Thermoneutral temperature exposure enhances slow-wave sleep with a correlated improvement in amyloid pathology in a triple-transgenic mouse model of Alzheimer's disease.

Accumulation of amyloid-ß (Aß) plays an important role in Alzheimer's disease (AD) pathology. There is growing evidence that disordered sleep may accelerate AD pathology by impeding the physiological clearance of Aß from the brain that occurs in normal sleep. Therapeutic strategies for improving sleep quality may therefore help slow disease progression. It is well documented that the composition and dynamics of sleep are sensitive to ambient temperature. We therefore compared Aß pathology and sleep metrics derived from polysomnography in 12-month-old female 3xTg-AD mice (n = 8) exposed to thermoneutral temperatures during the light period over 4 weeks to those of age- and sex-matched controls (n = 8) that remained at normal housing temperature (22°C) during the same period. The treated group experienced greater proportions of slow wave sleep (SWS)-i.e. epochs of elevated 0.5-2 Hz EEG slow wave activity during non-rapid eye movement (NREM) sleep-compared to controls. Assays performed on mouse brain tissue harvested at the end of the experiment showed that exposure to thermoneutral temperatures significantly reduced levels of DEA-soluble (but not RIPA- or formic acid-soluble) Aß40 and Aß42 in the hippocampus, though not in the cortex. With both groups pooled together and without regard to treatment condition, NREM sleep continuity and any measure of SWS within NREM at the end of the treatment period were inversely correlated with DEA-soluble Aß40 and Aß42 levels, again in the hippocampus but not in the cortex. These findings suggest that experimental manipulation of SWS could offer useful clues into the mechanisms and treatment of AD.

Selective REM sleep restriction in mice using a device designed for tunable somatosensory stimulation.

BACKGROUND: Sleep perturbation is widely used to investigate the physiological mechanisms that mediate sleep-wake dynamics, and to isolate the specific roles of sleep in health and disease. However, state-of-the-art methods to accomplish sleep perturbation in preclinical models are limited in their throughput, flexibility, and specificity. NEW METHOD: A system was developed to deliver vibro-tactile somatosensory stimulation aimed at controlled, selective sleep perturbation. The frequency and intensity of stimulation can be tuned to target a variety of experimental applications, from sudden arousal to sub-threshold transitions between light and deep stages of NREM sleep. This device was activated in closed-loop to selectively interrupt REM sleep in mice. RESULTS: Vibro-tactile stimulation effectively and selectively interrupted REM sleep - significantly reducing the average REM bout duration relative to matched, unstimulated baseline recordings. As REM sleep was repeatedly interrupted, homeostatic mechanisms prompted a progressively quicker return to REM sleep. These effects were dependent on the parameters of stimulation applied. COMPARISON WITH EXISTING METHODS: Existing sleep perturbation systems often require moving parts within the cage and/or restrictive housing. The system presented is unique in that it interrupts sleep without invading the animal's space. The ability to vary stimulation parameters is a great advantage over existing methods, as it allows for adaptation in response to habituation and/or circadian/homeostatic changes in arousal threshold. CONCLUSIONS: The proposed method of stimulation demonstrates feasibility in affecting mouse sleep within a standard home cage environment, thus limiting environmental stress. Furthermore, the ability to tune frequency and intensity of stimulation allows for graded control over the extent of sleep perturbation, which potentially expands the utility of this technology beyond applications related to sleep.

Effects of light therapy on sleep/wakefulness, daily rhythms, and the central orexin system in a diurnal rodent model of seasonal affective disorder.

BACKGROUND: Bright light therapy (BLT) is the first-line treatment for seasonal affective disorder. However, the neural mechanisms underlying BLT are unclear. To begin filling this gap, the present study examined the impact of BLT on sleep/wakefulness, daily rhythms, and the wakefulness-promoting orexin/hypocretin system in a diurnal rodent, Nile grass rats (Arvicanthis niloticus). METHODS: Male and female grass rats were housed under a 12:12 h light/dark cycle with dim light (50 lx) during the day. The experimental group received daily 1-h early morning BLT (full-spectrum white light, 10,000 lx), while the control group received narrowband red light for 4 weeks. Sleep/wakefulness and in-cage locomotor activity were monitored, followed by examination of hypothalamic prepro-orexin and orexin receptors OX1R and OX2R expression in corticolimbic brain regions. RESULTS: The BLT group had higher wakefulness during light treatment, better nighttime sleep quality, and improved daily rhythm entrainment compared to controls. The impact of BLT on the orexin system was sex- and brain region-specific, with males showing higher OX1R and OX2R in the CA1, while females showed higher prepro-orexin but lower OX1R and OX2R in the BLA, compared to same-sex controls. LIMITATIONS: The present study focused on the orexin system in a limited number of brain regions at a single time point. Sex wasn't a statistical factor, as male and female cohorts were run independently. CONCLUSIONS: The diurnal grass rats show similar behavioral responses to BLT as humans, thus could be a good model for further elucidating the neural mechanisms underlying the therapeutic effects of BLT.

Altered synaptic connectivity and brain function in mice lacking microglial adapter protein Iba1.

Growing evidence indicates that microglia impact brain function by regulating synaptic pruning and formation as well as synaptic transmission and plasticity. Iba1 (ionized Ca+2-binding adapter protein 1), encoded by the Allograft inflammatory factor 1 (Aif1) gene, is an actin-interacting protein in microglia. Although Iba1 has long been used as a cellular marker for microglia, its functional role remains unknown. Here, we used global, Iba1-deficient (Aif1-/-) mice to characterize microglial activity, synaptic function, and behavior. Microglial imaging in acute hippocampal slices and fixed tissues from juvenile mice revealed that Aif1-/- microglia display reductions in ATP-induced motility and ramification, respectively. Biochemical assays further demonstrated that Aif1-/- brain tissues exhibit an altered expression of microglial-enriched proteins associated with synaptic pruning. Consistent with these changes, juvenile Aif1-/- mice displayed deficits in the excitatory synapse number and synaptic drive assessed by neuronal labeling and whole-cell patch-clamp recording in acute hippocampal slices. Unexpectedly, microglial synaptic engulfment capacity was diminished in juvenile Aif1-/- mice. During early postnatal development, when synapse formation is a predominant event in the hippocampus, the excitatory synapse number was still reduced in Aif1-/- mice. Together, these findings support an overall role of Iba1 in excitatory synaptic growth in juvenile mice. Lastly, postnatal synaptic deficits persisted in adulthood and correlated with significant behavioral changes in adult Aif1-/- mice, which exhibited impairments in object recognition memory and social interaction. These results suggest that Iba1 critically contributes to microglial activity underlying essential neuroglia developmental processes that may deeply influence behavior.

A real-time sleep scoring framework for closed-loop sleep manipulation in mice.

Subtle changes in sleep architecture can accompany and be symptomatic of many diseases or disorders. In order to probe and understand the complex interactions between sleep and health, the ability to model, track, and modulate sleep in preclinical animal models is vital. While various methods have been described for scoring experimental sleep recordings, few are designed to work in real time - a prerequisite for closed-loop sleep manipulation. In the present study, we have developed algorithms and software to classify sleep in real time and validated it on C57BL/6 mice (n = 8). Hidden Markov models of baseline sleep dynamics were fitted using an unsupervised algorithm to electroencephalogram (EEG) and electromyogram (EMG) data for each mouse, and were able to classify sleep in a manner highly concordant with manual scoring (Cohen's Kappa >75%) up to 3 weeks after model construction. This approach produced reasonably accurate estimates of common sleep metrics (proportion, mean duration, and number of bouts). After construction, the models were used to track sleep in real time and accomplish selective rapid eye movement (REM) sleep restriction by triggering non-invasive somatosensory stimulation. During REM restriction trials, REM bout duration was significantly reduced, and the classifier continued to perform satisfactorily despite the disrupted sleep patterns. The software can easily be tailored for use with other commercial or customised methods of sleep disruption (e.g. stir bar, optogenetic stimulation, etc.) and could serve as a robust platform to facilitate closed-loop experimentation. The source code and documentation are freely available upon request from the authors.

Genetic variation regulates opioid-induced respiratory depression in mice.

In the U.S., opioid prescription for treatment of pain nearly quadrupled from 1999 to 2014. The diversion and misuse of prescription opioids along with increased use of drugs like heroin and fentanyl, has led to an epidemic in addiction and overdose deaths. The most common cause of opioid overdose and death is opioid-induced respiratory depression (OIRD), a life-threatening depression in respiratory rate thought to be caused by stimulation of opioid receptors in the inspiratory-generating regions of the brain. Studies in mice have revealed that variation in opiate lethality is associated with strain differences, suggesting that sensitivity to OIRD is genetically determined. We first tested the hypothesis that genetic variation in inbred strains of mice influences the innate variability in opioid-induced responses in respiratory depression, recovery time and survival time. Using the founders of the advanced, high-diversity mouse population, the Diversity Outbred (DO), we found substantial sex and genetic effects on respiratory sensitivity and opiate lethality. We used DO mice treated with morphine to map quantitative trait loci for respiratory depression, recovery time and survival time. Trait mapping and integrative functional genomic analysis in GeneWeaver has allowed us to implicate Galnt11, an N-acetylgalactosaminyltransferase, as a gene that regulates OIRD.

A comparative study of sleep and diurnal patterns in house mouse (Mus musculus) and Spiny mouse (Acomys cahirinus).

Most published sleep studies use three species: human, house mouse, or Norway rat. The degree to which data from these species captures variability in mammalian sleep remains unclear. To gain insight into mammalian sleep diversity, we examined sleep architecture in the spiny basal murid rodent Acomys cahirinus. First, we used a piezoelectric system validated for Mus musculus to monitor sleep in both species. We also included wild M. musculus to control for alterations generated by laboratory-reared conditions for M. musculus. Using this comparative framework, we found that A. cahirinus, lab M. musculus, and wild M. musculus were primarily nocturnal, but exhibited distinct behavioral patterns. Although the activity of A. cahirinus increased sharply at dark onset, it decreased sharply just two hours later under group and individual housing conditions. To further characterize sleep patterns and sleep-related variables, we set up EEG/EMG and video recordings and found that A. cahirinus sleep significantly more than M. musculus, exhibit nearly three times more REM, and sleep almost exclusively with their eyes open. The observed differences in A. cahirinus sleep architecture raise questions about the evolutionary drivers of sleep behavior.

Recent advances in understanding the genetics of sleep.

Sleep is a ubiquitous and complex behavior in both its manifestation and regulation. Despite its essential role in maintaining optimal performance, health, and well-being, the genetic mechanisms underlying sleep remain poorly understood. Here, we review the forward genetic approaches undertaken in the last four years to elucidate the genes and gene pathways affecting sleep and its regulation. Despite an increasing number of studies and mining large databases, a coherent picture on "sleep" genes has yet to emerge. We highlight the results achieved by using unbiased genetic screens mainly in humans, mice, and fruit flies with an emphasis on normal sleep and make reference to lessons learned from the circadian field.

Chemical sympathectomy reduces peripheral inflammatory responses to acute and chronic sleep fragmentation.

Sleep loss contributes to the development of cardiovascular, metabolic, and neurological disorders by promoting a systemic proinflammatory phenotype. The neuroendocrine-immune mechanisms contributing to such pathologies are poorly understood. The sympathetic nervous system (SNS) regulates immunity and is often activated following sleep disturbances. The aims of this study were to determine 1) the effect of SNS inhibition on inflammatory responses to sleep fragmentation (SF) and 2) whether homeostasis can be restored after 1 wk of recovery sleep. We measured stress responses (norepinephrine and corticosterone), gene expression levels of pro- and anti-inflammatory cytokines in peripheral (heart, liver, and spleen) tissues, and protein levels of cytokines and chemokines in serum of female mice that were subjected to acute SF for 24 h, chronic SF for 8 wk, or 7 days of recovery after chronic SF. In each experiment, SF and control mice were chemically sympathectomized with 6-hydroxydopamine (6-OHDA) or injected with vehicle. Both acute and chronic SF elevated mRNA and protein levels of cytokines in peripheral tissues. Changes in inflammatory responses mirrored stress-axes activation, with increased corticosterone and norepinephrine in SF mice. 6-OHDA treatment significantly alleviated SF-induced inflammation, thus providing evidence of SNS regulation of peripheral inflammation from SF. Effects of chronic SF were more severe than acute SF, and 1 wk of recovery from SF sufficiently alleviated peripheral inflammatory responses but not NE responses.

A Microbe Associated with Sleep Revealed by a Novel Systems Genetic Analysis of the Microbiome in Collaborative Cross Mice.

The microbiome influences health and disease through complex networks of host genetics, genomics, microbes, and environment. Identifying the mechanisms of these interactions has remained challenging. Systems genetics in laboratory mice (Mus musculus) enables data-driven discovery of biological network components and mechanisms of host-microbial interactions underlying disease phenotypes. To examine the interplay among the whole host genome, transcriptome, and microbiome, we mapped QTL and correlated the abundance of cecal messenger RNA, luminal microflora, physiology, and behavior in a highly diverse Collaborative Cross breeding population. One such relationship, regulated by a variant on chromosome 7, was the association of Odoribacter (Bacteroidales) abundance and sleep phenotypes. In a test of this association in the BKS.Cg-Dock7m +/+ Leprdb/J mouse model of obesity and diabetes, known to have abnormal sleep and colonization by Odoribacter, treatment with antibiotics altered sleep in a genotype-dependent fashion. The many other relationships extracted from this study can be used to interrogate other diseases, microbes, and mechanisms.

Active Time-Restricted Feeding Improved Sleep-Wake Cycle in db/db Mice.

People with diabetes are more likely to experience sleep disturbance than those without. Sleep disturbance can cause daytime sleepiness in diabetic patients, which may impair their daytime performance or even lead to workplace injuries. Therefore, restoring the normal sleep-wake cycle is critical for diabetic patients who experience daytime sleepiness. Previous data on a diabetic mouse model, the db/db mice, have demonstrated that the total sleep time and sleep fragmentation are increased and the daily rhythm of the sleep-wake cycle is attenuated. Accumulating evidence has shown that active time-restricted feeding (ATRF), in which the timing of food availability is restricted to the active-phase, is beneficial to metabolic health. However, it is unknown whether ATRF restores the normal sleep-wake cycle in diabetes. To test that, we used a non-invasive piezoelectric system to monitor the sleep-wake profile in the db/db mice with ad libitum feeding (ALF) as a baseline and then followed with ATRF. The results showed that at baseline, db/db mice exhibited abnormal sleep-wake patterns: the sleep time percent during the light-phase was decreased, while during the dark-phase it was increased with unusual cycling compared to control mice. In addition, the sleep bout length during both the light-phase and the full 24-h period was shortened in db/db mice. Analysis of the sleep-wake circadian rhythm showed that ATRF effectively restored the circadian but suppressed the ultradian oscillations of the sleep-wake cycle in the db/db mice. In conclusion, ATRF may serve as a novel strategy for treating diabetes-induced irregularity of the sleep-wake cycle.

The effects of aging on sleep parameters in a healthy, melatonin-competent mouse model.

BACKGROUND: Sleep disturbances are common maladies associated with human age. Sleep duration is decreased, sleep fragmentation is increased, and the timing of sleep onset and sleep offset is earlier. These disturbances have been associated with several neurodegenerative diseases. Mouse models for human sleep disturbances can be powerful due to the accessibility to neuroscientific and genetic approaches, but these are hampered by the fact that most mouse models employed in sleep research have spontaneous mutations in the biosynthetic pathway(s) regulating the rhythmic production of the pineal hormone melatonin, which has been implicated in human sleep. PURPOSE AND METHOD: The present study employed a non-invasive piezoelectric measure of sleep wake cycles in young, middle-aged and old CBA mice, a strain capable of melatonin biosynthesis, to investigate naturally-occurring changes in sleep and circadian parameters as the result of aging. RESULTS: The results indicate that young mice sleep less than do middle-aged or aged mice, especially during the night, while the timing of activity onset and acrophase is delayed in aged mice compared to younger mice. CONCLUSION: These data point to an effect of aging on the quality and timing of sleep in these mice but also that there are fundamental differences between control of sleep in humans and in laboratory mice.

Effects of acute lying and sleep deprivation on the behavior of lactating dairy cows.

The objective was to determine the effects of sleep or lying deprivation on the behavior of dairy cows. Data were collected from 8 multi- and 4 primiparous cows (DIM = 199 ± 44 (mean ± SD); days pregnant = 77 ± 30). Using a crossover design, each cow experienced: 1) sleep deprivation implemented by noise or physical contact when their posture suggested sleep, and 2) lying deprivation imposed by a grid placed on the pen floor. One day before treatment (baseline), and treatment day (treatment) were followed by a 12-d washout period (with the first 7 d used to evaluate recovery). Study days were organized from 2100 to 2059. During habituation (d -3 and -2 before treatment), baseline (d -1), and trt (d 0), housing was individual boxstalls (mattress with no bedding). After treatment, cows returned to sand-bedded freestalls for a 7-d recovery period (d 1 to 7) where data on lying behaviors were collected. Following the recovery period, an additional 5-d period was provided to allow the cows a 12-d period between exposures to treatments. Daily lying time, number lying bouts, bout duration, and number of steps were recorded by dataloggers attached to the hind leg of cows throughout the study period. Data were analyzed using a mixed model including fixed effects of treatment (sleep deprivation vs. sleep and lying deprivation), day, and their interaction with significant main effects separated using a PDIFF statement (P ≤ 0.05). Interactions between treatment and day were detected for daily lying time and the number of bouts. Lying time was lower for both treatments during the treatment period compared to baseline. Lying time increased during the recovery period for both lying and sleep deprived cows. However, it took 4 d for the lying deprived cows to fully recover their lying time after treatment, whereas it took the sleep deprived cows 2 d for their lying time to return to baseline levels. Results suggest that both sleep and lying deprivation can have impact cow behavior. Management factors that limit freestall access likely reduce lying time and sleep, causing negative welfare implications for dairy cows.

Effects of the dual orexin receptor antagonist DORA-22 on sleep in 5XFAD mice.

INTRODUCTION: Sleep disruption is a characteristic of Alzheimer's disease (AD) that may exacerbate disease progression. This study tested whether a dual orexin receptor antagonist (DORA) would enhance sleep and attenuate neuropathology, neuroinflammation, and cognitive deficits in an AD-relevant mouse model, 5XFAD. METHODS: Wild-type (C57Bl6/SJL) and 5XFAD mice received chronic treatment with vehicle or DORA-22. Piezoelectric recordings monitored sleep and spatial memory was assessed via spontaneous Y-maze alternations. Aß plaques, Aß levels, and neuroinflammatory markers were measured by immunohistochemistry, enzyme-linked immunosorbent assay, and real-time polymerase chain reaction, respectively. RESULTS: In 5XFAD mice, DORA-22 significantly increased light-phase sleep without reducing Aß levels, plaque density, or neuroinflammation. Effects of DORA-22 on cognitive deficits could not be determined because the 5XFAD mice did not exhibit deficits. DISCUSSION: These findings suggest that DORAs may improve sleep in AD patients. Further investigations should optimize the dose and duration of DORA-22 treatment and explore additional AD-relevant animal models and cognitive tests.

Novel TNF receptor-1 inhibitors identified as potential therapeutic candidates for traumatic brain injury.

BACKGROUND: Traumatic brain injury (TBI) begins with the application of mechanical force to the head or brain, which initiates systemic and cellular processes that are hallmarks of the disease. The pathological cascade of secondary injury processes, including inflammation, can exacerbate brain injury-induced morbidities and thus represents a plausible target for pharmaceutical therapies. We have pioneered research on post-traumatic sleep, identifying that injury-induced sleep lasting for 6 h in brain-injured mice coincides with increased cortical levels of inflammatory cytokines, including tumor necrosis factor (TNF). Here, we apply post-traumatic sleep as a physiological bio-indicator of inflammation. We hypothesized the efficacy of novel TNF receptor (TNF-R) inhibitors could be screened using post-traumatic sleep and that these novel compounds would improve functional recovery following diffuse TBI in the mouse. METHODS: Three inhibitors of TNF-R activation were synthesized based on the structure of previously reported TNF CIAM inhibitor F002, which lodges into a defined TNFR1 cavity at the TNF-binding interface, and screened for in vitro efficacy of TNF pathway inhibition (IκB phosphorylation). Compounds were screened for in vivo efficacy in modulating post-traumatic sleep. Compounds were then tested for efficacy in improving functional recovery and verification of cellular mechanism. RESULTS: Brain-injured mice treated with Compound 7 (C7) or SGT11 slept significantly less than those treated with vehicle, suggesting a therapeutic potential to target neuroinflammation. SGT11 restored cognitive, sensorimotor, and neurological function. C7 and SGT11 significantly decreased cortical inflammatory cytokines 3 h post-TBI. CONCLUSIONS: Using sleep as a bio-indicator of TNF-R-dependent neuroinflammation, we identified C7 and SGT11 as potential therapeutic candidates for TBI.

Out Like a Light? The Effects of a Diurnal Husbandry Schedule on Mouse Sleep and Behavior.

Sleep disruption in humans, caused by shift work, can be detrimental to physical and behavioral health. Nocturnal laboratory mice may experience a similar disruption caused by human daytime activities, but whether this disruption affects their welfare is unknown. We used 48 mice (CD1, C57BL/6, and BALB/c of both sexes) in a factorial design to test a sleep disruption treatment, in which mice were disturbed by providing routine husbandry at either 1000 or 2200 during a 12:12-h light:dark cycle, with lights on at 0700. All mice were exposed for 1 wk to each disruption treatment, and we used a noninvasive sleep monitoring apparatus to monitor and record sleep. To determine whether providing nesting material ameliorated effects of sleep disruption, we tested 4 amounts of nesting material (3, 6, 9, or 12 g) and continuously recorded sleep in the home cage for 2 wk. C57BL/6 mice, regardless of sex or disruption timing, slept the least overall. There was a strong interaction of sex and type of mouse on sleep across 24 h. Mice slept less during the first day of the daytime disturbance than on day 6. These results suggest that disturbance timing affects sleep patterns in mice but not their overall amount of sleep and that the changes in sleep patterns vary between mouse type and sex. In addition, mice appear to both anticipate and acclimate to human activity during the day. Our welfare checks were possibly too predictable and inconsequential to induce true sleep disruption.

Unsupervised Estimation of Mouse Sleep Scores and Dynamics Using a Graphical Model of Electrophysiological Measurements.

The proportion, number of bouts, and mean bout duration of different vigilance states (Wake, NREM, REM) are useful indices of dynamics in experimental sleep research. These metrics are estimated by first scoring state, sometimes using an algorithm, based on electrophysiological measurements such as the electroencephalogram (EEG) and electromyogram (EMG), and computing their values from the score sequence. Isolated errors in the scores can lead to large discrepancies in the estimated sleep metrics. But most algorithms score sleep by classifying the state from EEG/EMG features independently in each time epoch without considering the dynamics across epochs, which could provide contextual information. The objective here is to improve estimation of sleep metrics by fitting a probabilistic dynamical model to mouse EEG/EMG data and then predicting the metrics from the model parameters. Hidden Markov models (HMMs) with multivariate Gaussian observations and Markov state transitions were fitted to unlabeled 24-h EEG/EMG feature time series from 20 mice to model transitions between the latent vigilance states; a similar model with unbiased transition probabilities served as a reference. Sleep metrics predicted from the HMM parameters did not deviate significantly from manual estimates except for rapid eye movement sleep (REM) ([Formula: see text]; Wilcoxon signed-rank test). Changes in value from Light to Dark conditions correlated well with manually estimated differences (Spearman's rho 0.43-0.84) except for REM. HMMs also scored vigilance state with over 90% accuracy. HMMs of EEG/EMG features can therefore characterize sleep dynamics from EEG/EMG measurements, a prerequisite for characterizing the effects of perturbation in sleep monitoring and control applications.

Noninvasive dissection of mouse sleep using a piezoelectric motion sensor.

BACKGROUND: Changes in autonomic control cause regular breathing during NREM sleep to fluctuate during REM. Piezoelectric cage-floor sensors have been used to successfully discriminate sleep and wake states in mice based on signal features related to respiration and other movements. This study presents a classifier for noninvasively classifying REM and NREM using a piezoelectric sensor. NEW METHOD: Vigilance state was scored manually in 4-s epochs for 24-h EEG/EMG recordings in 20 mice. An unsupervised classifier clustered piezoelectric signal features quantifying movement and respiration into three states: one active; and two inactive with regular and irregular breathing, respectively. These states were hypothesized to correspond to Wake, NREM, and REM, respectively. States predicted by the classifier were compared against manual EEG/EMG scores to test this hypothesis. RESULTS: Using only piezoelectric signal features, an unsupervised classifier distinguished Wake with high (89% sensitivity, 96% specificity) and REM with moderate (73% sensitivity, 75% specificity) accuracy, but NREM with poor sensitivity (51%) and high specificity (96%). The classifier sometimes confused light NREM sleep - characterized by irregular breathing and moderate delta EEG power - with REM. A supervised classifier improved sensitivities to 90, 81, and 67% and all specificities to over 90% for Wake, NREM, and REM, respectively. COMPARISON WITH EXISTING METHODS: Unlike most actigraphic techniques, which only differentiate sleep from wake, the proposed piezoelectric method further dissects sleep based on breathing regularity into states strongly correlated with REM and NREM. CONCLUSIONS: This approach could facilitate large-sample screening for genes influencing different sleep traits, besides drug studies or other manipulations.

Tunable somatosensory stimulation for selective sleep restriction studies in rodents.

Many methods for sleep restriction in rodents have emerged, but most are intrusive, lack fine control, and induce stress. Therefore, a versatile, non-intrusive means of sleep restriction that can alter sleep in a controlled manner could be of great value in sleep research. In previous work, we proposed a novel system for closed-loop somatosensory stimulation based on mechanical vibration and applied it to the task of restricting Rapid Eye Movement (REM) sleep in mice [1]. While this system was effective, it was a crude prototype and did not allow precise control over the amplitude and frequency of stimulation applied to the animal. This paper details the progression of this system from a binary, "all-or-none" version to one that allows dynamic control over perturbation to accomplish graded, state-dependent sleep restriction. Its preliminary use is described in two applications: deep sleep restriction in rats, and REM sleep restriction in mice.