Familiarization with ambulatory sleep and blood pressure monitoring is necessary for representative data collection

Ambulatory sleep and blood pressure monitoring are gaining popularity as these can be completed in an individual's home. Little is known regarding the reliability of data and the time it takes to acclimate to the equipment. This study aimed to determine how many nights of wearing the monitoring equipment were required to restore sleep architecture and blood pressure data to baseline. It was hypothesized familiarization would be demonstrated by night 3. Ten male and 10 female subjects completed three nights of sleep and blood pressure recordings. At visit 1, the subjects were familiarized with the equipment and instructed to wear the Sleep Profiler{trade mark, serif} and SunTech Medical Oscar2 ambulatory blood pressure cuff simultaneously for three consecutive nights, then subjects returned the equipment. The percent of time spent in rapid eye-movement (REM) sleep was statistically different on night 3 when compared to night 1. Wake-after-sleep onset and sleep latency were not statistically different between nights 1, 2, and 3. Systolic, diastolic, and pulse pressure were all significantly lower on night 3 compared to night 1. Cortical and autonomic arousals were statistically different on night 3. Ambulatory sleep and blood pressure monitoring need at least 3 nights for familiarization. The percent of time spent in REM sleep was statistically different on night 3 when compared to night 1. Systolic blood pressure, diastolic blood pressure, and pulse pressure were all significantly lower on night 3 compared to night 1. Cortical and autonomic arousals were statistically different on nights 3 and 2, respectively compared to night 1. Based on these findings, ambulatory sleep and blood pressure monitoring takes three nights before the data are reliable and the person is familiarized with the mode of measurement. Therefore, it is recommended to use at least three nights of data collection when using the Sleep Profiler and Oscar2 ambulatory blood pressure cuff in order for results to be valid and reliable.

Regional variation in cholinergic terminal activity determines the non-uniform occurrence of cortical slow waves during REM sleep in mice

Sleep consists of two basic stages: non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. NREM sleep is characterized by slow high-amplitude cortical electroencephalogram (EEG) signals, while REM sleep is characterized by desynchronized cortical rhythms. Despite this, recent electrophysiological studies have suggested the presence of slow waves (SWs) in local cortical areas during REM sleep. Electrophysiological techniques, however, have been unable to resolve the regional structure of these activities because of relatively sparse sampling. Here, we map functional gradients in cortical activity during REM sleep using mesoscale imaging in mice and show local SW patterns occurring mainly in somatomotor and auditory cortical regions with minimum presence within the default mode network. The role of the cholinergic system in local desynchronization during REM sleep is also explored by calcium imaging of cholinergic activity within the cortex and analyzing structural data. We demonstrate weaker cholinergic projections and terminal activity in regions exhibiting frequent SWs during REM sleep.

Non-rapid eye movement sleep determines resilience to social stress

Resilience, the ability to overcome stressful conditions, is found in most mammals and varies significantly among individuals. A lack of resilience can lead to the development of neuropsychiatric and sleep disorders, often within the same individual. Despite extensive research into the brain mechanisms causing maladaptive behavioral-responses to stress, it is not clear why some individuals exhibit resilience. To examine if sleep has a determinative role in maladaptive behavioral-response to social stress, we investigated individual variations in resilience using a social-defeat model for male mice. Our results reveal a direct, causal relationship between sleep amount and resilience-demonstrating that sleep increases after social-defeat stress only occur in resilient mice. Further, we found that within the prefrontal cortex, a regulator of maladaptive responses to stress, pre-existing differences in sleep regulation predict resilience. Overall, these results demonstrate that increased NREM sleep, mediated cortically, is an active response to social-defeat stress that plays a determinative role in promoting resilience. They also show that differences in resilience are strongly correlated with inter-individual variability in sleep regulation.

Saikosaponin a promotes sleep by decreasing neuronal activities in the lateral hypothalamus

Insomnia is one of the most prevalent sleep disorders, which imparts tremendous societal and economic impact. However, the present pharmacotherapy is greatly limited by adverse effects, so it is necessary to explore new drugs for the treatment of insomnia. Radix Bupleuri (RB) has been widely used in traditional Chinese medicine for >2000 years; it has many pharmacological effects, including sedation and anticonvulsant properties. The present study investigated the effects of saikosaponin a (SSa), an active component of RB, on sleep and locomotion. Male C57BL/6j mice received intraperitoneal injections of SSa at three different dosages (0.625, 1.25, and 2.5 mg/kg). Sleep parameters were analysed by electroencephalography and electromyography. The open-field test was used to measure locomotor activities. Our present results showed that SSa treatment significantly increased the duration of non-rapid eye movement sleep and shortened sleep latency in a dose-dependent manner. A high dose of SSa (2.5 mg/kg) also decreased locomotor activities. Moreover, by measuring c-Fos expression and the calcium signal in the lateral hypothalamus (LH), we found that SSa treatment decreased neuronal activity in the LH. In conclusion, SSa might be the sleep-promoting component in RB and its mechanism may be related to the modulation of neuronal activity in the LH.

Fermented Gamma Aminobutyric Acid Improves Sleep Behaviors in Fruit Flies and Rodent Models

The aim of this study was to investigate the effect of Lactobacillus brevis-fermented γ-aminobutyric acid (LB-GABA) on sleep behaviors in invertebrate and vertebrate models. In Drosophila melanogaster, LB-GABA-treated group showed an 8-9%-longer sleep duration than normal group did. LB-GABA-treated group also showed a 46.7% lower level of nighttime activity with a longer (11%) sleep duration under caffeine-induced arousal conditions. The LB-GABA-mediated inhibition of activity was confirmed as a reduction of total movement of flies using a video tracking system. In the pentobarbital-induced sleep test in mice, LB-GABA (100 mg/kg) shortened the time of onset of sleep by 32.2% and extended sleeping time by 59%. In addition, mRNA and protein level of GABAergic/Serotonergic neurotransmitters were upregulated following treatment with LB-GABA (2.0%). In particular, intestine- and brain-derived GABAA protein levels were increased by sevenfold and fivefold, respectively. The electroencephalography (EEG) analysis in rats showed that LB-GABA significantly increased non-rapid eye movement (NREM) (53%) with the increase in theta (θ, 59%) and delta (δ, 63%) waves, leading to longer sleep time (35%), under caffeine-induced insomnia conditions. LB-GABA showed a dose-dependent agonist activity on human GABAA receptor with a half-maximal effective concentration (EC50) of 3.44 µg/mL in human embryonic kidney 293 (HEK293) cells.

Nicotine increases sleep spindle activity

Studies have shown that both nicotine and sleep spindles are associated with enhanced memorisation. Further, a few recent studies have shown how cholinergic input through nicotinic and muscarinic receptors can trigger or modulate sleep processes in general, and sleep spindles in particular. To better understand the interaction between nicotine and sleep spindles, we compared in a single blind randomised study the characteristics of sleep spindles in 10 healthy participants recorded for 2 nights, one with a nicotine patch and one with a sham patch. We investigated differences in sleep spindle duration, amplitude, intra-spindle oscillation frequency and density (i.e. spindles per min). We found that under nicotine, spindles are more numerous (average increase: 0.057 spindles per min; 95% confidence interval: [0.025-0.089]; p = .0004), have higher amplitude (average amplification: 0.260 μV; confidence interval: [0.119-0.402]; p = .0032) and last longer (average lengthening: 0.025 s; confidence interval: [0.017-0.032]; p = 2.7e-11). These results suggest that nicotine can increase spindle activity by acting on nicotinic acetylcholine receptors, and offer an attractive hypothesis for common mechanisms that may support memorisation improvements previously reported to be associated with nicotine and sleep spindles.

The effect of dream report collection and dream incorporation on memory consolidation during sleep

Collecting dream reports typically requires waking subjects up from their sleep—a method that has been used to study the relationship between dreams and memory consolidation. However, it is unclear whether these awakenings influence sleep‐associated memory consolidation processes. Furthermore, it is unclear how the incorporation of the learning task into dreams is related to memory consolidation. In this study we compared memory performance in a word–picture association learning task after a night with and without awakenings in 22 young and healthy participants. We then examined if the stimuli from the learning task are successfully incorporated into dreams, and if this incorporation is related to the task performance the next morning. We show that while the awakenings impaired both subjective and objective sleep quality, they did not affect sleep‐associated memory consolidation. When dreams were collected during the night by awakenings, memories of the learning task were successfully incorporated into dreams. When dreams were collected in the morning, no incorporations were detected. Task incorporation into non‐rapid eye movement sleep dreams, but not rapid eye movement sleep dreams positively predicted memory performance the next morning. We conclude that the method of awakenings to collect dream reports is suitable and necessary for dream and memory studies. Furthermore, our study suggests that dreams in non‐rapid eye movement rather than rapid eye movement sleep might be related to processes of memory consolidation during sleep.

Romaine Lettuce/Skullcap Mixture Improves Sleep Behavior in Vertebrate Models

The aim of this study is to investigate the effects of romaine lettuce leaves extract (RE), skullcap root extract (SE) and their mixture on sleep behaviors in vertebrate models. HPLC analysis showed that RE contains lactucopicrin (0.02±0.01 mg/g extract), chlorogenic acid (4.05±0.03 mg/g extract), caffeic acid (2.38±0.03 mg/g extract), and chicoric acid (7.02±0.32 mg/g extract) as main phenolic compounds, while SE includes baicalin (99.4±0.5 mg/g extract), baicalein (8.28±0.21 mg/g extract), and wogonin (3.09±0.32 mg/g extract). The mixture of RE (100 mg/g extract) and SE (40 mg/g extract) increased total sleep time by 50.9% compared with the control in pentobarbital-induced sleep model. In electroencephalography (EEG) analysis, RE/SE mixture significantly increased Non-Rapid Eye Movement (NREM), in which delta wave was enhanced by around 40% compared with normal control, leading to the increase of sleep time. In caffeine-induced wake model, RE/SE mixture greatly decreased (53%) caffeine-induced wake time, showing a similar level to normal control. In addition, caffeine-induced decreased of NREM and delta wave effectively increased with RE/SE mixture; NREM and delta wave increased by 85% and 108%, respectively. Furthermore, RE/SE mixture was shown to bind to a gamma-aminobutyric acid type A (GABAA)-benzodiazepine (BZD) receptor stronger than RE or SE single extract. Taken together, RE/SE mixture effectively improved sleep behavior with the increase of NREM via GABAA-BZD receptor binding. RE/SE mixture can be used as an herbal agent for sleep disorders.

Treatment Approach to Sleep Terror: Two Case Reports

Parasomnias are a group of disorders characterized by abnormal behaviors, physical activities, and autonomic arousal symptoms while transition to sleep or continuation of sleep. Sleep terror (ST) is classified under parasomnias characterized by sudden fear attacks beginning with crying attacks or high-frequency screams and continuing with increased autonomic symptoms. ST occurs in the first few hours of sleep during the delta phase. Further, the lifetime prevalence of ST in adults is less than 1%. It is important to obtain; anamnesis from patients' bed partner for a clinical evaluation of ST. Methods, such as evaluating sleep diaries and video recordings, can help ST diagnosis. It is also important to evaluate patients' medical history, history of substance or alcohol abuse, psychological traumatic experiences, primary or secondary incomes, and detailed neurological aspects. Physician can select some serotonin reuptake inhibitors (SSRIs) or tricyclic antidepressants (TCADs) as medical treatment if patients have a high frequency of attacks. Because of addiction and relapse of ST episodes, benzodiazepines are not preferred as the first-line treatment. In this study, we will discuss ST, which is rare in adulthood, and use of long-acting benzodiazepine based on two cases.

Sleep-wake and diurnal modulation of nitric oxide in the perifornical-lateral hypothalamic area: real-time detection in freely behaving rats

Nitric oxide (NO) has been implicated in the regulation of sleep. The perifornical-lateral hypothalamic area (PF-LHA) is a key wake-promoting region and contains neurons that are active during behavioral or cortical activation. Recently, we found higher levels of NO metabolites (NOx), an indirect measure of NO levels, in the PF-LHA during prolonged waking (SD). However, NO is highly reactive and diffuses rapidly and the NOx assay is not sensitive enough to detect rapid-changes in NO levels across spontaneous sleep-waking states. We used a novel Nafion®-modified Platinum (NF-PT) electrode for real-time detection of NO levels in the PF-LHA across sleep-wake cycles, dark-light phases, and during SD. Sprague-Dawley male rats were surgically prepared for chronic sleep-wake recording and implantation of NF-PT electrode into the PF-LHA. Electroencephalogram (EEG), electromyogram (EMG), and electrochemical current generated by NF-PT electrode were continuously acquired for 5-7days including one day with 3h of SD. In the PF-LHA, NO levels exhibited a waking>rapid eye movement (REM)>non-rapid eye movement (nonREM) sleep pattern (0.56±0.03μM>0.47±0.02μM>0.42±0.02μM; p<0.01). NO levels were also higher during the dark- as compared to the light-phase (0.53±0.03μM vs. 0.44±0.02μM; p<0.01). NO levels increased during 3h of SD as compared to undisturbed control (0.58±0.04μM vs. 0.47±0.01μM; p<0.05). The findings indicate that in the PF-LHA, NO is produced during behavioral or cortical activation. Since elevated levels of NO inhibits most of the PF-LHA neurons that are active during cortical activation, these findings support a hypothesis that NO produced in conjunction with the activation of PF-LHA neurons during waking/SD, inhibits the same neuronal population to promote sleep.

Sleep allostasis in chronic sleep restriction: the role of the norepinephrine system

Sleep responses to chronic sleep restriction may be very different from those observed after acute total sleep deprivation. Specifically, when sleep restriction is repeated for several consecutive days, animals express attenuated compensatory increases in sleep time and intensity during daily sleep opportunities. The neurobiological mechanisms underlying these adaptive, or more specifically, allostatic, changes in sleep homeostasis are unknown. Several lines of evidence indicate that norepinephrine may play a key role in modulating arousal states and NREM EEG delta power, which is widely recognized as a marker for sleep intensity. Therefore, we investigated time course changes in brain adrenergic receptor mRNA levels in response to chronic sleep restriction using a rat model. Here, we observed that significantly altered mRNA levels of the α1- adrenergic receptor in the basal forebrain as well as α2- and β1-adrenergic receptor in the anterior cingulate cortex only on the first sleep restriction day. On the other hand, the frontal cortex α1-, α2-, and β1-adrenergic receptor mRNA levels were reduced throughout the period of sleep restriction. Combined with our earlier findings on EEG that sleep time and intensity significantly increased only on the first sleep restriction days, these results suggest that alterations in the brain norepinephrine system in the basal forebrain and cingulate cortex may mediate allostatic changes in sleep time and intensity observed during chronic sleep restriction.

Technical advances in the characterization of the complexity of sleep and sleep disorders

The current clinical standard for quantifying sleep physiology is the laboratory polysomnogram, from which basic sleep-wake stages are determined. However, the complexity of sleep physiology has inspired alternative metrics that are providing additional insights into the rich dynamics of sleep. Electro-encephalography, magneto-encephalography, and functional magnetic resonance imaging represent advanced imaging modalities for understanding brain dynamics. These methods are complemented by autonomic measurements that provide additional important insights. We review here the spectrum of approaches that have been leveraged towards improved understanding of the complexity of sleep.

Intrinsic connectivity network mapping in young children during natural sleep

Structural and functional neuroimaging have substantively informed the pathophysiology of numerous adult neurological and psychiatric disorders. While structural neuroimaging is readily acquired in sedated young children, pediatric application of functional neuroimaging has been limited by the behavioral demands of in-scanner task performance. Here, we investigated whether functional magnetic resonance imaging (fMRI) acquired during natural sleep and without experimental stimulation offers a viable strategy for studying young children. We targeted the lengthy epoch of non-rapid eye movement, stage 3 (NREM3) sleep typically observed at sleep onset in sleep-deprived children. Seven healthy, preschool-aged children (24-58 months) were studied, acquiring fMRI measurements of cerebral blood flow (CBF) and of intrinsic connectivity networks (ICNs), with concurrent sleep-stage monitoring. ICN data (T2* fMRI) were reliably obtained during NREM3 sleep; CBF data (arterial spin labeled fMRI) were not reliably obtained, as scanner noises disrupted sleep. Applying independent component analysis (ICA) to T2* data, distinct ICNs were observed which corresponded closely with those reported in the adult literature. Notably, a network associated with orthography in adults was not observed, suggesting that ICNs exhibit a developmental trajectory. We conclude that resting-state fMRI obtained in sleep is a promising paradigm for neurophysiological investigations of young children.

Sleep active cortical neurons expressing neuronal nitric oxide synthase are active after both acute sleep deprivation and chronic sleep restriction

Non-rapid eye movement (NREM) sleep electroencephalographic (EEG) delta power (~0.5-4 Hz), also known as slow wave activity (SWA), is typically enhanced after acute sleep deprivation (SD) but not after chronic sleep restriction (CSR). Recently, sleep-active cortical neurons expressing neuronal nitric oxide synthase (nNOS) were identified and associated with enhanced SWA after short acute bouts of SD (i.e., 6h). However, the relationship between cortical nNOS neuronal activity and SWA during CSR is unknown. We compared the activity of cortical neurons expressing nNOS (via c-Fos and nNOS immuno-reactivity, respectively) and sleep in rats in three conditions: (1) after 18-h of acute SD; (2) after five consecutive days of sleep restriction (SR) (18-h SD per day with 6h ad libitum sleep opportunity per day); (3) and time-of-day matched ad libitum sleep controls. Cortical nNOS neuronal activity was enhanced during sleep after both 18-h SD and 5 days of SR treatments compared to control treatments. SWA and NREM sleep delta energy (the product of NREM sleep duration and SWA) were positively correlated with enhanced cortical nNOS neuronal activity after 18-h SD but not 5days of SR. That neurons expressing nNOS were active after longer amounts of acute SD (18h vs. 6h reported in the literature) and were correlated with SWA further suggest that these cells might regulate SWA. However, since these neurons were active after CSR when SWA was not enhanced, these findings suggest that mechanisms downstream of their activation are altered during CSR.