Sleep neurobiology from a clinical perspective

Neural oscillations demonstrate that general anesthesia and sedative states are neurophysiologically distinct from sleep

General anesthesia is a man-made neurophysiological state comprised of unconsciousness, amnesia, analgesia, and immobility along with maintenance of physiological stability. Growing evidence suggests that anesthetic-induced neural oscillations are a primary mechanism of anesthetic action. Each anesthetic drug class produces distinct oscillatory dynamics that can be related to the circuit mechanisms of drug action. Sleep is a naturally occurring state of decreased arousal that is essential for normal health. Physiological measurements (electrooculogram, electromyogram) and neural oscillatory (electroencephalogram) dynamics are used to empirically characterize sleep into rapid eye movement sleep and the three stages of non-rapid eye movement sleep. In this review, we discuss the differences between anesthesia- and sleep-induced altered states from the perspective of neural oscillations.

Orexin System: The Key for a Healthy Life

The orexin-A/hypocretin-1 and orexin-B/hypocretin-2 are neuropeptides synthesized by a cluster of neurons in the lateral hypothalamus and perifornical area. Orexin neurons receive a variety of signals related to environmental, physiological and emotional stimuli, and project broadly to the entire CNS. Orexin neurons are “multi-tasking” neurons regulating a set of vital body functions, including sleep/wake states, feeding behavior, energy homeostasis, reward systems, cognition and mood. Furthermore, a dysfunction of orexinergic system may underlie different pathological conditions. A selective loss orexin neurons was found in narcolepsia, supporting the crucial role of orexins in maintaining wakefulness. In animal models, orexin deficiency lead to obesity even if the consume of calories is lower than wildtype counterpart. Reduced physical activity appears the main cause of weight gain in these models resulting in energy imbalance. Orexin signaling promotes obesity resistance via enhanced spontaneous physical activity and energy expenditure regulation and the deficiency/dysfunction in orexins system lead to obesity in animal models despite of lower calories intake than wildtype associated with reduced physical activity. Interestingly, orexinergic neurons show connections to regions involved in cognition and mood regulation, including hippocampus. Orexins enhance hippocampal neurogenesis and improve spatial learning and memory abilities, and mood. Conversely, orexin deficiency results in learning and memory deficits, and depression.

Lack of Responsiveness during the Onset and Offset of Sevoflurane Anesthesia Is Associated with Decreased Awake-Alpha Oscillation Power

Anesthetic drugs are typically administered to induce altered states of arousal that range from sedation to general anesthesia (GA). Systems neuroscience studies are currently being used to investigate the neural circuit mechanisms of anesthesia-induced altered arousal states. These studies suggest that by disrupting the oscillatory dynamics that are associated with arousal states, anesthesia-induced oscillations are a putative mechanism through which anesthetic drugs produce altered states of arousal. However, an empirical clinical observation is that even at relatively stable anesthetic doses, patients are sometimes intermittently responsive to verbal commands during states of light sedation. During these periods, prominent anesthesia-induced neural oscillations such as slow-delta (0.1–4 Hz) oscillations are notably absent. Neural correlates of intermittent responsiveness during light sedation have been insufficiently investigated. A principled understanding of the neural correlates of intermittent responsiveness may fundamentally advance our understanding of neural dynamics that are essential for maintaining arousal states, and how they are disrupted by anesthetics. Therefore, we performed a high-density (128 channels) electroencephalogram (EEG) study (n = 8) of sevoflurane-induced altered arousal in healthy volunteers. We administered temporally precise behavioral stimuli every 5 s to assess responsiveness. Here, we show that decreased eyes-closed, awake-alpha (8–12 Hz) oscillation power is associated with lack of responsiveness during sevoflurane effect-onset and -offset. We also show that anteriorization—the transition from occipitally dominant awake-alpha oscillations to frontally dominant anesthesia induced-alpha oscillations—is not a binary phenomenon. Rather, we suggest that periods, which were defined by lack of responsiveness, represent an intermediate brain state. We conclude that awake-alpha oscillation, previously thought to be an idling rhythm, is associated with responsiveness to behavioral stimuli.

Infant sleep and its relation with cognition and growth: a narrative review

OBJECTIVE

Infant sleep development is a highly dynamic process occurring in parallel to and in interaction with cognitive and physical growth. This narrative review aims to summarize and discuss recent literature and provide an overview of the relation between infant sleep and cognitive development as well as physical growth.

METHODS

We conducted online literature search using MEDLINE, Embase, and Cochrane Library databases. We considered original research on humans published in the English language from January 2005 to December 2015. Search terms included "sleep" AND "infant" AND "cognition" OR "memory" OR "executive functioning", OR "growth" OR "obesity" OR "growth hormone" OR "stunting", and combinations thereof.

RESULTS

Ten studies on infant sleep and cognition were included in this review. Overall, findings indicated a positive association between sleep, memory, language, executive function, and overall cognitive development in typically developing infants and young children. An additional 20 studies support the positive role of infant sleep in physical growth, with the current literature focusing largely on weight gain and obesity rather than healthy growth. Existing evidence in both the domains is mainly based on cross-sectional designs, on association studies, and on parental reports. In contrast, there were limited studies on longitudinal sleep trajectories and intervention effects, or studies have not used more objective sleep measures such as actigraphy and polysomnography.

CONCLUSION

The reviewed studies support a critical and positive role of infant sleep in cognition and physical growth. Future studies should consider key environmental and parental confounders, include a combination of more objective (actigraphy) and subjective measures (sleep diaries and questionnaires), and move towards longitudinal trajectory designs of infant sleep and development.

Dietary Patterns and Insomnia Symptoms in Chinese Adults: The China Kadoorie Biobank

Limited attention has been paid to the effect of dietary patterns on sleep problems. In the present study, we analyzed the cross-sectional data of 481,242 adults aged 30-79 years from the China Kadoorie Biobank. A laptop-based questionnaire was administered to collect information on food intakes and insomnia symptoms. Logistic regression was used to estimate the odds ratios of each insomnia symptom according to quartiles of each dietary pattern, with adjustment for potential confounders. Two major dietary patterns were derived by factor analysis. The traditional northern dietary pattern was characterized by high intakes of wheat and other staple food, whereas the modern dietary pattern was characterized by high intakes of meat, poultry, fish, eggs, fresh fruit, and dairy products. Both dietary patterns were associated with a decreased prevalence of insomnia symptoms (p for trend < 0.001); after adjustment for potential confounders, individuals who had the highest quartile score of traditional northern dietary pattern were 12%-19% less likely to have insomnia symptoms compared to those in the lowest quartile (odds ratio: 0.81-0.88), and the corresponding values for the modern dietary pattern were 0.89-1.01. Furthermore, interactions of these two dietary patterns on insomnia symptoms were observed. Further prospective studies are needed to elucidate the relationship between diet and insomnia.

Selective agonism of mGlu8 receptors by (S)-3,4-dicarboxyphenylglycine does not affect sleep stages in the rat

BACKGROUND

Metabotropic glutamate receptors (mGlu) play a role in a number of physiological processes and behaviors, as well as in certain pathological conditions and diseases. New drugs targetting mGlu receptors are being developed with treatment purposes. Recent data indicates that glutamate is involved in sleep, and pharmacological manipulation of distinct subtypes of mGlu receptors affect sleep. Here the consequences of selective pharmacological agonism of mGlu8 receptor upon sleep and wakefulness are explored for the first time.

METHODS

32 male Wistar rats were stereotaxically prepared for polysomnography. (S)-3,4-dicarboxyphenylglycine (S)-3,4-DCPG (5, 10, and 20mg/kg, ip), a selective and potent mGlu8 receptor agonist, or physiological saline was administered one hour after the light period began.

RESULTS

Compared to control vehicle, (S)-3,4-DCPG, did not affect, at any of the doses given, the sleep and wakefulness parameters examined in the general analysis of the three hours of recording. Drug effects across time were studied analyzing three one-hour time blocks, control and experimental groups did not show any significant difference in the sleep and wakefulness parameters analyzed. Latency to sleep stages did not significantly vary between vehicle and treatment groups.

CONCLUSIONS

Results indicate that pharmacological activation of mGlu8 receptor by (S)-3,4-DCPG (5, 10, 20mg/kg, ip) does not affect sleep and wakefulness in the rat, suggesting that pharmacological agonism of these receptors may not influence sleep. Further research is needed to verify whether new drugs acting on these receptors lack of effect upon sleep and wakefulness.

Evolution of severe sleep-wake cycle disturbances following traumatic brain injury: a case study in both acute and subacute phases post-injury

Background

Sleep-wake disturbances are frequently reported following traumatic brain injury (TBI), but they remain poorly documented in the acute stage of injury. Little is known about their origin and evolution.

Case presentation

This study presents the case of a patient in the acute phase of a severe TBI. The patient was injured at work when falling 12 m into a mine and was hospitalized in the regular wards of a level I trauma centre. From days 31 to 45 post-injury, once he had reached a level of medical stability and continuous analgosedation had been ceased, his sleep-wake cycle was monitored using actigraphy. Results showed significant sleep-wake disturbances and severe sleep deprivation. Indeed, the patient had an average nighttime sleep efficiency of 32.7 ± 15.4 %, and only an average of 4.8 ± 1.3 h of sleep per 24-h period. After hospital discharge to the rehabilitation centre, where he remained for 5 days, the patient was readmitted to the same neurological unit for paranoid delusions. During his second hospital stay, actigraphy recordings resumed from days 69 to 75 post-injury. A major improvement in his sleep-wake cycle was observed during this second stay, with an average nighttime sleep efficiency of 96.3 ± 0.9 % and an average of 14.1 ± 0.9 h of sleep per 24-h period.

Conclusion

This study is the first to extensively document sleep-wake disturbances in both the acute and subacute phases of severe TBI. Results show that prolonged sleep deprivation can be observed after TBI, and suggest that the hospital environment only partially contributes to sleep-wake disturbances. Continuous actigraphic monitoring may prove to be a useful clinical tool in the monitoring of patients hospitalized after severe TBI in order to detect severe sleep deprivation requiring intervention. The direct impact of sleep-wake disturbances on physiological and cognitive recovery is not well understood within this population, but is worth investigating and improving.

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-016-0709-x) contains supplementary material, which is available to authorized users.

VTA dopaminergic neurons regulate ethologically relevant sleep-wake behaviors

Dopaminergic ventral tegmental area (VTA) neurons are critically involved in a variety of behaviors that rely on heightened arousal, but whether they directly and causally control the generation and maintenance of wakefulness is unknown. We recorded calcium activity using fiber photometry in freely behaving mice and found arousal-state-dependent alterations in VTA dopaminergic neurons. We used chemogenetic and optogenetic manipulations together with polysomnographic recordings to demonstrate that VTA dopaminergic neurons are necessary for arousal and that their inhibition suppresses wakefulness, even in the face of ethologically relevant salient stimuli. Nevertheless, before inducing sleep, inhibition of VTA dopaminergic neurons promoted goal-directed and sleep-related nesting behavior. Optogenetic stimulation, in contrast, initiated and maintained wakefulness and suppressed sleep and sleep-related nesting behavior. We further found that different projections of VTA dopaminergic neurons differentially modulate arousal. Collectively, our findings uncover a fundamental role for VTA dopaminergic circuitry in the maintenance of the awake state and ethologically relevant sleep-related behaviors.

Antipsychotic Drug-Induced Somnolence: Incidence, Mechanisms, and Management

Somnolence is a common side effect of antipsychotics. To assess the incidence of this side effect, we performed a MEDLINE search for randomized, double-blinded, placebo- or active-controlled studies of adult patients treated with antipsychotics for schizophrenia, mania, bipolar depression, or bipolar disorder. We extracted rates of somnolence from original publications and pooled them based on the dose of each antipsychotic in the same psychiatric condition, then estimated the absolute risk increase (ARI) and the number needed to harm (NNH) of an antipsychotic relative to placebo or an active comparator in the same psychiatric condition. According to the ARI in acute schizophrenia, bipolar mania, and bipolar depression, antipsychotics can be classified as high somnolence (clozapine), moderate somnolence (olanzapine, perphenazine, quetiapine, risperidone, ziprasidone), and low somnolence (aripiprazole, asenapine, haloperidol, lurasidone, paliperidone, cariprazine). The risk of somnolence with blonanserin, brexpiprazole, chlorpromazine, iloperidone, sertindole, and zotepine needs further investigation. The rates of somnolence were positively correlated to dose and duration for some antipsychotics, but not for others. Many factors, including antipsychotic per se, the method used to measure somnolence, patient population, study design, and dosing schedule, might affect the incidence of antipsychotic-induced somnolence. The mechanisms of antipsychotic-induced somnolence are likely multifactorial, although the blockade of histamine 1 receptors and α1 receptors may play a major role. The management of antipsychotic-induced somnolence should include sleep hygiene education, choosing an antipsychotic with a lower risk for somnolence, starting at a lower dose with a slower titration based on psychiatric diagnoses, adjusting doses when necessary, and minimizing concurrent somnolence-prone agents. Since most cases of somnolence were mild to moderate, allowing tolerance to develop over at least 4 weeks is reasonable before discontinuing an antipsychotic.

On-the-road driving performance after use of the antihistamines mequitazine and l-mequitazine, alone and with alcohol

OBJECTIVE

Previous studies demonstrated that mequitazine produces mild sedation after single doses. Its enantiomer, l-mequitazine, has a stronger potency for the H1 receptor. The aim of the current study was to assess the effects of l-mequitazine and mequitazine, alone and with alcohol, on driving.

METHODS

Twenty-five healthy volunteers were treated with l-mequitazine 2.5, 5.0 and 10 mg, mequitazine 10 mg and placebo, alone and in combination with alcohol in a double-blind crossover design. Driving performance was assessed using the standardized highway driving test in normal traffic. Its primary measure is the Standard Deviation of the Lateral Position (SDLP). Secondary measures consisted of an auditory word learning test during driving, and subjective measures of driving performance.

RESULTS

L-mequitazine 2.5 and 5.0 mg showed no effect on SDLP in the highway driving test, while SDLP significantly increased after l-mequitazine 10 mg (alone +1.59 cm; with alcohol +1.41 cm) and mequitazine 10 mg (with alcohol +1.17 cm). Alcohol significantly impaired all performance measures (SDLP +2.63 cm) but did not interact with the effects of treatment. Subjective measures indicated that participants were aware of the impairing effects of alcohol, but not of l-mequitazine and mequitazine.

CONCLUSION

L-mequitazine can be considered safe to drive in dosages of 2.5 and 5.0 mg. L-mequitazine 10 mg led to mild driving impairment. Alcohol impaired all performance measures and added to the effects of l-mequitazine and mequitazine.

Modulation of Total Sleep Time by Transcranial Direct Current Stimulation (tDCS)

Arousal and sleep are fundamental physiological processes, and their modulation is of high clinical significance. This study tested the hypothesis that total sleep time (TST) in humans can be modulated by the non-invasive brain stimulation technique transcranial direct current stimulation (tDCS) targeting a 'top-down' cortico-thalamic pathway of sleep-wake regulation. Nineteen healthy participants underwent a within-subject, repeated-measures protocol across five nights in the sleep laboratory with polysomnographic monitoring (adaptation, baseline, three experimental nights). tDCS was delivered via bi-frontal target electrodes and bi-parietal return electrodes before sleep (anodal 'activation', cathodal 'deactivation', and sham stimulation). Bi-frontal anodal stimulation significantly decreased TST, compared with cathodal and sham stimulation. This effect was location specific. Bi-frontal cathodal stimulation did not significantly increase TST, potentially due to ceiling effects in good sleepers. Exploratory resting-state EEG analyses before and after the tDCS protocols were consistent with the notion of increased cortical arousal after anodal stimulation and decreased cortical arousal after cathodal stimulation. The study provides proof-of-concept that TST can be decreased by non-invasive bi-frontal anodal tDCS in healthy humans. Further elucidating the 'top-down' pathway of sleep-wake regulation is expected to increase knowledge on the fundamentals of sleep-wake regulation and to contribute to the development of novel treatments for clinical conditions of disturbed arousal and sleep.

The anatomical, cellular and synaptic basis of motor atonia during rapid eye movement sleep

Rapid eye movement (REM) sleep is a recurring part of the sleep-wake cycle characterized by fast, desynchronized rhythms in the electroencephalogram (EEG), hippocampal theta activity, rapid eye movements, autonomic activation and loss of postural muscle tone (atonia). The brain circuitry governing REM sleep is located in the pontine and medullary brainstem and includes ascending and descending projections that regulate the EEG and motor components of REM sleep. The descending signal for postural muscle atonia during REM sleep is thought to originate from glutamatergic neurons of the sublaterodorsal nucleus (SLD), which in turn activate glycinergic pre-motor neurons in the spinal cord and/or ventromedial medulla to inhibit motor neurons. Despite work over the past two decades on many neurotransmitter systems that regulate the SLD, gaps remain in our knowledge of the synaptic basis by which SLD REM neurons are regulated and in turn produce REM sleep atonia. Elucidating the anatomical, cellular and synaptic basis of REM sleep atonia control is a critical step for treating many sleep-related disorders including obstructive sleep apnoea (apnea), REM sleep behaviour disorder (RBD) and narcolepsy with cataplexy.

A Review of Sleep and Its Disorders in Patients with Parkinson's Disease in Relation to Various Brain Structures

Sleep is an indispensable normal physiology of the human body fundamental for healthy functioning. It has been observed that Parkinson's disease (PD) not only exhibits motor symptoms, but also non-motor symptoms such as metabolic irregularities, altered olfaction, cardiovascular dysfunction, gastrointestinal complications and especially sleep disorders which is the focus of this review. A good understanding and knowledge of the different brain structures involved and how they function in the development of sleep disorders should be well comprehended in order to treat and alleviate these symptoms and enhance quality of life for PD patients. Therefore it is vital that the normal functioning of the body in relation to sleep is well understood before proceeding on to the pathophysiology of PD correlating to its symptoms. Suitable treatment can then be administered toward enhancing the quality of life of these patients, perhaps even discovering the cause for this disease.

Identification of proliferative progenitors associated with prominent postnatal growth of the pons

The pons controls crucial sensorimotor and autonomic functions. In humans, it grows sixfold postnatally and is a site of paediatric gliomas; however, the mechanisms of pontine growth remain poorly understood. We show that the murine pons quadruples in volume postnatally; growth is fastest during postnatal days 0–4 (P0–P4), preceding most myelination. We identify three postnatal proliferative compartments: ventricular, midline and parenchymal. We find no evidence of postnatal neurogenesis in the pons, but each progenitor compartment produces new astroglia and oligodendroglia; the latter expand 10- to 18-fold postnatally, and are derived mostly from the parenchyma. Nearly all parenchymal progenitors at P4 are Sox2⁺Olig2⁺, but by P8 a Sox2⁻ subpopulation emerges, suggesting a lineage progression from Sox2⁺ ‘early' to Sox2⁻ ‘late' oligodendrocyte progenitor. Fate mapping reveals that >90% of adult oligodendrocytes derive from P2–P3 Sox2⁺ progenitors. These results demonstrate the importance of postnatal Sox2⁺Olig2⁺ progenitors in pontine growth and oligodendrogenesis.

Postnatal growth of the pons is not well characterized. Here the authors show that growth of the murine pons is fastest during postnatal day 0–4, a period preceding myelination, and is primarily driven by an expansion of the oligodendrocyte population that derive from Sox2⁺Olig2⁺ progenitors.

Higher-protein diets improve indexes of sleep in energy-restricted overweight and obese adults: results from 2 randomized controlled trials

BACKGROUND

Limited and inconsistent research findings exist about the effect of dietary protein intake on indexes of sleep.

OBJECTIVE

We assessed the effect of protein intake during dietary energy restriction on indexes of sleep in overweight and obese adults in 2 randomized, controlled feeding studies.

DESIGN

For study 1, 14 participants [3 men and 11 women; mean ± SE age: 56 ± 3 y; body mass index (BMI; in kg/m(2)): 30.9 ± 0.6] consumed energy-restricted diets (a 750-kcal/d deficit) with either beef and pork (BP; n = 5) or soy and legume (SL; n = 9) as the main protein sources for 3 consecutive 4-wk periods with 10% (control), 20%, or 30% of total energy from protein (random order). At baseline and the end of each period, the global sleep score (GSS) was assessed with the use of the Pittsburgh Sleep Quality Index (PSQI) questionnaire. For study 2, 44 participants (12 men and 32 women; age: 52 ± 1 y; BMI: 31.4 ± 0.5) consumed a 3-wk baseline energy-balance diet with 0.8 g protein · kg baseline body mass(-1) · d(-1). Then, study 2 subjects consumed either a normal-protein [NP (control); n = 23] or a high-protein (HP; n = 21) (0.8 compared with 1.5 g · kg(-1) · d(-1), respectively) energy-restricted diet (a 750-kcal/d deficit) for 16 wk. The PSQI was administered during baseline week 3 and intervention weeks 4, 8, 12, and 16. GSSs ranged from 0 to 21 arbitrary units (au), with a higher value representing a worse GSS during the preceding month.

RESULTS

In study 1, we showed that a higher protein quantity improved GSSs independent of the protein source. The GSS was higher (P < 0.05) when 10% (6.0 ± 0.4 au) compared with 20% (5.0 ± 0.4 au) protein was consumed, with 30% protein (5.4 ± 0.6 au) intermediate. In study 2, at baseline, the GSS was not different between NP (5.2 ± 0.5 au) and HP (5.4 ± 0.5 au) groups. Over time, the GSS was unchanged for the NP group and improved for the HP group (P-group-by-time interaction < 0.05). After intervention (week 16), GSSs for NP and HP groups were 5.9 ± 0.5 and 4.0 ± 0.6 au, respectively (P < 0.01).

CONCLUSION

The consumption of a greater proportion of energy from protein while dieting may improve sleep in overweight and obese adults. This trial was registered at clinicaltrials.gov as NCT01005563 (study 1) and NCT01692860 (study 2).

Chronic sleep disturbance and neural injury: links to neurodegenerative disease

Sleep-wake disruption is frequently observed and often one of the earliest reported symptoms of many neurodegenerative disorders. This provides insight into the underlying pathophysiology of these disorders, as sleep-wake abnormalities are often accompanied by neurodegenerative or neurotransmitter changes. However, in addition to being a symptom of the underlying neurodegenerative condition, there is also emerging evidence that sleep disturbance itself may contribute to the development and facilitate the progression of several of these disorders. Due to its impact both as an early symptom and as a potential factor contributing to ongoing neurodegeneration, the sleep-wake cycle is an ideal target for further study for potential interventions not only to lessen the burden of these diseases but also to slow their progression. In this review, we will highlight the sleep phenotypes associated with some of the major neurodegenerative disorders, focusing on the circadian disruption associated with Alzheimer's disease, the rapid eye movement behavior disorder and sleep fragmentation associated with Parkinson's disease, and the insomnia and circadian dysregulation associated with Huntington's disease.

Control of Sleep by Dopaminergic Inputs to the Drosophila Mushroom Body

The Drosophila mushroom body (MB) is an associative learning network that is important for the control of sleep. We have recently identified particular intrinsic MB Kenyon cell (KC) classes that regulate sleep through synaptic activation of particular MB output neurons (MBONs) whose axons convey sleep control signals out of the MB to downstream target regions. Specifically, we found that sleep-promoting KCs increase sleep by preferentially activating cholinergic sleep-promoting MBONs, while wake-promoting KCs decrease sleep by preferentially activating glutamatergic wake-promoting MBONs. Here we use a combination of genetic and physiological approaches to identify wake-promoting dopaminergic neurons (DANs) that innervate the MB, and show that they activate wake-promoting MBONs. These studies reveal a dopaminergic sleep control mechanism that likely operates by modulation of KC-MBON microcircuits.

Sleep-Wake Cycle Dysfunction in the TgCRND8 Mouse Model of Alzheimer's Disease: From Early to Advanced Pathological Stages

In addition to cognitive decline, individuals affected by Alzheimer’s disease (AD) can experience important neuropsychiatric symptoms including sleep disturbances. We characterized the sleep-wake cycle in the TgCRND8 mouse model of AD, which overexpresses a mutant human form of amyloid precursor protein resulting in high levels of β-amyloid and plaque formation by 3 months of age. Polysomnographic recordings in freely-moving mice were conducted to study sleep-wake cycle architecture at 3, 7 and 11 months of age and corresponding levels of β-amyloid in brain regions regulating sleep-wake states were measured. At all ages, TgCRND8 mice showed increased wakefulness and reduced non-rapid eye movement (NREM) sleep during the resting and active phases. Increased wakefulness in TgCRND8 mice was accompanied by a shift in the waking power spectrum towards fast frequency oscillations in the beta (14-20 Hz) and low gamma range (20-50 Hz). Given the phenotype of hyperarousal observed in TgCRND8 mice, the role of noradrenergic transmission in the promotion of arousal, and previous work reporting an early disruption of the noradrenergic system in TgCRND8, we tested the effects of the alpha-1-adrenoreceptor antagonist, prazosin, on sleep-wake patterns in TgCRND8 and non-transgenic (NTg) mice. We found that a lower dose (2 mg/kg) of prazosin increased NREM sleep in NTg but not in TgCRND8 mice, whereas a higher dose (5 mg/kg) increased NREM sleep in both genotypes, suggesting altered sensitivity to noradrenergic blockade in TgCRND8 mice. Collectively our results demonstrate that amyloidosis in TgCRND8 mice is associated with sleep-wake cycle dysfunction, characterized by hyperarousal, validating this model as a tool towards understanding the relationship between β-amyloid overproduction and disrupted sleep-wake patterns in AD.

Esmirtazapine in non-elderly adult patients with primary insomnia: efficacy and safety from a randomized, 6-week sleep laboratory trial

OBJECTIVE

Esmirtazapine (Org 50081), a medication that binds with high affinity to serotonin 5-HT2A and histamine-1 receptors, was evaluated as a potential treatment for insomnia.

METHODS

Adults with primary insomnia were treated with esmirtazapine (3.0 or 4.5 mg) or placebo in this 6-week, double-blind, randomized, polysomnography (PSG) study. The end points included wake time after sleep onset (WASO) (primary), latency to persistent sleep, and total sleep time. Patient-reported parameters were also evaluated, including sleep quality and satisfaction with sleep duration. Residual daytime effects and rebound insomnia (sleep parameters during the single-blind placebo run-out week after treatment ended) were also assessed.

RESULTS

Overall, 419 patients were randomized and 366 (87%) completed treatment. The median decrease in PSG WASO (double-blind average) was 20.5 min for placebo, and 52.0 min and 53.6 min for the 3.0- and 4.5-mg esmirtazapine groups, respectively (P < 0.0001 vs. placebo for both doses). Changes in the other PSG parameters and in all patient-reported parameters were also statistically significant with both doses versus placebo. Overall, 35-42% of esmirtazapine-treated patients had adverse events (AEs) versus 29% in the placebo group. AEs were mild or moderate in most esmirtazapine-treated patients. Furthermore, the incidence of AEs leading to discontinuation was low (<8%).

CONCLUSIONS

Six weeks of treatment with esmirtazapine was associated with consistent improvements in objective and patient-reported parameters of sleep onset, maintenance, and duration. It was generally well tolerated, and residual daytime effects were minimal and no rebound insomnia was observed.

Sleep influences the intracerebral EEG pattern of focal cortical dysplasia

OBJECTIVE

Focal cortical dysplasia (FCD) is able to generate an intrinsic pathological EEG activity characterized by a continuous or near-continuous spiking. Different patterns of discharge were described. We examined quantitatively the distribution of the intracerebral FCD patterns in relation to sleep in order to investigate whether this activity is independent of thalamocortical influences.

METHODS

We analyzed the first sleep cycle of 5 patients with a diagnosis of FCD type II who underwent combined scalp-intracranial electroencephalography (EEG), and showed an intracranial EEG pattern typical for FCD. Three patterns of FCD intracranial EEG activity were identified in all 5 patients, and visually marked for a maximum of 30min of each stage (wake, N1, N2, N3, REM): spike or polyspike exceeding 2Hz (pattern 1), spike or polyspike interrupted by flat periods below 2Hz (pattern 2) and discharges of >15Hz low-voltage rhythmic activity with regular morphology (pattern 3). After marking, the percentages of the three patterns across the different stages were calculated.

RESULTS

The three patterns of FCD were present between 45% and 97% of the total time analyzed. Pattern 1 was the predominant pattern in wakefulness (73-100%), N1 (76-97%) and N2 (58-88.5%) in all patients, and in REM in 4 of 5 patients (91-100%). During N2 and N3, there was an increase in pattern 2 in all patients, becoming the predominant pattern in 3 of the 5 patients during N3 (63-89%). Pattern 3 was rare and only sporadically observed during N2 and N3. Wakefulness and REM sleep showed a similar pattern (pattern 1) with a slight amplitude reduction in REM sleep.

SIGNIFICANCE

Despite the presence of an almost continuous discharge, sleep is an important modulator of the pathological EEG patterns found in FCD type II. This might suggest that dysplastic tissue is influenced by the thalamo-cortical control mechanisms involved in the generation of sleep.

Neuropeptidergic control of sleep and wakefulness

Sleep and wake are fundamental behavioral states whose molecular regulation remains mysterious. Brain states and body functions change dramatically between sleep and wake, are regulated by circadian and homeostatic processes, and depend on the nutritional and emotional condition of the animal. Sleep-wake transitions require the coordination of several brain regions and engage multiple neurochemical systems, including neuropeptides. Neuropeptides serve two main functions in sleep-wake regulation. First, they represent physiological states such as energy level or stress in response to environmental and internal stimuli. Second, neuropeptides excite or inhibit their target neurons to induce, stabilize, or switch between sleep-wake states. Thus, neuropeptides integrate physiological subsystems such as circadian time, previous neuron usage, energy homeostasis, and stress and growth status to generate appropriate sleep-wake behaviors. We review the roles of more than 20 neuropeptides in sleep and wake to lay the foundation for future studies uncovering the mechanisms that underlie the initiation, maintenance, and exit of sleep and wake states.

Treatment paradigms for cataplexy in narcolepsy: past, present, and future

Cataplexy is defined as episodes of sudden loss of voluntary muscle tone triggered by emotions generally lasting <2 minutes. Cataplexy is most commonly associated with and considered pathognomonic for narcolepsy, a sleep disorder affecting ~0.05% of the general population. Knowledge of the pathophysiology of cataplexy has advanced through study of canine, murine, and human models. It is now generally considered that loss of signaling by hypothalamic hypocretin/orexin-producing neurons plays a key role in the development of cataplexy. Although the cause of hypocretin/orexin neuron loss in narcolepsy with cataplexy is unknown, an autoimmune etiology is widely hypothesized. Despite these advances, a literature review shows that treatment of cataplexy remains limited. Multiple classes of antidepressants have been commonly used off-label for cataplexy in narcolepsy and are suggested for this use in expert consensus guidelines based on traditional practice, case reports, and small trials. However, systematic research evidence supporting antidepressants for cataplexy is lacking. The single pharmacotherapy indicated for cataplexy and the guideline-recommended first-line treatment in Europe and the US is sodium oxybate, the sodium salt of gamma-hydroxybutyrate. Clinical trial evidence of its efficacy and safety in cataplexy is robust, and it is hypothesized that its therapeutic effects may occur through gamma-aminobutyric acid receptor type B-mediated effects at noradrenergic, dopaminergic, and thalamocortical neurons. Additional possible mechanisms for cataplexy therapy suggested by preliminary research include antagonism of the histamine H3 autoreceptor with pitolisant and intravenous immunoglobulin therapy for amelioration of the presumed autoimmune-mediated hypocretin/orexin cell loss. Further research and development of therapeutic approaches to cataplexy are needed.

Cortical network switching: possible role of the lateral septum and cholinergic arousal

BACKGROUND

Cortical networks undergo large-scale switching between states of increased or decreased activity in normal sleep and cognition as well as in pathological conditions such as epilepsy. We previously found that focal hippocampal seizures in rats induce increased neuronal firing and cerebral blood flow in subcortical structures including the lateral septal area, along with frontal cortical slow oscillations resembling slow wave sleep. In addition, stimulation of the lateral septum in the absence of a seizure resulted in cortical deactivation with slow oscillations.

HYPOTHESIS

We hypothesized that lateral septal activation might cause neocortical deactivation indirectly, possibly through impaired subcortical arousal. But how does subcortical stimulation cause slow wave activity in frontal cortex? How do arousal neurotransmitter levels (e.g. acetylcholine) change in cortex during the excitation of inhibitory projection nuclei?

METHODS AND RESULTS

In the current study, we used simultaneous electrophysiology and enzyme-based amperometry in a rat model, and found a decrease in choline, along with slow wave activity in orbital frontal cortex during lateral septal stimulation in the absence of seizures. In contrast, the choline signal and local field potential in frontal cortex had no significant changes when stimulating the hippocampus, but showed increased choline and decreased slow wave activity with an arousal stimulus produced by toe pinch.

CONCLUSIONS

These findings indicate that the activation of subcortical inhibitory structures (such as lateral septum) can depress subcortical cholinergic arousal. This mechanism may play an important role in large-scale transitions of cortical activity in focal seizures, as well as in normal cortical function.

Sleep and respiratory physiology in adults

Respiration during sleep is determined by metabolic demand; respiratory drive is determined by a central respiratory generator. Changes in pharyngeal dilator muscle tone resulting in increased upper airway resistance and collapsibility contribute to hypoventilation. Relative hypotonia of respiratory muscles, body posture changes, and altered ventilatory control result in additional physiologic changes contributing to hypoventilation. This article reviews mechanisms of central control of respiration and normal upper and lower airway physiology. Understanding sleep-related changes in respiratory physiology will help in developing new therapies to prevent hypoventilation in susceptible populations.

What optogenetic stimulation is telling us (and failing to tell us) about fast neurotransmitters and neuromodulators in brain circuits for wake-sleep regulation

In the last eight years optogenetic tools have been widely used to identify functional synaptic connectivity between specific neuronal populations. Most of our knowledge comes from the photo-activation of channelrhodopsin-2 (ChR2) expressing inputs that release glutamate and GABA. More recent studies have been reporting releases of acetylcholine and biogenic amines but direct evidence for photo-evoked released of neuropeptides is still limited particularly in brain slice studies. The high fidelity in the responses with photo-evoked amino-acid transmission is ideal for ChR2-assisted circuit mapping and this approach has been successfully used in different fields of neuroscience. Conversely, neuropeptides employ a slow mode of communication and might require higher frequency and prolonged stimulations to be released. These factors may have contributed to the apparent lack of success for optogenetic release of neuropeptides. In addition, once released, neuropeptides often act on multiple sites and at various distances from the site of release resulting in a greater complexity of postsynaptic responses. Here, we focus on what optogenetics is telling us-and failing to tell us-about fast neurotransmitters and neuropeptides.

Sleep disturbance, depression and pain in adults with sickle cell disease

BACKGROUND

Sleep disturbance and depression are commonly encountered in primary care. In sickle cell disease, depression is associated with pain, poor treatment compliance, and lower quality of life. The prevalence of sleep disturbance and its effect upon quality of life in adults with sickle cell disease is unknown. The goal of this study was to determine the prevalence of sleep disturbance and if it is associated with pain and depression in sickle cell disease.

METHODS

Three hundred twenty eight adults with sickle cell disease enrolled on the Bethesda Sickle Cell Cohort Study were assessed using the Pittsburgh Sleep Quality Index and Beck Depression Inventory II screening measures as a cross-sectional survey. Scores greater than 5 (Pittsburgh Sleep Quality Index) and 16 (Beck Depression Inventory II) defined sleep disturbance and depression, respectively. Clinical and laboratory parameters were also assessed.

RESULTS

The mean Pittsburgh Sleep Quality Index score was 8.4 (SD ± 4.2) indicating a 71.2% prevalence of sleep disturbance. The mean Beck Depression Inventory II score was 8.0 (SD ± 8.9). Sixty five (20.6%) participants had a score indicating depression, and half of these (10.0%) had thoughts of suicide. Both Pittsburgh Sleep Quality Index and Beck Depression Inventory II scores were significantly correlated (p < .001). The number of days with mild/moderate pain (p = .001) and a history of headaches (p = .005) were independently associated with depression by multivariate regression analysis. Patients with sleep disturbance were older (p = .002), had higher body mass index (p = .011), had more days of pain (p = .003) and more frequent severe acute painful events (emergency room visits and hospitalizations) during the previous 12 months (p < .001).

CONCLUSIONS

More than 70 percent of adults with sickle cell disease had sleep disturbance, while 21 percent showed evidence of clinical depression. Sleep disturbance and depression were correlated, and were most common among those with more frequent pain. Providers caring for adults with sickle cell disease and frequent pain should consider screening for these common co-morbidities. Additional study is needed to confirm these findings and to determine if treatments for pain, depression or sleep disturbances will improve quality of life measures in this patient population.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00011648.

Optogenetic stimulation of locus ceruleus neurons augments inhibitory transmission to parasympathetic cardiac vagal neurons via activation of brainstem α1 and β1 receptors

Locus ceruleus (LC) noradrenergic neurons are critical in generating alertness. In addition to inducing cortical arousal, the LC also orchestrates changes in accompanying autonomic system function that compliments increased attention, such as during stress, excitation, and/or exposure to averse or novel stimuli. Although the association between arousal and increased heart rate is well accepted, the neurobiological link between the LC and parasympathetic neurons that control heart rate has not been identified. In this study, we test directly whether activation of noradrenergic neurons in the LC influences brainstem parasympathetic cardiac vagal neurons (CVNs). CVNs were identified in transgenic mice that express channel-rhodopsin-2 (ChR2) in LC tyrosine hydroxylase neurons. Photoactivation evoked a rapid depolarization, increased firing, and excitatory inward currents in ChR2-expressing neurons in the LC. Photostimulation of LC neurons did not alter excitatory currents, but increased inhibitory neurotransmission to CVNs. Optogenetic activation of LC neurons increased the frequency of isolated glycinergic IPSCs by 27 ± 8% (p = 0.003, n = 26) and augmented GABAergic IPSCs in CVNs by 21 ± 5% (p = 0.001, n = 26). Inhibiting α1, but not α2, receptors blocked the evoked responses. Inhibiting β1 receptors prevented the increase in glycinergic, but not GABAergic, IPSCs in CVNs. This study demonstrates LC noradrenergic neurons inhibit the brainstem CVNs that generate parasympathetic activity to the heart. This inhibition of CVNs would increase heart rate and risks associated with tachycardia. The receptors activated within this pathway, α1 and/or β1 receptors, are targets for clinically prescribed antagonists that promote slower, cardioprotective heart rates during heightened vigilant states.

Why does sleep stop migraine?

The relationship between sleep and migraine headaches is complex. Changes in sleep patterns can trigger migraine attacks, and sleep disorders may be associated with increased migraine frequency. Furthermore, migraine patients and their doctors very consistently report that sleep relieves already established migraine attacks. Herein we will try to answer the question, "Why does sleep stop migraine?" Since evidence for this relationship is largely based on empirical clinical observation, we will not provide a clinical review of the association. Instead, we will focus on the pathophysiology of migraine attacks and its intersections with sleep biology.

Principles of medicating children with neurodevelopmental and sleep disorders--a review

Conflict between the demands of the environment in which a child lives and the child's intrinsic sleep signature, produces stress-behaviour difficulties in the child. Distorted development, especially distorted brain development, often leads to distorted intrinsic sleep signatures. The sleep-behaviour outcome, arising from the conflict between each child's sleep signature and the environmental niche in which they live, can be modified by medications, on the one hand, and taking the role of kin, peer and social networks seriously. Medications alter the intrinsic sleep signature of the child and the stress response. Non-medical interventions address the demands and constraints of the child's environmental niche. When the main medication strategy to address distorted sleep involves brain stimulation, those children that do not respond will often need a reversal of medication priorities; an inhibitory strategy as a short to medium term support, sleep regulation being primary for longer term management, and stimulatory strategies used sparingly, if at all. We are often dealing with vulnerable populations, not all of which are reliable or accurate sources of information. Features of a presentation alerting the clinician to non-medication factors contributing to the failure of treatment are discussed.

Neuroticism relates to daytime wakefulness and sleep devaluation via high neurophysiological efficiency in the bilateral prefrontal cortex: a preliminary study

Higher wake promotion against sleep drive boosts cognitive processing, but it also seems to increase the risk of insomnia by reinforcing an obsession with sleep in neurotic patients. To explore whether a personality trait of neuroticism simultaneously facilitates wake-promoting ability and sleep devaluation via a common regional prefrontal function under a sleep-restricted condition, working memory tasks were administered to 49 healthy humans after a 2-h sleep restriction. Higher wake-promoting ability demonstrated in a high-load task was correlated with lower bilateral prefrontal activation, as measured by near-infrared spectroscopy. Structural equation modeling revealed that neuroticism predicts sleep devaluation and wake-promoting ability via left and right regional prefrontal efficiency, respectively. Our results indicate that neuroticism-related neural efficiency increases resilience to sleepiness, but decreases sleep satisfaction.

Approach to insomnia in patients with dementia

Insomnia occurs in one-fourth to one-third of patients with dementia, and can lead to patient and caretaker distress and early institutionalization. An array of effects from the disease, medication, behaviors, and mood issues may play a role in influencing sleep. This perplexing issue can be handled effectively with appropriate evaluation and understanding of basic sleep-wake physiology. For most patients, appropriate timing of cues, modifying behavior, and optimizing medications can improve the patient's and caregiver's quality of life. In this article, we review signs that may help the clinician recognize insomnia early and approach the issue in a logical manner.

Alcohol and the sleeping brain

Alcohol acts as a sedative that interacts with several neurotransmitter systems important in the regulation of sleep. Acute administration of large amounts of alcohol prior to sleep leads to decreased sleep-onset latency and changes in sleep architecture early in the night, when blood alcohol levels are high, with subsequent disrupted, poor-quality sleep later in the night. Alcohol abuse and dependence are associated with chronic sleep disturbance, lower slow-wave sleep, and more rapid-eye-movement sleep than normal, that last long into periods of abstinence and may play a role in relapse. This chapter outlines the evidence for acute and chronic alcohol effects on sleep architecture and sleep electroencephalogram, evidence for tolerance with repeated administration, and possible underlying neurochemical mechanisms for alcohol's effects on sleep. Also discussed are sex differences as well as effects of alcohol on sleep homeostasis and circadian regulation. Evidence for the role of sleep disruption as a risk factor for developing alcohol dependence is discussed in the context of research conducted in adolescents. The utility of sleep-evoked potentials in the assessment of the effects of alcoholism on sleep and the brain and in abstinence-mediated recovery is also outlined. The chapter concludes with a series of questions that need to be answered to determine the role of sleep and sleep disturbance in the development and maintenance of problem drinking and the potential beneficial effects of the treatment of sleep disorders for maintenance of abstinence in alcoholism.

Olanzapine and clozapine differently affect sleep in patients with schizophrenia: results from a double-blind, polysomnographic study and review of the literature

Schizophrenia is associated with impaired sleep continuity. The second generation antipsychotics clozapine and olanzapine have been reported to improve sleep continuity but also to rarely induce restless legs syndrome (RLS). The aims of this randomized double-blind study were to compare the effects of clozapine and olanzapine on sleep and the occurrence of RLS. Therefore, polysomnographies were recorded and RLS symptoms were assessed in 30 patients with schizophrenia before and after 2, 4 and 6 weeks of treatment with either clozapine or olanzapine. Treatment with both antipsychotics increased total sleep time, sleep period time and sleep efficiency and decreased sleep onset latency. These changes were similar in both groups, occurred during the first 2 treatment weeks and were sustained. For example, sleep efficiency increased from 83% (olanzapine) and 82% (clozapine) at baseline to 95% at week 2 and 97% at week 6 in both treatment groups. Sleep architecture was differently affected: clozapine caused a significantly stronger increase of stage 2 sleep (44%) than olanzapine (11%) but olanzapine a significantly stronger increase of REM-sleep. Olanzapine caused an 80% increase of slow wave sleep whereas clozapine caused a 6% decrease. No patient reported any of 4 RLS defining symptoms at baseline. During treatment, 1 patient of each group reported at one visit all 4 symptoms, i.e. met the diagnosis of an RLS. In conclusion, sleep continuity similarly improved and sleep architecture changed more physiologically with olanzapine. Neither of the antipsychotics induced RLS symptoms that were clinically relevant.

Set and setting: how behavioral state regulates sensory function and plasticity

Recently developed neuroimaging and electrophysiological techniques are allowing us to answer fundamental questions about how behavioral states regulate our perception of the external environment. Studies using these techniques have yielded surprising insights into how sensory processing is affected at the earliest stages by attention and motivation, and how new sensory information received during wakefulness (e.g., during learning) continues to affect sensory brain circuits (leading to plastic changes) during subsequent sleep. This review aims to describe how brain states affect sensory response properties among neurons in primary and secondary sensory cortices, and how this relates to psychophysical detection thresholds and performance on sensory discrimination tasks. This is not intended to serve as a comprehensive overview of all brain states, or all sensory systems, but instead as an illustrative description of how three specific state variables (attention, motivation, and vigilance [i.e., sleep vs. wakefulness]) affect sensory systems in which they have been best studied.

Effects of rotigotine on Parkinson's disease-related sleep disturbances

INTRODUCTION

Sleep abnormalities are a frequent non-motor symptom and a prominent cause of disability in patients with Parkinson's disease (PD).

AREAS COVERED

This review discusses what is currently known about the characteristics of sleep disturbances in PD patients and attempts to clarify the role of dopaminergic pathways in their pathogenesis as well as the beneficial effect of dopaminergic agents in their treatment. In particular, this review will focus on the effects of transdermal rotigotine on improving PD-related sleep disorders.

EXPERT OPINION

Sleep disturbances are common in PD, and these disturbances can be reduced or resolved, in large part, by preventing or attenuating nocturnal and early morning motor and non-motor symptoms of PD. The studies discussed within this review suggest that sleep disorders are not just a consequence of motor impairment and dopaminergic therapy but are an integral part of the neurodegenerative process of PD. This is supported by the appearance of specific sleep disturbances, which are related to degeneration of the brainstem areas involved in the regulation of sleep/wake states in advance of typical PD symptoms. Development of more detailed diagnostic tools aimed at detecting sleep disturbances and at defining the main causative factors of sleep disturbances in PD will lead to improved treatment of these disturbances.

Orexin receptor antagonists differ from standard sleep drugs by promoting sleep at doses that do not disrupt cognition

Current treatments for insomnia, such as zolpidem (Ambien) and eszopiclone (Lunesta), are γ-aminobutyric acid type A (GABAA)-positive allosteric modulators that carry a number of side effects including the potential to disrupt cognition. In an effort to develop better tolerated medicines, we have identified dual orexin 1 and 2 receptor antagonists (DORAs), which promote sleep in preclinical animal models and humans. We compare the effects of orally administered eszopiclone, zolpidem, and diazepam to the dual orexin receptor antagonist DORA-22 on sleep and the novel object recognition test in rat, and on sleep and two cognition tests (delayed match to sample and serial choice reaction time) in the rhesus monkey. Each compound's minimal dose that promoted sleep versus the minimal dose that exerted deficits in these cognitive tests was determined, and a therapeutic margin was established. We found that DORA-22 has a wider therapeutic margin for sleep versus cognitive impairment in rat and rhesus monkey compared to the other compounds tested. These data were further supported with the demonstration of a wider therapeutic margin for DORA-22 compared to the other compounds on sleep versus the expression of hippocampal activity-regulated cytoskeletal-associated protein (Arc), an immediate-early gene product involved in synaptic plasticity. These findings suggest that DORAs might provide an effective treatment for insomnia with a greater therapeutic margin for sleep versus cognitive disturbances compared to the GABAA-positive allosteric modulators currently in use.

The duration of sleep promoting efficacy by dual orexin receptor antagonists is dependent upon receptor occupancy threshold

Background

Drugs targeting insomnia ideally promote sleep throughout the night, maintain normal sleep architecture, and are devoid of residual effects associated with morning sedation. These features of an ideal compound are not only dependent upon pharmacokinetics, receptor binding kinetics, potency and pharmacodynamic activity, but also upon a compound’s mechanism of action.

Results

Dual orexin receptor antagonists (DORAs) block the arousal-promoting activity of orexin peptides and, as demonstrated in the current work, exhibit an efficacy signal window dependent upon oscillating levels of endogenous orexin neuropeptide. Sleep efficacy of structurally diverse DORAs in rat and dog was achieved at plasma exposures corresponding to orexin 2 receptor (OX₂R) occupancies in the range of 65 to 80%. In rats, the time course of OX₂R occupancy was dependent upon receptor binding kinetics and was tightly correlated with the timing of active wake reduction. In rhesus monkeys, direct comparison of DORA-22 with GABA-A modulators at similar sleep-inducing doses revealed that diazepam produced next-day residual sleep and both diazepam and eszopiclone induced next-day cognitive deficits. In stark contrast, DORA-22 did not produce residual effects. Furthermore, DORA-22 evoked only minimal changes in quantitative electroencephalogram (qEEG) activity during the normal resting phase in contrast to GABA-A modulators which induced substantial qEEG changes.

Conclusion

The higher levels of receptor occupancy necessary for DORA efficacy require a plasma concentration profile sufficient to maintain sleep for the duration of the resting period. DORAs, with a half-life exceeding 8 h in humans, are expected to fulfill this requirement as exposures drop to sub-threshold receptor occupancy levels prior to the wake period, potentially avoiding next-day residual effects at therapeutic doses.