 PI patients and 46 age-, gender-, and education level matched healthy control (HC) participants were recruited in this study. Diffusion tensor imaging (DTI) and resting state MRI were used to construct structural connectome for each participant, and the network parameters were employed by non-parametric permutations to evaluate the significant differences between the two groups. Relationships between abnormal network metrics and clinical characteristics, including the disease duration, the Pittsburgh Sleep Quality Index (PSQI), the Insomnia Severity Index (ISI), the Self-Rating Anxiety Scale (SAS), and the Self-Rating Depression Scale (SDS), were investigated with Spearman's correlation analysis in PI patients. Results: PI patients demonstrated small-world architecture with lower global (P = 0.005) and local (P = 0.035) efficiencies compared with the HC group. The unique hub nodal properties in PI patients were mainly in the right limbic cortico-basal-ganglia circuit. Five disrupted subnetworks in PI patients were observed in the limbic cortico-basal-ganglia circuit and left default-mode networks (DMN) (P < 0.05, NBS corrected). Moreover, most unique hub nodal properties in the right limbic cortico-basal-ganglia circuit were significantly correlated with disease duration, and clinical characteristics (SAS, SDS, ISI scores) in PI processing. Conclusion: These findings suggested the abnormal anatomical network architecture may be closely linked to clinical characteristics in PI. The study provided novel insights into the neural substrates underlying symptoms and neurophysiologic mechanisms of PI.