Insights from studying human sleep disorders

Review of somatic symptoms in post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is associated with both (1) 'ill-defined' or 'medically unexplained' somatic syndromes, e.g. unexplained dizziness, tinnitus and blurry vision, and syndromes that can be classified as somatoform disorders (DSM-IV-TR); and (2) a range of medical conditions, with a preponderance of cardiovascular, respiratory, musculoskeletal, neurological, and gastrointestinal disorders, diabetes, chronic pain, sleep disorders and other immune-mediated disorders in various studies. Frequently reported medical co-morbidities with PTSD across various studies include cardiovascular disease, especially hypertension, and immune-mediated disorders. PTSD is associated with limbic instability and alterations in both the hypothalamic- pituitary-adrenal and sympatho-adrenal medullary axes, which affect neuroendocrine and immune functions, have central nervous system effects resulting in pseudo-neurological symptoms and disorders of sleep-wake regulation, and result in autonomic nervous system dysregulation. Hypervigilance, a central feature of PTSD, can lead to 'local sleep' or regional arousal states, when the patient is partially asleep and partially awake, and manifests as complex motor and/or verbal behaviours in a partially conscious state. The few studies of the effects of standard PTSD treatments (medications, CBT) on PTSD-associated somatic syndromes report a reduction in the severity of ill-defined and autonomically mediated somatic symptoms, self-reported physical health problems, and some chronic pain syndromes.

The parasomnias: mechanisms and treatment

Although parasomnias should be considered benign conditions without a deleterious impact on sleep quality and quantity, especially in children, it is important to recognize and properly diagnose these phenomena. Moreover, parasomnias may be misdiagnosed as epileptic seizures, in particular seizures with a predominant complex motor behavior as seizures occurring in nocturnal frontal lobe epilepsy (NFLE), leading to unnecessary and expensive investigations and prolonged and unsuccessful treatment. In this article we describe the clinical and neurophysiologic features of the most common parasomnias, giving the most reliable elements of differential diagnosis between parasomnias and epileptic nocturnal seizures, namely the typical seizures occurring in NFLE. The diagnostic value of history-taking, video-polysomnography, home video recording, and diagnostic scales is discussed. Next we describe the intriguing aspect of the frequent coexistence, in the same family and even in the same patients, of epileptic and parasomniac attacks, giving a common neurophysiologic interpretation. Finally some brief indications to the treatment of parasomnias are suggested.

Neuromodulation of brain states

Switches between different behavioral states of the animal are associated with prominent changes in global brain activity, between sleep and wakefulness or from inattentive to vigilant states. What mechanisms control brain states, and what are the functions of the different states? Here we summarize current understanding of the key neural circuits involved in regulating brain states, with a particular emphasis on the subcortical neuromodulatory systems. At the functional level, arousal and attention can greatly enhance sensory processing, whereas sleep and quiet wakefulness may facilitate learning and memory. Several new techniques developed over the past decade promise great advances in our understanding of the neural control and function of different brain states.

A transition-constrained discrete hidden Markov model for automatic sleep staging

BACKGROUND

Approximately one-third of the human lifespan is spent sleeping. To diagnose sleep problems, all-night polysomnographic (PSG) recordings including electroencephalograms (EEGs), electrooculograms (EOGs) and electromyograms (EMGs), are usually acquired from the patient and scored by a well-trained expert according to Rechtschaffen & Kales (R&K) rules. Visual sleep scoring is a time-consuming and subjective process. Therefore, the development of an automatic sleep scoring method is desirable.

METHOD

The EEG, EOG and EMG signals from twenty subjects were measured. In addition to selecting sleep characteristics based on the 1968 R&K rules, features utilized in other research were collected. Thirteen features were utilized including temporal and spectrum analyses of the EEG, EOG and EMG signals, and a total of 158  hours of sleep data were recorded. Ten subjects were used to train the Discrete Hidden Markov Model (DHMM), and the remaining ten were tested by the trained DHMM for recognition. Furthermore, the 2-fold cross validation was performed during this experiment.

RESULTS

Overall agreement between the expert and the results presented is 85.29%. With the exception of S1, the sensitivities of each stage were more than 81%. The most accurate stage was SWS (94.9%), and the least-accurately classified stage was S1 (<34%). In the majority of cases, S1 was classified as Wake (21%), S2 (33%) or REM sleep (12%), consistent with previous studies. However, the total time of S1 in the 20 all-night sleep recordings was less than 4%.

CONCLUSION

The results of the experiments demonstrate that the proposed method significantly enhances the recognition rate when compared with prior studies.

Identification of the transmitter and receptor mechanisms responsible for REM sleep paralysis

During REM sleep the CNS is intensely active, but the skeletal motor system is paradoxically forced into a state of muscle paralysis. The mechanisms that trigger REM sleep paralysis are a matter of intense debate. Two competing theories argue that it is caused by either active inhibition or reduced excitation of somatic motoneuron activity. Here, we identify the transmitter and receptor mechanisms that function to silence skeletal muscles during REM sleep. We used behavioral, electrophysiological, receptor pharmacology and neuroanatomical approaches to determine how trigeminal motoneurons and masseter muscles are switched off during REM sleep in rats. We show that a powerful GABA and glycine drive triggers REM paralysis by switching off motoneuron activity. This drive inhibits motoneurons by targeting both metabotropic GABA(B) and ionotropic GABA(A)/glycine receptors. REM paralysis is only reversed when motoneurons are cut off from GABA(B), GABA(A) and glycine receptor-mediated inhibition. Neither metabotropic nor ionotropic receptor mechanisms alone are sufficient for generating REM paralysis. These results demonstrate that multiple receptor mechanisms trigger REM sleep paralysis. Breakdown in normal REM inhibition may underlie common sleep motor pathologies such as REM sleep behavior disorder.

Control of sleep and wakefulness

This review summarizes the brain mechanisms controlling sleep and wakefulness. Wakefulness promoting systems cause low-voltage, fast activity in the electroencephalogram (EEG). Multiple interacting neurotransmitter systems in the brain stem, hypothalamus, and basal forebrain converge onto common effector systems in the thalamus and cortex. Sleep results from the inhibition of wake-promoting systems by homeostatic sleep factors such as adenosine and nitric oxide and GABAergic neurons in the preoptic area of the hypothalamus, resulting in large-amplitude, slow EEG oscillations. Local, activity-dependent factors modulate the amplitude and frequency of cortical slow oscillations. Non-rapid-eye-movement (NREM) sleep results in conservation of brain energy and facilitates memory consolidation through the modulation of synaptic weights. Rapid-eye-movement (REM) sleep results from the interaction of brain stem cholinergic, aminergic, and GABAergic neurons which control the activity of glutamatergic reticular formation neurons leading to REM sleep phenomena such as muscle atonia, REMs, dreaming, and cortical activation. Strong activation of limbic regions during REM sleep suggests a role in regulation of emotion. Genetic studies suggest that brain mechanisms controlling waking and NREM sleep are strongly conserved throughout evolution, underscoring their enormous importance for brain function. Sleep disruption interferes with the normal restorative functions of NREM and REM sleep, resulting in disruptions of breathing and cardiovascular function, changes in emotional reactivity, and cognitive impairments in attention, memory, and decision making.

Parasomnias and nocturnal frontal lobe epilepsy (NFLE): lights and shadows--controversial points in the differential diagnosis

Nocturnal frontal lobe epilepsy (NFLE) is characterized by seizures with complex, often bizarre, violent behaviour arising only or mainly during sleep. These unusual seizures and their occurrence during sleep are often accompanied by normal EEG tracings and neuroradiological findings, making it difficult to distinguish NFLE seizures from other non-epileptic nocturnal paroxysmal events, namely parasomnias. NFLE was described for the first time in 1981, but, as its epileptic origin was controversial, the condition was called nocturnal paroxysmal dystonia. Even though many aspects of parasomnias and NFLE have been clarified in the last two decades, the problem of differential diagnosis remains a challenge for clinicians. This paper discusses some controversial points still under debate. The difficulties in distinguishing nocturnal epileptic seizures from parasomnias reflect just one aspect of the intriguing issue of the pathophysiological relationships between all types of paroxysmal motor behaviours during sleep.

From REM sleep behaviour disorder to status dissociatus: insights into the maze of states of being

Sleep is a coordinated process involving more or less simultaneous changes in sensory, motor, autonomic, hormonal, and cerebral processes. On the other hand, none of the changes occurring with sleep are invariably coupled to sleep. EEG synchrony, heat loss, sleep-related hormone secretion, and even REM-related motoneuron paralysis may occur independent of the parent state. In REM sleep behaviour disorder (RBD) the muscle tone of wakefulness intrudes into REM sleep, allowing the release of dream-enacting behaviours. Status dissociatus (SD) is a condition in which brain and mind are in disarray along the boundaries of sleep and wakefulness. The existence of such dissociated behaviours shows that they have separate neuronal control systems and indicates that the whole organization of sleep is an emergent property of the collective neuronal systems to synchronize. Insults to the brain can drastically alter the circuitries responsible for maintaining the integrity of wakefulness, NREM sleep, and REM sleep. As a consequence, the basic states of existence can become admixed and interchanged with striking disturbances of consciousness, brain electrophysiology, and the behavioural and polygraphic expression of sleep and wakefulness. The evolution of RBD into SD may result from a disarray of (brainstem) structures that orchestrate the whole brain wake-sleep conditions, but with preserved discrete systems and dissociable strategies to still place navigation in wake and sleep. Advances in the fields of genetics, neuroimaging, and behavioural neurology will expand the understanding of the mechanisms underlying the organization of the states of being along with their somatic/behavioural manifestations.

When Parkinson's disease patients go to sleep: specific sleep disturbances related to Parkinson's disease

Nonmotor symptoms of Parkinson's disease can be as disabling as the much better studied motor symptoms. Among the nonmotor manifestations are numerous forms of alterations of physiologic sleep patterns that may present at different stages during the course of disease. These include changes believed to be primarily related to the underlying neurodegenerative process of the disease as well as those brought about secondarily, for example, by pharmacologic treatment. Also, sleep disturbances seen in Parkinson's disease can range from temporarily increased daytime sleepiness after introduction of a dopamine agonist to the therapeutic regime to specific sleep-related diagnoses such as restless legs syndrome, rapid eye movement sleep behavior disorder, periodic limb movements in sleep, and sleep-related breathing disorders such as obstructive sleep apnea. In this review, we discuss the different specific sleep disturbances that arise in the context of Parkinson's disease with a special emphasis on epidemiology, pathophysiology, and diagnosis.

A rule-based automatic sleep staging method

In this paper, a rule-based automatic sleep staging method was proposed. Twelve features including temporal and spectrum analyses of the EEG, EOG, and EMG signals were utilized. Normalization was applied to each feature to eliminating individual differences. A hierarchical decision tree with fourteen rules was constructed for sleep stage classification. Finally, a smoothing process considering the temporal contextual information was applied for the continuity. The overall agreement and kappa coefficient of the proposed method applied to the all night polysomnography (PSG) of seventeen healthy subjects compared with the manual scorings by R&K rules can reach 86.68% and 0.79, respectively. This method can integrate with portable PSG system for sleep evaluation at-home in the near future.

Humoral sleep regulation; interleukin-1 and tumor necrosis factor

Two substances, the cytokines interleukin-1 beta (IL1β) and tumor necrosis factor alpha (TNFα), known for their many physiological roles, for example, cognition, synaptic plasticity, and immune function, are also well characterized in their actions of sleep regulation. These substances promote non-rapid eye movement sleep and can induce symptoms associated with sleep loss such as sleepiness, fatigue, and poor cognition. IL1β and TNFα are released from glia in response to extracellular ATP. They bind to their receptors on neurons resulting in neuromodulator and neurotransmitter receptor up/downregulation (e.g., adenosine and glutamate receptors) leading to altered neuronal excitability and function, that is, a state change in the local network. Synchronization of state between local networks leads to emergent whole brain oscillations, such as sleep/wake cycles.

Pattern recognition approaches and computational systems tools for ultra performance liquid chromatography-mass spectrometry-based comprehensive metabolomic profiling and pathways analysis of biological data sets

Metabolomics represents an emerging and powerful discipline that provides an accurate and dynamic picture of the phenotype of biosystems through the study of potential metabolites that could be used for therapeutic targets and discovery of new drugs. Metabolomic network construction has led to the integration of metabolites associated with the caused perturbation of multiple pathways. Herein, we present a method for the construction of efficient networks with regard to that Jujuboside B (JuB) protects against insomnia as a case study. UPLC/ESI-SYNAPT-HDMS coupled with pattern recognition methods including PCA, PLS-DA, OPLS-DA, and computational systems analysis were integrated to obtain comprehensive metabolomic profiling and pathways of the large biological data sets. Among the regulated pathways, twelve biomarkers were identified and tryptophan metabolism, phenylalanine, tyrosine, tryptophan biosynthesis, arachidonic acid metabolism, and phenylalanine metabolism related network were acutely perturbed. Results not only supplied a systematic view of the development and progression of insomnia but also were used to analyze the therapeutic effects of JuB, a widely used anti-insomina medicine in clinics. The results showed that JuB administration could provide satisfactory effects on insomnia through partially regulating the perturbed pathway. We have constructed a metabolomic feature network of JuB to protect against insomnia. The most promising use in the near future would be to clarify pathways for the drugs and get biomarkers for these pathways, to help guide testable predictions, provide insights into drug action mechanisms, and enable us to increase research productivity toward metabolomic drug discovery.

Potential drug targets on insomnia and intervention effects of Jujuboside A through metabolic pathway analysis as revealed by UPLC/ESI-SYNAPT-HDMS coupled with pattern recognition approach

Potential metabolites from the metabolic pathways could be therapeutic targets and useful for the discovery of broad spectrum drugs. UPLC/ESI-SYNAPT-HDMS coupled with pattern recognition methods including PCA, PLS-DA, OPLS-DA and Heatmap were integrated to examine the global metabolic signature of insomnia and intervention effects of Jujuboside A (JuA). Six unique pathways of the insomnia were identified using Ingenuity Pathway Analysis (IPA) software. The VIP-value threshold cutoff of the metabolites was set to 10, above this threshold, were filtered out as potential target biomarkers. Sixteen distinct metabolites were identified from these pathways, and 6 of them can be considered for rational drug design. It was further experimental validation that the changes in metabolic profiling were restored to their baseline values after JuA treatment according to the multivariate data analysis. Potential metabolite network of the insomnia was preliminarily predicted JuA-target interaction networks, and could be further explored for in silico docking studies with suitable drugs. Thus, our method is an efficient procedure for drug target identification through metabolic analysis. It can guide testable predictions, provide insights into drug action mechanisms and enable us to increase research productivity toward metabolomic drug discovery.

Metabolomic study of insomnia and intervention effects of Suanzaoren decoction using ultra-performance liquid-chromatography/electrospray-ionization synapt high-definition mass spectrometry

Metabolomics is the comprehensive assessment of endogenous metabolites of a biological system in a holistic context, and its property consists with the global view of traditional Chinese medicine (TCM). Suanzaoren decoction (SZRD), an ancient TCM formulae, has been used for treating insomnia for centuries, and its mechanism remains unclear completely. This paper was designed to explore globally metabolomic characters of the insomnia and the therapeutic effects of SZRD. Ultra-performance liquid-chromatography/electrospray-ionization synapt high-definition mass spectrometry (UPLC/ESI-SYNAPT-HDMS) combined with pattern recognition approaches including principal component analysis (PCA), partial least squares-discriminant analysis (PLS-DA) and orthogonal projection to latent structures discriminate analysis (OPLS-DA) were integrated to approximate the comprehensive metabolic signature and discover differentiating metabolites. The changes in metabolic profiling were restored to their baseline values after SZRD treatment according to the PCA score plots. Altogether, the current metabonomic approach based on UPLC/ESI-SYNAPT-HDMS indicate 20 ions (9 in the negative mode, 11 in the positive mode) as "differentiating metabolites". The alterations in these metabolites were associated with perturbations in amino acid and fatty acid metabolism, in response to insomnia through immune and nervous system. Of note, we found that SZRD increases sleep activity and exhibits binding affinity for serotonin receptors. These results implicate the therapeutic effects of SZRD may mediate through serotonergic activation. Our findings also show the robust UPLC/ESI-SYNAPT-HDMS techniques is promising for metabolites profiling analysis of TCM and open new perspectives to using metabolomics platform to resolve special TCM issues.

Impaired GABA and glycine transmission triggers cardinal features of rapid eye movement sleep behavior disorder in mice

Rapid eye movement (REM) sleep behavior disorder (RBD) is a neurological disease characterized by loss of normal REM motor inhibition and subsequent dream enactment. RBD is clinically relevant because it predicts neurodegenerative disease onset (e.g., Parkinson's disease) and is clinically problematic because it disrupts sleep and results in patient injuries and hospitalization. Even though the cause of RBD is unknown, multiple lines of evidence indicate that abnormal inhibitory transmission underlies the disorder. Here, we show that transgenic mice with deficient glycine and GABA transmission have a behavioral, motor, and sleep phenotype that recapitulates the cardinal features of RBD. Specifically, we show that mice with impaired glycine and GABA(A) receptor function exhibit REM motor behaviors, non-REM muscle twitches, sleep disruption, and EEG slowing--the defining disease features. Importantly, the RBD phenotype is rescued by drugs (e.g., clonazepam and melatonin) that are routinely used to treat human disease symptoms. Our findings are the first to identify a potential mechanism for RBD--we show that deficits in glycine- and GABA(A)-mediated inhibition trigger the full spectrum of RBD symptoms. We propose that these mice are a useful resource for investigating in vivo disease mechanisms and developing potential therapeutics for RBD.

Dissociated wake-like and sleep-like electro-cortical activity during sleep

Sleep is traditionally considered a global process involving the whole brain. However, recent studies have shown that sleep depth is not evenly distributed within the brain. Sleep disorders, such as sleepwalking, also suggest that EEG features of sleep and wakefulness might be simultaneously present in different cerebral regions. In order to probe the coexistence of dissociated (wake-like and sleep-like) electrophysiological behaviors within the sleeping brain, we analyzed intracerebral electroencephalographic activity drawn from sleep recordings of five patients with pharmacoresistant focal epilepsy without sleep disturbances, who underwent pre-surgical intracerebral electroencephalographic investigation. We applied spectral and wavelet transform analysis techniques to electroencephalographic data recorded from scalp and intracerebral electrodes localized within the Motor cortex (Mc) and the dorso-lateral Prefrontal cortex (dlPFc). The Mc showed frequent Local Activations (lasting from 5 to more than 60s) characterized by an abrupt interruption of the sleep electroencephalographic slow waves pattern and by the appearance of a wake-like electroencephalographic high frequency pattern (alpha and/or beta rhythm). Local activations in the Mc were paralleled by a deepening of sleep in other regions, as expressed by the concomitant increase of slow waves in the dlPFc and scalp electroencephalographic recordings. These results suggest that human sleep can be characterized by the coexistence of wake-like and sleep-like electroencephalographic patterns in different cortical areas, supporting the hypothesis that unusual phenomena, such as NREM parasomnias, could result from an imbalance of these two states.

Local sleep in awake rats

When the brain is awake, neurons in the cerebral cortex fire irregularly and the electroencephalogram (EEG) displays low amplitude, high frequency fluctuations. After falling asleep, neurons start oscillating between ON periods, when they fire as during wake, and OFF periods, when they stop firing altogether, and the EEG displays high amplitude slow waves. But what happens to neuronal firing after a long period of wake? We show here in freely behaving rats that, after prolonged wake, cortical neurons can go briefly “OFF line” as they do in sleep, accompanied by slower waves in the local EEG. Strikingly, neurons often go OFF line in one cortical area and not in another. During these periods of “local sleep”, whose incidence increases with wake duration, rats appear awake, active, and display a wake EEG. However, they are progressively impaired in a sugar pellet reaching task. Thus, though both the EEG and behavior indicate wakefulness, local populations of neurons in the cortex may be falling asleep, with negative consequences on performance.

Regional slow waves and spindles in human sleep

The most prominent EEG events in sleep are slow waves, reflecting a slow (<1 Hz) oscillation between up and down states in cortical neurons. It is unknown whether slow oscillations are synchronous across the majority or the minority of brain regions--are they a global or local phenomenon? To examine this, we recorded simultaneously scalp EEG, intracerebral EEG, and unit firing in multiple brain regions of neurosurgical patients. We find that most sleep slow waves and the underlying active and inactive neuronal states occur locally. Thus, especially in late sleep, some regions can be active while others are silent. We also find that slow waves can propagate, usually from medial prefrontal cortex to the medial temporal lobe and hippocampus. Sleep spindles, the other hallmark of NREM sleep EEG, are likewise predominantly local. Thus, intracerebral communication during sleep is constrained because slow and spindle oscillations often occur out-of-phase in different brain regions.

Sleepwalking, a possible side effect of antipsychotic medication

Two case examples and a review of the sleep literature illustrate the potential of antipsychotic medication to trigger sleepwalking episodes in the context of schizophrenia. Causative hypotheses are briefly reviewed, as well as risk factors, differential diagnosis, and management. Sleepwalking may contribute to delusions, aggression, and accidental suicide. It is important to investigate sleep disorders in schizophrenia. They are not rare and may contribute to behavior that increases the stigma and isolation of individuals with schizophrenia.

Sleep disorders in neurodegenerative diseases

The aim of this review is to provide data on sleep disturbances in three categories of neurodegenerative disorders: synucleinopathies, tauopathies, and other diseases (this heterogeneous group includes also spinocerebellar degeneration and amyotrophic lateral sclerosis). Analysing and knowing sleep disorders in neurodegenerative diseases may offer important insights into the pathomechanism of some of these diseases and calls attention to the still insufficiently known 'sleep neurology'. The identification of sleep disorders in some neurodegenerative conditions may make their diagnosis easier and earlier; for example, rapid eye movements sleep behaviour disorder may precede any other clinical manifestation of synucleinopathies by more than 10 years.

A rule-based automatic sleep staging method

In this paper, a rule-based automatic sleep staging method was proposed. Twelve features, including temporal and spectrum analyses of the EEG, EOG, and EMG signals, were utilized. Normalization was applied to each feature to reduce the effect of individual variability. A hierarchical decision tree, with fourteen rules, was constructed for sleep stage classification. Finally, a smoothing process considering the temporal contextual information was applied for the continuity. The average accuracy and kappa coefficient of the proposed method applied to the all night polysomnography (PSG) of twenty subjects compared with the manual scorings reached 86.5% and 0.78, respectively. This method can assist the clinical staff reduce the time required for sleep scoring in the future.

Beyond dreams: do sleep-related movements contribute to brain development?

Conventional wisdom has long held that the twitches of sleeping infants and adults are by-products of a dreaming brain. With the discovery of active (or REM) sleep in the 1950s and the recognition soon thereafter that active sleep is characterized by inhibition of motor outflow, researchers elaborated on conventional wisdom and concluded that sleep-related twitches are epiphenomena that result from incomplete blockade of dream-related cortical activity. This view persists despite the fact that twitching is unaffected in infants and adults when the cortex is disconnected from the brainstem. In 1966, Roffwarg and colleagues introduced the ontogenetic hypothesis, which addressed the preponderance of active sleep in early infancy. This hypothesis posited that the brainstem mechanisms that produce active sleep provide direct ascending stimulation to the forebrain and descending stimulation to the musculature, thereby promoting brain and neuromuscular development. However, this hypothesis and the subsequent work that tested it did not directly address the developmental significance of twitching or sensory feedback as a contributor to activity-dependent development. Here I review recent findings that have inspired an elaboration of the ontogenetic hypothesis. Specifically, in addition to direct brainstem activation of cortex during active sleep, sensory feedback arising from limb twitches produces discrete and substantial activation of somatosensory cortex and, beyond that, of hippocampus. Delineating how twitching during active sleep contributes to the establishment, refinement, and maintenance of neural circuits may aid our understanding of the early developmental events that make sensorimotor integration possible. In addition, twitches may prove to be sensitive and powerful tools for assessing somatosensory function in humans across the lifespan as well as functional recovery in individuals with injuries or conditions that affect sensorimotor function.

Obstructive sleep apnea alters sleep stage transition dynamics

INTRODUCTION

Enhanced characterization of sleep architecture, compared with routine polysomnographic metrics such as stage percentages and sleep efficiency, may improve the predictive phenotyping of fragmented sleep. One approach involves using stage transition analysis to characterize sleep continuity.

METHODS AND PRINCIPAL FINDINGS

We analyzed hypnograms from Sleep Heart Health Study (SHHS) participants using the following stage designations: wake after sleep onset (WASO), non-rapid eye movement (NREM) sleep, and REM sleep. We show that individual patient hypnograms contain insufficient number of bouts to adequately describe the transition kinetics, necessitating pooling of data. We compared a control group of individuals free of medications, obstructive sleep apnea (OSA), medical co-morbidities, or sleepiness (n = 374) with mild (n = 496) or severe OSA (n = 338). WASO, REM sleep, and NREM sleep bout durations exhibited multi-exponential temporal dynamics. The presence of OSA accelerated the "decay" rate of NREM and REM sleep bouts, resulting in instability manifesting as shorter bouts and increased number of stage transitions. For WASO bouts, previously attributed to a power law process, a multi-exponential decay described the data well. Simulations demonstrated that a multi-exponential process can mimic a power law distribution.

CONCLUSION AND SIGNIFICANCE

OSA alters sleep architecture dynamics by decreasing the temporal stability of NREM and REM sleep bouts. Multi-exponential fitting is superior to routine mono-exponential fitting, and may thus provide improved predictive metrics of sleep continuity. However, because a single night of sleep contains insufficient transitions to characterize these dynamics, extended monitoring of sleep, probably at home, would be necessary for individualized clinical application.

Localized suppression of cortical growth hormone-releasing hormone receptors state-specifically attenuates electroencephalographic delta waves

Growth hormone-releasing hormone (GHRH) promotes non-rapid eye movement sleep (NREMS), in part via a well characterized hypothalamic sleep-promoting site. However, GHRH may also act in the cortex to influence sleep. Application of GHRH to the surface of the cortex changes electroencephalographic (EEG) delta power. GHRH and the GHRH receptor (GHRHR) mRNAs are detectable in the rat cortex, and the expression of cortical GHRHR is activity dependent. Here, we microinjected a GHRH antagonist or GHRHR small interfering RNA (siGHRHR) onto the somatosensory cortex surface in rats. The unilateral application of the GHRH antagonist ipsilaterally decreased EEG delta wave power during NREMS, but not wakefulness, during the initial 40 min after injection. Similarly, the injection of siGHRHR reduced cortical expression of GHRHR and suppressed NREMS EEG delta wave power during 20-24 h after injection. Using the fura-2 calcium imaging technique, cultured cortical cells responded to GHRH by increasing intracellular calcium. Approximately 18% of the GHRH-responsive cells were GABAergic as illustrated by glutamic acid decarboxylase-67 (GAD67) immunostaining. Double labeling for GAD67 and GHRHR in vitro and in vivo indicated that only a minority of cortical GHRHR-containing cells were GABAergic. Our data suggest that endogenous cortical GHRH activates local cortical cells to affect EEG delta wave power state-specifically. Results are also consistent with the hypothesis that GHRH contributes to local network state regulation.

Dreaming and the brain: from phenomenology to neurophysiology

Dreams are a remarkable experiment in psychology and neuroscience, conducted every night in every sleeping person. They show that the human brain, disconnected from the environment, can generate an entire world of conscious experiences by itself. Content analysis and developmental studies have promoted understanding of dream phenomenology. In parallel, brain lesion studies, functional imaging and neurophysiology have advanced current knowledge of the neural basis of dreaming. It is now possible to start integrating these two strands of research to address fundamental questions that dreams pose for cognitive neuroscience: how conscious experiences in sleep relate to underlying brain activity; why the dreamer is largely disconnected from the environment; and whether dreaming is more closely related to mental imagery or to perception.

Impact of generalized brain arousal on sexual behavior

Although there is an extensive amount known about specific sensory and motor functions of the vertebrate brain, less is understood about the regulation of global brain states. We have recently proposed that a function termed generalized arousal (Ag) serves as the most elemental driving force in the nervous system, responsible for the initial activation of all behavioral responses. An animal with increased generalized CNS arousal is characterized by greater motor activity, increased responsivity to sensory stimuli, and greater emotional lability. Implicit in this theory was the prediction that increases in generalized arousal would augment specific motivated behaviors that depend on arousal. Here, we address the idea directly by testing two lines of mice bred for high or low levels of generalized arousal and assessing their responses in tests of specific forms of behavioral arousal, sex and anxiety/exploration. We report that animals selected for differential generalized arousal exhibit marked increases in sensory, motor, and emotional reactivity in our arousal assay. Furthermore, male mice selected for high levels of generalized arousal were excitable and showed more incomplete mounts before the first intromission (IN), but having achieved that IN, they exhibited far fewer IN before ejaculating, as well as ejaculating much sooner after the first IN, thus indicating a high level of sexual arousal. Additionally, high-arousal animals of both sexes exhibited greater levels of anxiety-like behaviors and reduced exploratory behavior in the elevated plus maze and light-dark box tasks. Taken together, these data illustrate the impact of Ag on motivated behaviors.

[Sleep disorders in the elderly]

BACKGROUND

Sleep disorders are common in the elderly, and may lead to substantially impaired quality of life. Many of these disorders are not diagnosed or treated. This article covers treatment options and characteristics of common sleep disorders in the elderly.

MATERIAL AND METHODS

The article is based on the authors' own research and clinical experience, and on articles identified through non-systematic searches in Pubmed.

RESULTS

Many somatic and psychological complaints are associated with sleep disorders; depression is the most common comorbid diagnosis.

INTERPRETATION

A thorough assessment of the patient's sleep pattern is crucial before treatment is instigated. Pharmacological intervention is the most common treatment, but serious side effects are common and there is a high risk of addiction. Effective non-pharmacological interventions are available, also for the elderly.

Sleep deprivation: implications for obstetric practice in the United States

Recent advances in basic science have expanded our understanding of the function of sleep and of the effects of sleep deprivation on human cognitive and psychomotor performance. In addition, a growing volume of data documents potential detrimental effects of sleep deprivation on medical practice. Such data have special implications for a specialty in which sleep deprivation is sometimes the norm. A review of this evidence suggests the pressing need for a reassessment of individual and small group obstetric practice, particularly as it relates to labor and delivery care; the current model of care in which each woman is delivered by the same provider who delivers prenatal care is generally not tenable in a culture increasingly focused on patient safety.

Physiological markers of local sleep

Substantial evidence suggests that brain regions that have been disproportionately used during waking will require a greater intensity and/or duration of subsequent sleep. For example, rats use their whiskers in the dark and their eyes during the light, and this is manifested as a greater magnitude of electroencephalogram (EEG) slow-wave activity in the somatosensory and visual cortex during sleep in the corresponding light and dark periods respectively. The parsimonious interpretation of such findings is that sleep is distributed across local brain regions and is use-dependent. The fundamental properties of sleep can also be experimentally defined locally at the level of small neural assemblies such as cortical columns. In this view, sleep is orchestrated, but not fundamentally driven, by central mechanisms. We explore two physiological markers of local, use-dependent sleep, namely, an electrical marker apparent as a change in the size and shape of an electrical evoked response, and a metabolic marker evident as an evoked change in blood volume and oxygenation delivered to activated tissue. Both markers, applied to cortical columns, provide a means to investigate physiological mechanisms for the distributed homeostatic regulation of sleep, and may yield new insights into the consequences of sleep loss and sleep pathologies on waking brain function.

Evidence of dissociated arousal states during NREM parasomnia from an intracerebral neurophysiological study

STUDY OBJECTIVES

Arousal parasomnias are expressions of sleep/ wake state dissociations in which wakefulness and NREM sleep seem to coexist. We describe the results of a neurophysiological (intracerebral EEG) investigation that captured an episode of confusional arousal.

DESIGN

Observational analysis.

SETTING

Tertiary sleep center.

SUBJECT

A 20-year-old male with refractory focal epilepsy.

MEASUREMENTS AND RESULTS

The intracerebral EEG findings documented the presence of a local arousal of the motor and cingulate cortices associated with increased delta activity in the frontoparietal associative cortices; these findings were noted preceding the onset and persisting throughout the episode.

CONCLUSIONS

The presence of dissociated sleep/wake states in confusional arousals is the expression not of a global phenomenon, but rather of the coexistence of different local states of being: arousal of the motor and cingulate cortices and inhibition of the associative ones. Whether this is an exclusive feature of NREM parasomnias, or a common substrate on which other triggering elements act, needs to be clarified.

The role of cytokines in sleep regulation

Interleukin-1 beta (IL1) and tumor necrosis factor alpha (TNF) promote non-rapid eye movement sleep under physiological and inflammatory conditions. Additional cytokines are also likely involved but evidence is insufficient to conclude that they are sleep regulatory substances. Many of the symptoms induced by sleep loss, e.g. sleepiness, fatigue, poor cognition, enhanced sensitivity to pain, can be elicited by injection of exogenous IL1 or TNF. We propose that ATP, released during neurotransmission, acting via purine P2 receptors on glia releases IL1 and TNF. This mechanism may provide the means by which the brain keeps track of prior usage history. IL1 and TNF in turn act on neurons to change their intrinsic properties and thereby change input-output properties (i.e. state shift) of the local network involved. Direct evidence indicates that cortical columns oscillate between states, one of which shares properties with organism sleep. We conclude that sleep is a local use-dependent process influenced by cytokines and their effector molecules such as nitric oxide, prostaglandins and adenosine.

Parasomnias in childhood

Common childhood parasomnias, including those occurring at sleep onset and during rapid eye movement sleep or non-rapid eye movement sleep and their ontogeny are discussed. The events may be distressing to both the patient and family members. Stereotypic movements characteristic of some parasomnias most likely arise from disinhibition of subcortical central pattern generators. Genetic predisposition, an inherent instability of non-rapid eye movement sleep and underlying sleep disturbances such as obstructive sleep apnea may predispose to the activation of confusional arousals, sleep walking or sleep terrors. Many parasomnias can be recognized by history alone, but some require nocturnal polysomnography for appropriate diagnosis and management. A scheme to distinguish non-rapid eye movement sleep parasomnias from nocturnal seizures is provided. Behavioral therapy has a role in the management of many childhood parasomnias, but evidence based recommendations are as yet unavailable.

Sleep-associated movement disorders and heart failure

Sleep-associated movement disorders are a broad group of sleep disorders characterized by involuntary movements that may disrupt sleep. Relatively little is known about the clinical consequences of sleep-associated movement disorders on cardiovascular health. Because these disorders manifest mostly during sleep, recognizing a movement disorder can be particularly difficult. Nevertheless, patients can have frequent arousals and suffer from similar sleep deprivation, fragmentation, and autonomic disruption as occurs in sleep-disordered breathing. Subsequently, these disorders may have a serious impact on daytime function and perception of health in patients with chronic heart failure.

Parasomnias of childhood

PURPOSE OF REVIEW

To enhance the ability of the practitioner to diagnose and manage children with parasomnias in the office setting.

RECENT FINDINGS

Over 80% of preschool-age children experience parasomnia events. Instability in the regulation of sleep continuity might underlie sleep walking, sleep terrors, and confusional arousals. Catathernia or nocturnal groaning is a parasomnia that is recognized in adults but frequently has onset during childhood.

SUMMARY

Common childhood parasomnias such as hypnic starts, rhythmic movement disorder, sleep paralysis, confusional arousals, sleepwalking, sleep terrors, enuresis, and nightmares are discussed. These events may lead to significant concern and worry for the parents. Most parasomnias are recognizable by history alone, but some may require nocturnal polysomnography for accurate diagnosis and determining an underlying trigger factor. Findings on nocturnal polysomnography are described. Sleep terrors, confusional arousals and sleepwalking may mimic seizures; distinguishing seizures from parasomnias is discussed. There is a genetic predisposition to many childhood parasomnias. Management techniques, including behavioral therapy, are reviewed. Unfortunately, evidence-based recommendations are as yet unavailable. The management of sleep enuresis continues to remain a significant challenge.

Sleep as a fundamental property of neuronal assemblies

Sleep is vital to cognitive performance, productivity, health and well-being. Earlier theories of sleep presumed that it occurred at the level of the whole organism and that it was governed by central control mechanisms. However, evidence now indicates that sleep might be regulated at a more local level in the brain: it seems to be a fundamental property of neuronal networks and is dependent on prior activity in each network. Such local-network sleep might be initiated by metabolically driven changes in the production of sleep-regulatory substances. We discuss a mathematical model which illustrates that the sleep-like states of individual cortical columns can be synchronized through humoral and electrical connections, and that whole-organism sleep occurs as an emergent property of local-network interactions.

Unearthing the phylogenetic roots of sleep

Why we sleep remains one of the enduring unanswered questions in biology. At its core, sleep can be defined behaviorally as a homeostatically regulated state of reduced movement and sensory responsiveness. The cornerstone of sleep studies in terrestrial mammals, including humans, has been the measurement of coordinated changes in brain activity during sleep measured using the electroencephalogram (EEG). Yet among a diverse set of animals, these EEG sleep traits can vary widely and, in some cases, are absent, raising questions as to whether they define a universal, or even essential, feature of sleep. Over the past decade, behaviorally defined sleep-like states have been identified in a series of genetic model organisms, including fish, flies and worms. Genetic analyses in these systems are revealing a remarkable conservation in the underlying mechanisms controlling sleep behavior. Taken together, these studies suggest an ancient origin for sleep and raise the possibility that model organism genetics may reveal the molecular mechanisms that guide sleep and wake.

Ten-year follow-up of mandibular advancement devices for the management of snoring and sleep apnea

STATEMENT OF PROBLEM

Intraoral mandibular advancement devices have become widely used in recent years for the management of snoring and sleep apnea, and short-term effectiveness has been demonstrated. However, there is a shortage of data regarding long-term compliance.

PURPOSE

The purpose of this study was to investigate the long-term compliance of patients who were provided with a mandibular advancement device.

MATERIAL AND METHODS

Records of 180 patients who were provided with a mandibular advancement device in 1996 were available for review. A questionnaire was sent to all of these patients inquiring about continued device usage, comfort, and effectiveness. Questions were also asked about smoking, alcohol consumption, height, and weight. Data were analyzed with chi-square tests for any association between these factors and success of the device (alpha=.05).

RESULTS

The response rate was 40%, with 72 replies. Of this number, 34 patients were currently wearing the device every night, with a further 13 wearing the device for up to 6 nights per week. Thirty-one of the respondents who were wearing the device felt more refreshed on waking. The median body mass index (BMI) was 30, 8 were smokers, and 12 subjects drank more than 20 units of alcohol per week. Few adverse effects of the device were reported.

CONCLUSIONS

The mandibular advancement device appears to be an effective long-term solution for a significant number of patients with problem snoring and also those with mild to moderate obstructive sleep apnea.