Rapid Eye Movement Periods Research Articles

Sleepiness and sleepiness perception in patients with Parkinson's disease: a clinical and electrophysiological study.

The main objective of the study was to assess the prevalence, the severity, and the daytime course of excessive daytime sleepiness (EDS) in advanced Parkinson's disease (PD) and to explore how people with PD perceive the degree and onset of their sleepiness during objective sleepiness tests. In addition, the occurrence of early-onset rapid eye movement (REM) periods (sleep-onset REM periods [SOREMPs]) in PD was assessed. We analyzed data from 46 people with PD (26 males, mean age 63.5 years, mean UPDRS-III-OFF 34.7). The sleep-wake assessment included Epworth sleepiness scale (ESS), Karolinska sleepiness scale (KSS), and objective (polysomnography, multiple sleep latency test [MSLT], and maintenance of wakefulness tests [MWT]) measures. Subjective (ESS ≥ 10) and objective (mean sleep latency, MSL < 5 min in MSLT) EDS were present in 43% and 41% of patients, respectively. The MSL in MSLT and MWT remained unchanged throughout the day and significantly correlated with KSS during the trial but not with KSS shortly before it. In MWT, about one-fourth of patients failed to signal their sleepiness before falling asleep. SOREMPs, usually (83%) arising from NREM1 or wake, were recorded in 24% of the patients. People with SOREMPs had significantly lower MSL in MSLT and MWT and higher AHI compared with those without SOREMPs. Patients with PD exhibit daylong increased EDS but they underestimate its degree and often fail to signal its onset. SOREMPs in PD have a "narcoleptic" character in sleep-stage sequencing and are associated with the presence of sleep-disturbed breathing. These results add to our understanding of sleepiness and sleepiness perception in PD and have important implications for its diagnosis and management.

Ability of the Fitbit Alta HR to quantify and classify sleep in patients with suspected central disorders of hypersomnolence: A comparison against polysomnography.

Measuring sleep duration and early onset rapid eye movement sleep (REMS) is critical in the assessment of suspected central disorders of hypersomnolence (CDH). Current multi-sensor activity trackers that integrate accelerometry and heart rate are purported to accurately quantify sleep time and REMS; however, their utility in suspected CDH has not been established. This investigation aimed to determine the ability of a current, multi-sensor tracker, Fitbit Alta HR (FBA-HR), to quantify and classify sleep in patients with suspected CDH relative to polysomnography (PSG). Forty-nine patients (46 female; mean age,30.3±9.84years) underwent ad libitum PSG with concurrent use of the FBA-HR. FBA-HR sleep variable quantification was assessed using Bland-Altman analysis. FBA-HR all sleep (AS), light sleep (LS; PSG N1+N2), deep sleep (DS; PSG N3) and REMS classification was evaluated using epoch-by-epoch comparisons. FBA-HR-detected sleep-onset rapid eye movement periods (SOREMPs) were compared against PSG SOMREMPs. FBA-HR displayed significant overestimation of total sleep time (11.6min), sleep efficiency (1.98%) and duration of deep sleep (18.2min). FBA-HR sensitivity and specificity were as follows: AS, 0.96, 0.58; LS, 0.73, 0.72;DS, 0.67, 0.92; REMS, 0.74, 0.93. The device failed to detect any nocturnal SOREMPs. Device performance did not differ appreciably among diagnostic subgroups. These results suggest FBA-HR cannot replace EEG-based measurements of sleep and wake in the diagnostic assessment of suspected CDH, and that improvements in device performance are required prior to adoption in clinical or research settings.

Kanashibari Phenomenon as a Sleep Disorder: Recurrent Idiopathic Sleep Paralysis

The phenomenon called kanashibari in Japan is otherwise known as sleep paralysis and, is an established symptom of narcolepsy. Its physiological correlate is an unusual occurrence of rapid eye movement (REM) sleep, i.e., sleep onset REM periods (SOREMPs). Various symptoms of the phenomenon are explained by the mechanisms of REM sleep. SOREMPs can be observed in various situations, which indicate a lower amplitude of circadian rhythms, such as during interupted sleep, acute reversal of sleep and wakefulness cycle, and disrupted sleep of depressive patients and in newborn babies. The lifetime prevalence of the phenomenon in the general population is as high about 40%. The phenomenon can be a mysterious and frightening experience far affected people and called as various names according to the folklore beliefs of local communities, e.g., nightmare in Europe, hexendrücken in Germany, cauchemar in France, and old hag in Newfoundland. Japanese college students are known for their very short sleep length and disturbed sleep wake rhythms. Many students claim to have experienced daytime sleepiness. Some of them meet the criterion concerning sleep latencies and frequency of SOREMPs for multiple sleep latency test (MSLT) as narcolepsy. SOREMPs are frequently seen in healthy college students with certain lifestyles. Practitioners should be cautious to diagnose narcolepsy if the student shows disturbed sleep wake schedules.

Obstructive Sleep Apnea and Sleep Architecture in Adolescents With Severe Obesity: Effects of a 9-Month Lifestyle Modification Program Based on Regular Exercise and a Balanced Diet.

Physical exercise and lifestyle modification are recognized as adjunct therapy for obstructive sleep apnea (OSA) in overweight adults. The objectives of this study were to investigate the effects of long-term physical exercise combined with a balanced diet on sleep architecture, sleep duration, and OSA in adolescents with severe obesity. This interventional study was conducted in a nursing institution. Participants were aged 14.6 ± 1.2 years with obesity (body mass index (BMI) = 40.2 ± 6.5 kg/m2). At admission and at 9 months, participants underwent ambulatory polysomnography and incremental maximal exercise testing to determine cardiorespiratory fitness. Twenty-four subjects completed the study. Analyses were performed on the whole population and on a subgroup of subjects with OSA (OSA-subgroup). OSA, defined as obstructive apnea-hypopnea index (OAHI) ≥ 2 events/h, was diagnosed in 58.3% of the population. OAHI was only associated with fat mass in males (r = .75, P < .05). At 9 months postintervention, weight loss (-11.1 kg, P < .0001) and improved cardiorespiratory fitness (VO2peak: +4.9 mL/min/kg, P < .001) were found in the whole population. Sleep duration was increased (+34 minutes, P < .05) and sleep architecture was changed with an increase of rapid eye movement sleep (+2.5%, P < .05) and a decrease of stage N3 sleep (-3.1%, P < .001). Similar results were found in the OSA subgroup. However, OAHI remained unchanged (P = .18). A combination of supervised aerobic exercise and a balanced diet led to weight loss, improved aerobic capacity, and modified sleep architecture without changes in OSA. A commentary on this article appears in this issue on page 907. Registry: ClinicalTrials.gov, Title: Exercise and Venous Compression on Upper Airway Resistance in Obese Teenagers With OSA (OBESOMAC), URL: https://clinicaltrials.gov/ct2/show/NCT02588469, Identifier: NCT02588469.

Multiple sleep latency test in narcolepsy type 1 and narcolepsy type 2: A 5-year follow-up study.

Excessively sleepy teenagers and young adults without sleep-disordered breathing are diagnosed with either narcolepsy type 1 or narcolepsy type 2, or hypersomnia, based on the presence/absence of cataplexy and the results of a multiple sleep latency test. However, there is controversy surrounding this nomenclature. We will try to find the differences between different diagnoses of hypersomnia from the results of the long-term follow-up evaluation of a sleep study. We diagnosed teenagers who had developed excessive daytime sleepiness based on the criteria of the International Classification of Sleep Disorders, 3rd edition. Each individual received the same clinical neurophysiologic testing every year for 5years after the initial diagnosis of narcolepsy type 1 (n=111) or type 2 (n=46). The follow-up evaluation demonstrated that narcolepsy type 1 (narcolepsy-cataplexy) is a well-defined clinical entity, with very reproducible clinical neurophysiologic findings over time, whereas patients with narcolepsy type 2 presented clear clinical and test variability. By the fifth year of the follow-up evaluation, 17.6% of subjects did not meet the diagnostic criteria of narcolepsy type 2, and 23.9% didn't show any two sleep-onset rapid eye movement periods in multiple sleep latency during the 5-year follow-up. Therefore narcolepsy type 1 (narcolepsy-cataplexy) is a well-defined syndrome, with the presentation clearly related to the known consequences of destruction of hypocretin/orexin neurons. Narcolepsy type 2 covers patients with clinical and test variability over time, thus bringing into question the usage of the term "narcolepsy" to label these patients.

0480 Rapid Eye Movement Period Apnea Contribute to Peripheral Arterial Stiffness in Obstructive Sleep Apnea Syndrome

0480 Rapid Eye Movement Period Apnea Contribute to Peripheral Arterial Stiffness in Obstructive Sleep Apnea Syndrome

Orexin/hypocretin levels in the cerebrospinal fluid and characteristics of patients with myotonic dystrophy type 1 with excessive daytime sleepiness.

PurposeMyotonic dystrophy type 1 (DM1) is often characterized by excessive daytime sleepiness (EDS) and sleep-onset rapid eye movement periods caused by muscleblind-like protein 2. The EDS tends to persist even after treatment of sleep apnea. We measured the cerebrospinal fluid (CSF) orexin levels in DM1 patients with EDS and compared the clinical characteristics with narcolepsy type 1 and idiopathic hypersomnia (IHS) patients.Patients and methodsWe measured the CSF orexin levels in 17 DM1 patients with EDS and evaluated subjective sleepiness using the Epworth Sleepiness Scale (ESS), objective sleepiness using mean sleep latency (MSL), and sleep apnea using apnea-hypopnea index (AHI). We compared the ESS scores and MSL between decreased (≤200 pg/mL) and normal (>200 pg/mL) CSF orexin group in DM1 patients. Furthermore, we compared the CSF orexin levels, ESS scores, MSL, and AHI among patients with DM1, narcolepsy type 1 (n=46), and IHS (n=30).ResultsSeven DM1 patients showed decreased CSF orexin levels. There were significant differences in the ESS scores and MSL between decreased and normal CSF orexin groups in DM1 patients. The ESS scores showed no significant difference among patients with DM1, narcolepsy type 1, and IHS. The MSL in DM1 and IHS patients were significantly higher than narcolepsy type 1 patients (p=0.01, p<0.001). The AHI in DM1 patients was significantly higher than narcolepsy type 1 patients (p=0.042) and was insignificantly different from IHS patients. The CSF orexin levels in DM1 patients were significantly lower than IHS patients and higher than narcolepsy type 1 patients (p<0.001, p<0.001).ConclusionThe CSF orexin levels of DM1 patients moderately decreased compared to those of IHS patients as the control group. However, the EDS of DM1 patients may not be explained by only orexin deficiency.

Different effects of apnea during rapid eye movement period on peripheral arterial stiffness in obstructive sleep apnea

Bakground and aimsObstructive sleep apnea (OSA) contributes to cardiovascular diseases, including arterial stiffness. The association between OSA and peripheral arterial stiffness indices remains controversial. MethodsThis study recruited 275 patients who were referred for sleep apnea study. Arterial stiffness was assessed by peripheral compliance index (CI) and central pulse wave velocity derived from digital volume pulse (PWVDVP) by photoplethysmography. Overnight polysomnography and autonomic nerve system function tests were also conducted. ResultsA total of 275 patients (170 men) were recruited. Most were middle-aged and overweight. Most patients (112/275, 40.7%) had rapid eye movement (REM)-predominant OSA. The CI was significantly correlated with the apnea–hypopnea index (AHI) (R = −0.132, p = 0.029) and AHI-REM (R = −0.170, p = 0.005) and AHI non-REM (R = −0.122, p = 0.043). Among models and variable used to predict CI, only male sex (B = −0.708, p = 0.007) and AHI-REM (B = −0.010, p = 0.033) were independent predictors of CI. An increase in the interquartile range of AHI-REM was associated with a 9.6% decrease in CI. ConclusionsAHI-REM was independently correlated with a peripheral arterial stiffness index, CI. AHI-REM may be a suitable surrogate marker for predicting peripheral arterial stiffness in OSA patients.

Effect of Olanzapine on Clinical and Polysomnography Profiles in Patients with Schizophrenia.

Acute and short-term administration of olanzapine has a favorable effect on sleep in schizophrenia patients. This study aimed to clarify the effect of olanzapine on polysomnographic profiles of schizophrenia patients during the acute phase of illness after controlling for previous drug exposure. Twenty-five drug-naïve or drug-free schizophrenia patients were assessed at baseline and after six weeks of olanzapine treatment on Brief Psychiatric Rating Scale (BPRS), Positive and Negative Syndrome Scale (PANSS), and Udvalg for Kliniske Undersogelser (UKU) side-effect rating scale and a whole-night polysomnography; fifteen patients completed the study. There was a significant reduction in all psychopathological variables with maximum reduction in PANSS total, BPRS total, and PANSS positive scores. A significant increase in total sleep time (TST), sleep efficiency (SE), nonrapid eye movement (NREM) stage 1 duration, stage 3 duration, stage 4 duration, and stage 4 percentage of TST, number of rapid eye movement (REM) periods, REM duration, and REM percentage of TST was observed. REM latency at baseline inversely predicted the reduction in BPRS total and PANSS total and positive scores. In summary, short-term treatment with olanzapine produced significant improvement in clinical and polysomnography profiles of patients with schizophrenia with shorter REM latency predicting a good clinical response.

Brain Lesions and Sleep Onset REM Periods in Routine EEG

Rapid eye movement (REM) sleep usually occurs after 90 minutes of consolidated sleep. Sleep onset REM Period (SOREMP) occurs when REM sleep latency is less than 15 minutes. It is a rare phenomenon, mostly associated with sleep deprivation and narcolepsy. Patients undergoing routine Electroencephalogram (EEG) studies for other reasons than sleep disorders can occasionally have SOREMPs. The objective of this study was to determine the frequency of patients with SOREMPS in routine EEG and to evaluate its possible etiologies. This is a retrospective study of all EEGs performed in the EEG/sleep laboratory from Hospital de Santa Maria-Lisbon, during last 6 years. EEGs with REM sleep were selected. Both ambulatory and EEGs performed in the acute setting were included along with Data for cranial CT-scan or MRI. In 6 years, only 8 patients had SOREMPs, among them, it was possible to obtain cranial MRI or CT-scan in 7 patients (one died). One patient with a psychiatric disorder, showed no lesions on MRI. The other 6 had lesions involving brainstem (n=5) or diencephalon (n=1). The etiologies were inflammatory (2), vascular (3) and infectious (1). All lesions except one were acute. These results suggest that when SOREMPs are detected, lesions involving REM sleep structures should be searched for.

Long-range alpha and beta and short-range gamma EEG synchronization distinguishes phasic and tonic REM periods.

Rapid eye movement (REM) sleep is characterized by the alternation of two markedly different microstates, phasic and tonic REM. These periods differ in awakening and arousal thresholds, sensory processing, and spontaneous cortical oscillations. Previous studies indicate that although in phasic REM, cortical activity is independent of the external environment, attentional functions and sensory processing are partially maintained during tonic periods. Large-scale synchronization of oscillatory activity, especially in the α- and β-frequency ranges, can accurately distinguish different states of vigilance and cognitive processes of enhanced alertness and attention. Therefore, we examined long-range inter- and intrahemispheric as well as short-range electroencephalographic synchronization during phasic and tonic REM periods quantified by the weighted phase lag index. Based on the nocturnal polysomnographic data of 19 healthy adult participants, we showed that long-range inter- and intrahemispheric α and β synchrony was enhanced in tonic REM states in contrast to phasic ones, and resembled α and β synchronization of resting wakefulness. On the other hand, short-range synchronization within the γ-frequency range was higher in phasic compared with tonic periods. Increased short-range synchrony might reflect local and inwardly driven sensorimotor activity during phasic REM periods, whereas enhanced long-range synchrony might index frontoparietal activity that reinstates environmental alertness after phasic REM periods.

Diagnostic value of multiple sleep latency test in children with narcolepsy

Objective To explore the value of multiple sleep latency test (MSLT)in children with narcolepsy, and summarize the clinical features and characteristics of 30 patients. Methods Thirty narcolepsy patients who got treated in Department of Pediatric Neurology, Shengjing Hospital Affiliated to China Medical University were chosen as the experimental group and 38 healthy children were taken as the healthy control group from January 2014 to September 2016.The sleep latency and sleep onset rapid eye movement periods (SOREMPs)with polysomnography were analyzed in order to find the clinical features of narcolepsy and the follow-up for therapeutic effects was evaluated. Results The narcolepsy patients got their disease at an average age of (7.50±2.08)years old, mostly in 6 to 9 years old, the average course of disease was (17.15±1.81)months.Thirty narcolepsy patients got excessive daytime sleepiness, which also came as the first symptom to hospital, and the sleep latency was (2.83±1.36)min, with an average (1.33±1.09)times of SOREMPs, while the healthy control group got (10.40±4.11)min, and there was significant difference between them(P<0.05). Eight patients got limb weakness or cataplexy, 3 patients got sleep paralysis and 3 patients had hypnagogic hallucination.Twenty-three patients(76.7%)got treatment, 14 cases (46.7%)of them got relieved in less than 3 months, 5 cases (16.7%)in 3 to 6 months, and another 4 cases (13.3%)after 6 months, while the other 7 cases (23.3%)did not get systemic therapy, in which symptoms did not get improved. Conclusion Excessive daytime sleepiness acts as a major clinical symptom in children with narcolepsy, while hypnagogic hallucinations and sleep paralysis are relatively infrequent.The peak incidence was in school age, and MSLT can help make an earlier diagnosis. Key words: Narcolepsy; Multiple sleep latency test; Polysomnography; Child

Differences in rapid eye movement (REM) sleep abnormalities between posttraumatic stress disorder (PTSD) and major depressive disorder patients: REM interruption correlated with nightmare complaints in PTSD

ObjectiveThe presence of repeated nightmares in posttraumatic stress disorder (PTSD) has been hypothesized as a dysfunction of rapid eye movement (REM) sleep, but there has been remarkably little agreement about the pathophysiology. This presents a deterrent to more effective treatments. REM sleep abnormalities including elevated REM density also have been replicated in major depressive disorder (MDD). The purpose of this study was to clarify the difference of REM sleep abnormalities between the two disorders for understanding the pathophysiology of sleep disturbances in PTSD. MethodsPolysomnographic measures were compared among 14 PTSD patients (aged 23.7 ± 5.5 years) and 14 MDD patients (aged 27.9 ± 10.1 years) under drug-naive or drug-free conditions. We defined REM interruption by summing the intrusive wake times during the REM period and adding the subsequent wake times to the last epoch of REM period. The significant polysomnographic measures were correlated with PTSD symptoms within the PTSD group. ResultsREM interruption was significantly increased in the PTSD group compared with the MDD group (12.2 vs 2.1 min, p = 0.001). REM density was also significantly increased in the PTSD group compared with the MDD group (30.5 vs 23.1%, p = 0.019). Within the PTSD group, we found significant correlations between the severity of trauma-related nightmare complaints and the percentage of REM interruption (R = 0.62, p = 0.017), but not REM density. ConclusionsREM sleep abnormalities are different between PTSD and MDD. Increased REM interruption may be a biological marker correlated with nightmare complaints in PTSD patients. Treatments including pharmacotherapy that reduces REM interruption might ameliorate nightmares in PTSD.

Optimizing MSLT Specificity in Narcolepsy With Cataplexy.

Multiple sleep onset rapid eye movement (R) periods (SOREMPs) and a mean sleep latency of ≤8 minutes on the multiple sleep latency test (MSLT) are diagnostic criteria of narcolepsy (NC), but also occur in other conditions with increased sleep pressure, including insufficient sleep syndrome (ISS), sleep-disordered breathing (SDB), or Parkinson's disease (PD). These false positives are common, may create diagnostic uncertainty, and highlight the need for complementary MSLT measures with high specificity for NC. Detailed analysis of MSLT findings in 56 NC, 83 PD, 89 SDB, and 23 ISS patients, using receiver operating characteristic curves. A positive MSLT (mean sleep latency ≤ 8.0 minutes and ≥2 SOREMPs) was found in 53 NC (95%), 1 PD (1%), 8 SDB (9%), and 12 ISS patients (52%). MSLT-based differentiation between NC and non-NC patients was best when applying a mean R latency of ≤5 minutes (sensitivity/specificity/positive predictive value [PPV]: 49%/95%/96%) or a mean percentage of sleep stage R ≥ 40% (sensitivity/specificity/PPV: 60%/100%/100%) as cutoffs. When analyzing all 252 naps with SOREMPs in isolation, the combination of both R latency of ≤5 minutes and R percentage of ≥50% yielded a sensitivity/specificity/PPV of 50%/99%/99%. In addition, a sleep stage sequence with R occurring prior to N2 was more common in NC than in non-NC (71% vs. 32%, p < .001), and in combination with R percentage of ≥50% yielded a sensitivity/specificity/PPV of 53%/96%/97%. A better characterization of R sleep by latency, duration, and sleep stage sequence facilitates detection of false positives and, hence, contributes to a higher MSLT specificity in NC.

Sleepless Night and Day, the Plight of Progressive Supranuclear Palsy.

To elucidate the unique sleep and waking characteristics in progressive supranuclear palsy (PSP), a neurodegenerative disease associated with motor deficits and dementia that largely affects the brainstem and thalamic regions. A total of 20 PSP and 16 healthy older adult controls participated in this study. The participants underwent an overnight polysomnography and multiple sleep latency test (MSLT) the following day. Prior to the MSLT last trial, they were asked to complete the Stanford Sleepiness Scale. Data were assessed for measures of latency to sleep onset, sleep duration, waking, and sleep staging during the night. Mean sleep latency, a measure of daytime sleepiness, sleep onset rapid eye movement (REM) periods, and microsleeps were studied with the MSLT. Spectral analysis of wake electroencephalogram (EEG) was performed for 30-second periods at the start of each MSLT trial. PSP took significantly longer time to fall asleep (p < .001), slept less during the night (p ≤ .001), and had more wake after sleep onset than controls (p ≤ .001). PSP had less N2 sleep (p < .05) and N3 sleep (p < .05), and REM sleep (p < .001) than controls. During the MSLT, PSP took significantly longer to fall asleep (p < .001), did not have microsleeps when they remained awake throughout the assessment periods, but were subjectively sleepier than controls (p < .05). Gamma power was increased during wake EEG in PSP (p < .01). Sleep/waking regulation and REM sleep regulation are disrupted in PSP, leading to profound sleep deprivation without recuperation. Our findings suggest a diminished homeostatic sleep drive in PSP. This hyperaroused state is unique and is a severely disabling feature of PSP.

Psychomotor Vigilance Test and Its Association With Daytime Sleepiness and Inflammation in Sleep Apnea: Clinical Implications.

Excessive daytime sleepiness (EDS) is a key symptom of obstructive sleep apnea (OSA). The Psychomotor Vigilance Task (PVT) has been suggested as an objective easy-to-use, inexpensive alternative to the Multiple Sleep Latency Test (MSLT) to measure EDS. In patients with OSA, physiological sleepiness, but not subjective EDS (Epworth Sleepiness Scale [ESS]), has been associated with increased levels of the sleep- inducing proinflammatory cytokine interleukin-6 (IL-6). The goal of this study was to assess the association of PVT with objectively measured sleepiness (MSLT) and subjectively measured sleepiness (ESS) and IL-6 levels in patients with OSA. We studied 58 untreated patients with OSA who underwent an 8-hour in-laboratory polysomnography for 4 consecutive nights. MSLT, PVT, and 24-hour serial profiles of IL-6 were assessed on the fourth day. PVT variables included number of lapses, mean reciprocal of the fastest 10% and slowest 10% reaction times, and median of 1/reaction time. ESS was assessed on day 1 of the study. Higher ESS scores were significantly associated with greater number of lapses (β = .34, P = .02) and lower values of 1/RT (β = -.36, P = .01) and slowest 10% RTs (β = -.30, P = .04). No significant association was observed between PVT and MSLT, nor PVT and IL-6 levels. Our findings suggest that PVT is associated with subjectively assessed daytime sleepiness, but not with physiological sleepiness nor IL-6 levels in patients with OSA. It appears that ESS and PVT may be useful in predicting risks associated with impaired performance, such as traffic accidents, in patients with OSA.

S170 REM – Dreaming – Emotions: The neurophysiology of nightmare disorder

Objectives Nightmares are intense and highly unpleasant mental experiences that occur usually – but not exclusively – during late-night Rapid Eye Movement (REM) sleep and often provoke abrupt awakenings.The underlying mechanism of nightmare disorder was only scarcely investigated and remains poorly understood. The most influential model of nightmare disorder that provided a common framework fortrauma-related and non-traumatic (idiopathic) nightmares was introduced by Levin and Nielsen (2007). One of the main assumptions of the model is that nightmares reflect unsuccessful fear-extinction processes during (REM) sleep due to a dysfunctional brain network comprising fronto-limbic structures. Consequently, amygdalar over-activation and inefficient (prefrontal) inhibition lead to the emotional intensification of dreaming and hyperarousal during sleep. Nevertheless, sleep quality and emotional regulation in nightmare sufferers was mainly examined by questionnaire-based studies. Methods We have performed a series of quantitative EEG analyses based on the polysomnographic data of young (non-ptsd) nightmare sufferers and matched controls. Moreover, in a subsequent study we investigated emotional habituation to arousing images after a night of polysomnographically monitored sleep in a group of nightmare sufferers and matched controls. Emotional reactivity was quantified by subjective evaluations and psychophysiological measures (HRV, SCR). Results In line with questionnaire-based findings, we found that nightmare sufferers are characterized by fragmented sleep, reduced Slow Wave Sleep (SWS), enhanced microarousals during NREM sleep and heightened wake-like oscillations during REM sleep. Furthermore, arousal-related cortical activity coupled with attenuated parasympathetic regulation were evidenced in nightmare sufferers specifically during NREM to REM transitions. Discussion Given that the neural network underlying emotional memory processing is highly active during REM periods, and REM sleep seems to be intimately related to fear memory processing, our findings might indirectly support Levin and Nielsen’s assumption of disrupted REM-dependent fear-extinction in nightmare disorder. Nevertheless, the association between impaired emotional regulation and altered sleep physiology remains to be investigated. Conclusions In our experiments we aimed to directly test Levin and Nielsen’s fear-extintion model of nightmare disorder and to relate impaired emotional regulation to specific sleep EEG features. We conclude that examining nightmare disorder by such integrative approach would shed more light on the enigma of REM sleep and emotional memory processing. Significance Our research could shed more light on the mechanism of nightmare formation, propagate the professional knowledge of nightmare disorder, and facilitate the development of effective, evidence-based treatment procedures.

Eye movement activity in normal human fetuses between 24 and 39 weeks of gestation

Rapid eye movement (REM) sleep occurs throughout a relatively large proportion of early development, and normal REM activity appears to be required for healthy brain development. The eye movements (EMs) observed during REM sleep are the most distinctive characteristics of this state. EMs are used as an index of neurological function postnatally, but no specific indices of EM activity exist for fetuses. We aimed to identify and characterize EM activity, particularly EM bursts suggestive of REM periods, in fetuses with a gestational age between 24 and 39 weeks. This cross-sectional study included 84 normal singleton pregnancies. Fetal EMs were monitored using real-time ultrasonography for 60 min and recorded as videos. The videos were manually converted into a time series of EM events, which were then analyzed by piecewise linear regression for various EM characteristics, including EM density, EM burst density, density of EMs in EM bursts, and continuous EM burst time. Two critical points for EM density, EM burst density, and density of EMs in EM bursts were evident at gestation weeks 28–29 and 36–37. Overall EM activity in human fetuses increased until 28–29 weeks of gestation, then again from 36–37 to 38–39 weeks of gestation. These findings may be useful for creating indices of fetal neurological function for prognostic purposes.

Heart rate variability in patients with major depressive disorder and healthy controls during non-REM sleep and REM sleep.

The objectives of this study are to investigate heart rate variability (HRV) in major depressive disorder patients (MDD) and healthy controls during different sleep stages, and to examine the association of HRV during sleep and depression severity. Polysomnography was recorded from 15 depressive patients with a higher beck depression inventory index (BDI > 25, H-BDI-D), 15 depressive patients with a lower BDI index (BDI ≤ 25, L-BDI-D) and 15 healthy controls. HRV was calculated during the first three rapid eye movements (REM) periods and non-REM stages (i.e. sleep stage 2 and 3) with time domain, power spectral and fractal analysis. As a result, H-BDI-D patients showed the highest short-term fractal alpha-1 exponent during first REM period and healthy controls had the lowest values. Our results suggest an association between the depression severity and the autonomic nerve function, especially during the first REM sleep. The pathophysiological analysis for this property should be conducted in future prospective studies.

Why Do Healthy Men Experience Morning Erections?

People begin the sleep cycle with a period of non-rapid eye movement (NREM) sleep, followed by a very short period of rapid eye movement (REM) sleep. During a normal night of sleep, humans usually experience about four or five periods of REM sleep. Penile erections have generally been considered to be an epiphenomenon of REM sleep-related physiological changes for healthy males. Thus, men are very likely to awaken in the morning with a REM sleep-related erection, which is also known as nocturnal penile tumescence (NPT). Men who are physically under great strain or serious psychological stress may find it difficult to maintain a psychogenic erection. The best time for them to have sex would be during sleep time, such as when they are experiencing REM sleep-related erections. It is reasonable to assume that the NPT phenomena might have evolved as a tool for having sex, in the context of both procreation and recreation.