Optogenetic disruption of sleep continuity impairs memory consolidation

Memory consolidation has been proposed as a function of sleep. However, sleep is a complex phenomenon characterized by several features including duration, intensity, and continuity. Sleep continuity is disrupted in different neurological and psychiatric conditions, many of which are accompanied by memory deficits. This finding has raised the question of whether the continuity of sleep is important for memory consolidation. However, current techniques used in sleep research cannot manipulate a single sleep feature while maintaining the others constant. Here, we introduce the use of optogenetics to investigate the role of sleep continuity in memory consolidation. We optogenetically targeted hypocretin/orexin neurons, which play a key role in arousal processes. We used optogenetics to activate these neurons at different intervals in behaving mice and were able to fragment sleep without affecting its overall amount or intensity. Fragmenting sleep after the learning phase of the novel object recognition (NOR) task significantly decreased the performance of mice on the subsequent day, but memory was unaffected if the average duration of sleep episodes was maintained at 62-73% of normal. These findings demonstrate the use of optogenetic activation of arousal-related nuclei as a way to systematically manipulate a specific feature of sleep. We conclude that regardless of the total amount of sleep or sleep intensity, a minimal unit of uninterrupted sleep is crucial for memory consolidation.     

快速眼动睡眠期的阻塞型呼吸暂停与高血压

快速眼动(REM)睡眠期阻塞型睡眠呼吸暂停(OSA)是指发生在REM期的阻塞型睡眠呼吸暂停综合征,由于REM期交感神经活性异常增高,因此发生在此期的OSA可以使交感神经活性更高,心血管功能更不稳定。目前认为REM-OSA很可能是OSA相关高血压发生的主要原因,并且也可能是目前OSA相关高血压用持续正压通气(CPAP)治疗效果不明显的重要原因。临床工作中应重视对REM-OSA的诊断和治疗,这对OSA相关高血压的防治具有重要意义。     

Optogenetic activation of septal cholinergic neurons suppresses sharp wave ripples and enhances theta oscillations in the hippocampus

Theta oscillations in the limbic system depend on the integrity of the medial septum. The different populations of medial septal neurons (cholinergic and GABAergic) are assumed to affect different aspects of theta oscillations. Using optogenetic stimulation of cholinergic neurons in ChAT-Cre mice, we investigated their effects on hippocampal local field potentials in both anesthetized and behaving mice. Cholinergic stimulation completely blocked sharp wave ripples and strongly suppressed the power of both slow oscillations (0.5–2 Hz in anesthetized, 0.5–4 Hz in behaving animals) and supratheta (6–10 Hz in anesthetized, 10–25 Hz in behaving animals) bands. The same stimulation robustly increased both the power and coherence of theta oscillations (2–6 Hz) in urethane-anesthetized mice. In behaving mice, cholinergic stimulation was less effective in the theta (4–10 Hz) band yet it also increased the ratio of theta/slow oscillation and theta coherence. The effects on gamma oscillations largely mirrored those of theta. These findings show that medial septal cholinergic activation can both enhance theta rhythm and suppress peri-theta frequency bands, allowing theta oscillations to dominate.Subcortical neuromodulators play a critical role in shifting states of the brain (1, 2). State changes can occur both during sleep and in the waking animal and are instrumental in affecting local circuit computation that supports various functions, including attention, learning, memory, and action (3–5). The septo-hippocampal cholinergic system has been hypothesized to play a critical role in setting network states in the limbic system (4, 6). ACh can affect both short- and long-term plasticity of synaptic connections and provide favorable conditions for encoding information (7–9). These plastic states are associated with hippocampal theta oscillations (10). High theta states are characterized by increased release of ACh that varies in a task-dependent manner on the time scale of seconds (11–13). In contrast, reduced cholinergic activity allows effective spread of excitation in the recurrent CA3 network, giving rise to synchronous sharp wave ripples (SPW-R) (14–16).Inactivation of the medial septum (MS)/diagonal band of Broca abolishes theta oscillations in the hippocampus and entorhinal cortex (17) and results in severe learning deficit (18, 19). Similarly, selective toxin lesion of septal cholinergic neurons produces a several-fold decrease of theta power but not its frequency (20). The phase of the local field potentials (LFP) theta oscillations shifts from the septal to the temporal pole and in the CA3–CA1 axis by ∼180° (21, 22). Thus, at each point in time neurons residing at different locations of the three-dimensional structure of the hippocampus spike at different theta phases yet are bound together by the global theta signal. These numerous sources of theta generators are believed to be coordinated by the reciprocal connections between the septum and hippocampus (23), but the nature of this spatial–temporal coordination is not well understood (24). Both cholinergic and GABAergic neurons, and a small fraction of VGlut2 immunoreactive neurons (25), are believed to play a critical role in such global coordination (26, 27). Although GABAergic neurons of the MS were demonstrated to be entrained at theta frequency, identified cholinergic neurons did not show theta-related discharge pattern (28, 29). Additionally, both GABAergic and cholinergic neurons are affected by the feedback long-range hippocampo-septal inhibitory connections (30).Early studies, performed in anesthetized animals, already suggested a critical role for the cholinergic septo-hippocampal projection in the generation of theta oscillations (6). Indeed, the low-frequency theta present under urethane anesthesia can be fully abolished by antimuscarinic drugs (31). In contrast, atropine or scopolamine fail to abolish theta oscillations during waking exploration (31, 32), although they affect the theta waveform and its amplitude-phase depth profile in the hippocampus (33). Although these previous works are compatible with the hypothesis that the role of septal cholinergic projections is mainly permissive and affects theta power without modulating its frequency (20, 26, 28), direct evidence is missing. The role of septal cholinergic neurons on gamma oscillation and SPW-R is even less understood (14). To address these issues, we used optogenetic activation of septal cholinergic input and examined its impact on hippocampal theta, peri-theta bands, gamma, and ripple oscillations in both anesthetized and freely moving mice.     

Brief Report: Regularly occurring bouts of retinal movements suggest an REM sleep–like state in jumping spiders

Sleep and sleep-like states are present across the animal kingdom, with recent studies convincingly demonstrating sleep-like states in arthropods, nematodes, and even cnidarians. However, the existence of different sleep phases across taxa is as yet unclear. In particular, the study of rapid eye movement (REM) sleep is still largely centered on terrestrial vertebrates, particularly mammals and birds. The most salient indicator of REM sleep is the movement of eyes during this phase. Movable eyes, however, have evolved only in a limited number of lineages—an adaptation notably absent in insects and most terrestrial arthropods—restricting cross-species comparisons. Jumping spiders, however, possess movable retinal tubes to redirect gaze, and in newly emerged spiderlings, these movements can be directly observed through their temporarily translucent exoskeleton. Here, we report evidence for an REM sleep–like state in a terrestrial invertebrate: periodic bouts of retinal movements coupled with limb twitching and stereotyped leg curling behaviors during nocturnal resting in a jumping spider. Observed retinal movement bouts were consistent, including regular durations and intervals, with both increasing over the course of the night. That these characteristic REM sleep–like behaviors exist in a highly visual, long-diverged lineage further challenges our understanding of this sleep state. Comparisons across such long-diverged lineages likely hold important questions and answers about the visual brain as well as the origin, evolution, and function of REM sleep.     

Phenotypes of patients with mild to moderate obstructive sleep apnoea as confirmed by cluster analysis

Background and objective: Patients with OSA manifest different patterns of disease. However, this heterogeneity is more evident in patients with mild‐moderate OSA than in those with severe disease and a high total AHI. We hypothesized that mild‐moderate OSA can be categorized into discreet disease phenotypes, and the aim of this study was to comprehensively describe the pattern of OSA phenotypes through the use of cluster analysis techniques. Methods: The data for 1184 consecutive patients, collected over 24 months, was analysed. Patients with a total AHI of 5–30/h were categorized according to the sleep stage and position in which they were predominantly affected. This categorization was compared with one in which patients were grouped using a K‐means clustering technique with log linear modelling and cross‐tabulation. Results: Patients with mild‐moderate OSA can be categorized according to polysomnographic parameters. This clinical categorization was validated by comparison with a categorization in which patients were grouped by unsupervised K‐means cluster analysis. The clinical groups identified were: (i) rapid eye movement (REM) predominant OSA, 44.6%; (ii) non‐REM predominant OSA, 18.9%; (iii) supine predominant OSA, 61.9%; and (iv) intermittent OSA, 12.4%. Patients categorized as having both REM and supine predominant OSA showed characteristics of both the REM predominant and supine predominant OSA groups. Conclusions: Patients with mild‐moderate OSA show different polysomnographic phenotypes. This approach to categorization more appropriately reflects disease heterogeneity and the likely multiple pathophysiological processes involved in OSA.     

Optogenetic activation of GnRH neurons reveals minimal requirements for pulsatile luteinizing hormone secretion

The mechanisms responsible for generating the pulsatile release of gonadotropins from the pituitary gland are unknown. We develop here a methodology in mice for controlling the activity of the gonadotropin-releasing hormone (GnRH) neurons in vivo to establish the minimal parameters of activation required to evoke a pulse of luteinizing hormone (LH) secretion. Injections of Cre-dependent channelrhodopsin (ChR2)-bearing adeno-associated virus into the median eminence of adult GnRH-Cre mice resulted in the selective expression of ChR2 in hypophysiotropic GnRH neurons. Acute brain slice experiments demonstrated that ChR2-expressing GnRH neurons could be driven to fire with high spike fidelity with blue-light stimulation frequencies up to 40 Hz for periods of seconds and up to 10 Hz for minutes. Anesthetized, ovariectomized mice had optical fibers implanted in the vicinity of GnRH neurons within the rostral preoptic area. Optogenetic activation of GnRH neurons for 30-s to 5-min time periods over a range of different frequencies revealed that 10 Hz stimulation for 2 min was the minimum required to generate a pulse-like increment of LH. The same result was found for optical activation of GnRH projections in the median eminence. Increases in LH secretion were compared with endogenous LH pulse parameters measured from ovariectomized mice. Driving GnRH neurons to exhibit simultaneous burst firing was ineffective at altering LH secretion. These observations provide an insight into how GnRH neurons generate pulsatile LH secretion in vivo.Reproductive functioning in all mammals is critically dependent upon pulsatile gonadotropin secretion (1). Experiments undertaken in the 1980s clearly established that pulsatile luteinizing hormone (LH) and follicle-stimulating hormone secretion were generated by the episodic release of gonadotropin-releasing hormone (GnRH) into the pituitary portal vasculature (2–6). However, a quarter of a century since those experiments were performed, the components and mechanisms responsible for this episodic release of GnRH remain unknown and represent one of the most important unanswered questions in reproductive biology (7).Key parameters such as the number of GnRH neurons involved in a pulse and their patterns of electrical firing are unknown. An important insight into the dynamics of a GnRH pulse has come from fast portal blood sampling in ovariectomized sheep where each GnRH pulse is reported to approximate a square wave beginning sharply over 2 min, remaining elevated for ∼5 min, and then falling to baseline over the next 3 min (8). This allowed speculation that a subgroup of GnRH neurons may fire coordinately for a period of 2–7 min to generate a pulse of GnRH (7). Disappointingly, however, direct electrical recordings of adult GnRH neurons in acute brain slices in vitro have provided no clear correlate of pulsatile hormone secretion (7, 9). Recent investigations into GnRH neuron firing in vivo in anesthetized GnRH-green fluorescent protein (GFP) mice have similarly been unable to shed light on the pulse-generating properties of these cells (10). The most promising insights into the nature of GnRH pulsatility have come from studies of embryonic GnRH neurons in vitro where episodes of burst firing, represented by calcium transients, are found to synchronize occasionally in subpopulations of GnRH neurons in a time frame similar to that of pulsatile GnRH/LH secretion (11, 12).The best way of determining the patterns of GnRH neuron firing that generate an LH pulse would be to record the activity of hypophysiotropic GnRH neurons while simultaneously measuring LH secretion in vivo. At present this remains impossible. An alternative approach that might shed light on this issue would be to determine the minimal patterns of GnRH neuron firing that are capable of generating an LH pulse in vivo. This is now possible using optogenetic approaches, and we report here a strategy that allows hypophysiotropic GnRH neurons to be transfected with channelrhodopsins (ChR2) and subsequently activated in vivo to generate pulses of LH secretion. This reveals that GnRH neurons need only be activated at either their cell bodies or distal projections within the median eminence (ME) for 2 min at a constant 10-Hz firing rate to generate an LH pulse. Surprisingly, synchronizing burst firing among GnRH neurons is ineffective.     

The utility of a 5th nap in multiple sleep latency test

Background

This is the first study that aimed to look specifically at the utility of the 5^th nap in the multiple sleep latency test (MSLT), a test used to assist in the diagnosis of narcolepsy.

Methods

Data was retrospectively collected from the Sleep Disorders Centre of a Tertiary Hospital on patients that had a 5^th nap during their MSLT from the 08^th November 2011 to 12^th November 2014.

Results

Fifty-three patients had a 5^th nap performed out of 378 MSLT studies. In 16% of cases a diagnosis of narcolepsy was given directly due to the inclusion of the 5^th nap on the MSLT. Here a 5^th nap allowed diagnostic criteria of mean sleep latency <8 minutes and >2 SOREMPS to be met. In 53% of cases the mean sleep latency increased due to 5^th nap inclusion; the mean sleep latency of the first four naps was 5.6 vs. 6.7 after inclusion of the 5^th nap.

Conclusions

The 5^th nap is not often performed within the MSLT studies. Our study shows that only a few patients may benefit from a 5^th nap opportunity which also led to increase of the mean sleep latency at the expense of extra time, cost, labour and increased patient anxiety.     

Cortical cholinergic signaling controls the detection of cues

The cortical cholinergic input system has been described as a neuromodulator system that influences broadly defined behavioral and brain states. The discovery of phasic, trial-based increases in extracellular choline (transients), resulting from the hydrolysis of newly released acetylcholine (ACh), in the cortex of animals reporting the presence of cues suggests that ACh may have a more specialized role in cognitive processes. Here we expressed channelrhodopsin or halorhodopsin in basal forebrain cholinergic neurons of mice with optic fibers directed into this region and prefrontal cortex. Cholinergic transients, evoked in accordance with photostimulation parameters determined in vivo, were generated in mice performing a task necessitating the reporting of cue and noncue events. Generating cholinergic transients in conjunction with cues enhanced cue detection rates. Moreover, generating transients in noncued trials, where cholinergic transients normally are not observed, increased the number of invalid claims for cues. Enhancing hits and generating false alarms both scaled with stimulation intensity. Suppression of endogenous cholinergic activity during cued trials reduced hit rates. Cholinergic transients may be essential for synchronizing cortical neuronal output driven by salient cues and executing cue-guided responses.Virtually all cortical regions and layers receive inputs from cholinergic neurons originating in the nucleus basalis of Meynert, the substantia innominata, and the diagonal band of the basal forebrain (BF). Reflecting the seemingly diffuse organization of this projection system, functional conceptualizations traditionally have described acetylcholine (ACh) as a neuromodulator that influences broadly defined behavioral and cognitive processes such as wakefulness, arousal, and gating of input processing (1, 2). However, anatomical studies have revealed a topographic organization of BF cholinergic cell bodies with highly segregated cortical projection patterns (3–7). Such an anatomical organization favors hypotheses describing the cholinergic mediation of discrete cognitive-behavioral processes. Studies assessing the behavioral effects of cholinergic lesions, recording from or stimulating BF neurons in behaving animals have supported such hypotheses, proposing that cholinergic activity enhances sensory coding and mediates the ability of reward-predicting stimuli to control behavior (8–17).In separate experiments using two different tasks, we reported the presence of phasic cholinergic release events (transients) in the medial prefrontal cortex (mPFC) of rodents trained to report the presence of cues (18, 19). These studies used choline-sensitive microelectrodes to measure changes in extracellular choline concentrations that reflect the hydrolysis of newly released ACh by endogenous acetylcholinesterase (SI Results and Discussion). Importantly, such cholinergic transients were not observed in trials in which cues were missed and in which the absence of a cue was correctly reported and rewarded. Cholinergic transients have thus been hypothesized to mediate the detection of cues, specifically defined as the cognitive process that generates a behavioral response by which subjects report the presence of a cue (20).Here we used optogenetic methods to test the causal role of cortical cholinergic transients in cue detection (as defined above). We used a task that consisted of cued and noncued trials and rewarded correct responses for both trial types (hits and correct rejections). Incorrect responses (misses and false alarms, respectively) were not rewarded. We hypothesized that hit rates would be enhanced by generating transients in conjunction with cues, and that hit rates will be reduced by silencing cue-associated endogenous cholinergic signaling. We further reasoned that if cholinergic transients are a mediator of the cue detection response, generating such transients on noncued trials could force invalid detections (false alarms).Phasic cholinergic activity was generated or silenced, in separate sessions, by photoactivation directed toward the cholinergic cell bodies of the BF or the cholinergic terminals locally in the right mPFC. The decision to target right mPFC was based on findings indicating that performance of the task used here enhances cholinergic function in the right, but not left, mPFC in mice (21) and activates right prefrontal regions in humans (19, 22). The present results support the hypothesis that the ability of cues to guide behavior is mediated by phasic cholinergic signaling. Particularly strong support for this hypothesis was obtained by the demonstration that, in the absence of cues, and thus of endogenous transients, photostimulation of either cholinergic soma in the BF or cholinergic terminals in the mPFC increased the number of invalid reports of cues (or false alarms).     

Rapid eye movement and slow-wave sleep rebound after one night of continuous positive airway pressure for obstructive sleep apnoea

Background and objective: Rebound of slow‐wave sleep (SWS) and rapid eye movement (REM) sleep is observed in patients who are on continuous positive airway pressure (CPAP) therapy for obstructive sleep apnoea (OSA); but, neither have been objectively defined. The pressure titration study often represents the first recovery sleep period for patients with OSA. Our aim was to objectively define and identify predictors of SWS and REM sleep rebound following CPAP titration. Methods: Paired diagnostic polysomnography and pressure titration studies from 335 patients were reviewed. Results: The mean apnoea‐hypopnoea index was 40.7 ± 26.1, and minimum oxygen saturation was 76 ± 14.4%. Comparing eight incremental thresholds, a rebound of 20% in REM sleep and a 40% increase in SWS allowed the best separation of prediction models. A 20% rebound in REM sleep was predicted by REM sleep %, non‐REM arousal index (ArI) and total sleep time during diagnostic polysomnography, and male gender (R² = 35.3%). A 40% rebound in SWS was predicted by SWS %, total ArI and REM sleep % during diagnostic polysomnography, and body mass index (R² = 45.4%). Conclusions: A 40% rebound in SWS, but only a 20% rebound in REM sleep on the pressure titration study, is predicted by abnormal sleep architecture and sleep fragmentation prior to the commencement of treatment.     

高血压患者血脂水平与快速动眼型及非快速动眼型阻塞性睡眠呼吸暂停低通气综合征的相关性

[目的]通过回顾性分析高血压合并和未合并阻塞性睡眠呼吸暂停低通气综合征(OSAHS)患者的相关资料,探讨血脂水平与快速动眼型(REM)及非快速动眼型(non-REM)OSAHS的关系。[方法]回顾性分析2017年1月1日—2020年12月31日于北京安贞医院高血压科住院且入院前半年未服用降脂药物的患者478例。收集患者入院时的一般资料(性别、年龄、身高、体质量),检测总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白胆固醇(LDLC)和高密度脂蛋白胆固醇(HDLC),记录氧减指数、最低血氧饱和度和平均血氧饱和度、睡眠呼吸暂停低通气指数(AHI)、24 h收缩压(24h SBP)和24 h舒张压(24h DBP);根据高血压患者是否合并OSAHS分为未合并OSAHS组和合并OSAHS组,对比两组临床资料,采用多因素线性回归方程分析OSAHS的相关影响因素;采用Spearman方程分析血脂水平与OSAHS各项指标的相关性;另根据OSAHS不同分型,分析REM OSAHS和non-REM OSAHS患者AHI与血脂指标的相关性。[结果]多因素线性回归分析显示,体质指数(BMI)、TG是OSAH...     

REM睡眠剥夺对大鼠内脏感觉影响的研究

目的研究快动眼（rapid eye movement，REM）睡眠剥夺对大鼠内脏感觉功能的影响。方法将24只Sprague-Dawley大鼠随机分为正常对照组（home—eagecontml，HC组）、实验对照组（cage—yokedeontrol，YC组）和REM睡眠剥夺组（sleep deprivation，SD组）。采用花瓶技术对SD组进行REM睡眠剥夺。在REM睡眠剥夺的第12h、24h、48h、72h行结直肠扩张（CRD），观察大鼠的腹壁回撤反射（AWR）以测定内脏感觉功能。结果在REM睡眠剥夺的第12、24h，大鼠对80mmHg扩张刺激的AWR评分明显低于YC及HC组；而REM睡眠剥夺的第48、72h，40mmHg、60mmHg、80mmHg扩张刺激的AWR评分明显低于YC及HC组。在REM睡眠剥夺的第48、72h大鼠的初始感觉阈值及疼痛感觉阈值升高。结论REM睡眠剥夺降低大鼠的内脏感觉功能，且与睡眠剥夺时间相关。     

Prospective Study of Nocturnal Desaturation in Patients Receiving Home Oxygen Therapy

Objective Nocturnal desaturation is common in patients with chronic respiratory disease and often worsens the prognosis. Therefore, it should be diagnosed accurately and appropriately treated. The aim of this study was to clarify the diversity of nocturnal desaturation. Methods We prospectively enrolled 58 outpatients diagnosed with chronic respiratory disease receiving home oxygen therapy and measured nocturnal SpO₂ using a portable oximeter. We classified nocturnal desaturation (3% decrease in SpO₂ from baseline) into three patterns: periodic pattern (desaturation duration of <655 seconds), sustained pattern (desaturation duration of ≥655 seconds), and intermittent pattern (desaturation and recovery of SpO₂ repeated with a cycle of several minutes). Results Nocturnal hypoxemia (SpO₂ ≤88% for more than 5 minutes) was found in 23.8% of patients. The percentage of patients with chronic obstructive pulmonary disease (COPD) was significantly higher in the nocturnal hypoxemia group than in the non-hypoxemia group (80% vs. 40.6%, p=0.03). Desaturation with a periodic pattern was found in 81% of patients, desaturation with a sustained pattern was found in 40.5% of patients, and desaturation with an intermittent pattern was found in 59.5% of patients. In patients with COPD, desaturation with a periodic pattern was found in 85.7%, desaturation with a sustained pattern was found in 47.6%, and desaturation with an intermittent pattern was found in 57.1%. Conclusion The SpO₂ waveform of nocturnal hypoxemia was able to be classified into three patterns. Suitable treatment for each pattern might improve the prognosis of these patients.     

Modification of sleep architecture in an animal model of experimental cirrhosis

AIM: To analyze the polygraphic sleep patterns during cirrhosis progression in a rat model by repeated CCl_4 administration.METHODS: Male Wistar rats received three weekly injections of CCl_4 for 11 wk, and were analyzed before and during the induction of cirrhosis. Rats were implanted with electrodes to record their sleep patterns.Polygraph recordings were made weekly over 11 wk for 8 h, during the light period. After a basal recording,rats received three weekly injections of CCl_4. Histological confirmation of cirrhosis was performed after 11 wk.RESULTS: The results showed a progressive decrease in total wake time that reached statistical significance from the second week of treatment. In addition, there was an increase in total time of slow wave sleep (SWS) Ⅱ and rapid eye movement sleep (REM sleep) in most of the 11 wk. SWS Ⅰ showed no significant variations.During the final weeks, a significant increase in REM sleep frequency was also observed. Histological analyses of the livers showed unequivocal signs of cirrhosis.CONCLUSION: These data suggest that hepatic failure produced by CCl_4 administration is capable of modifying the sleep pattern even after only a few doses.     

快速眼动睡眠剥夺后大鼠皮质及海马神经元突触相关蛋白神经颗粒素表达的变化

目的:探讨不同时间的快速眼动(REM)睡眠剥夺对大鼠皮质及海马各区神经颗粒素分子表达变化的影响及意义。方法:Sprague-Dawley大鼠70只,随机分为睡眠剥夺组(SD)、实验环境对照组(TC)和空白对照组(CC)。其中SD组又分为12h、1d、3d、5d、7d共5个时点组。采用改良多平台(MMPM)睡眠剥夺法进行REM睡眠剥夺,运用免疫荧光染色共聚焦显微镜观察REM睡眠剥夺后不同时点大鼠皮质及海马各区的神经颗粒素表达的分布规律和时空变化;同时结合蛋白印迹(Western blot)技术对皮质及全海马神经颗粒素蛋白作选择性半定量分析。结果:神经颗粒素主要分布于正常大脑皮质Ⅱ、Ⅲ层的神经元胞体和树突、海马CA1～CA3锥体细胞层和齿状回颗粒细胞层内。REM睡眠剥夺12h后大鼠皮质神经颗粒素的表达即开始减少,与对照组比较有显著性差异,直至第7d均呈下降趋势;海马结构中神经颗粒素表达未见显著变化。蛋白印迹实验印证了这一结果。结论:REM睡眠剥夺能引起大鼠大脑皮质神经颗粒素表达减少,且随睡眠剥夺时间的延长而渐趋明显,这可能是REM睡眠剥夺引起大脑神经元突触可塑性改变,进而影响大鼠学习记忆功能损害的机制之一。     

快动眼睡眠剥夺对丁酸钠诱导的内脏感觉过敏大鼠模型的调节作用

目的研究丁酸钠灌肠对大鼠内脏感觉功能的影响以及快动眼睡眠剥夺对大鼠内脏感觉功能的调节作用。方法大鼠行丁酸钠溶液灌肠（200mmol／L，6次），对照组行生理盐水灌肠。两组大鼠均在第1次灌肠后的第3、6、9、12、15、18天行结直肠气蠼扩张（CRD），观察大鼠的腹壁回撤反射（AWR）测定内脏感觉功能。丁酸钠灌肠大鼠分为快动眼睡眠剥夺组和对照组。在快动眼睡眠剥夺的第24h、48h、72h行CRD，观察大鼠的腹壁回撤反射（AWR）测定内脏感觉功能。结果第3，6、9、12天，在20、40、60、80mmHg的扩张压力下，丁酸钠灌肠组的AWR评分明显高于生理盐水灌肠组（P＜0．05）。而在第15、18天，丁酸钠灌肠组的AWR评分与对照组无显著性差异（P＞0．05）。快动眼睡眠剥夺的第24h，大鼠对80mmHg扩张刺激的AWR评分明显低于对照组（P＜0．05）；而快动眼睡眠剥夺的第48、72h，大鼠对不同程度扩张刺激的AWR评分均明显低于对照组（P＜0．05）。在快动眼睡眠剥夺的第48、72h大鼠的疼痛感觉阈值升高（P＜0．01）。结论丁酸钠溶液反复灌肠可诱导大鼠内脏感觉过敏；快动眼睡眠剥夺可提高模型鼠的内脏疼痛感觉阈值，降低内脏感觉敏感性。     

Prevalence of concomitant sleep disorders in patients with obstructive sleep apnea

We determined the prevalence of concomitant sleep disorders in patients with a primary diagnosis of obstructive sleep apnea (OSA). We retrospectively analyzed 643 patients, aged 18, with a primary diagnosis of OSA, evaluated by sleep specialists, in whom clinical and polysomnographic data were derived using standardized techniques by reviewing data from a standardized database and clinical charts. Concomitant sleep disorders were listed according to the International Classification of Sleep Disorders (American Academy of Sleep Medicine, 2000). The mean age was 48.5±13.5 years and 55% were male. Racial distributions were African–Americans 51.8% and Caucasian 47%. Indices of disordered breathing were respiratory disturbance index 32.4±30.4/h sleep and time <90% O₂ saturation 44.5±81.6 min. Thirty-one percent of patients had a concomitant sleep disorder. The most common were inadequate sleep hygiene (14.5%) and periodic limb movement disorder (PLMD, 8.1%). Of patients with other sleep disorders, 66.8% had treatment initiated for these disorders. Predictors of inadequate sleep hygiene (logistic regression) were: age (each decade OR=0.678, P=0.000000), gender (for M, OR=0.536), and the presence of at least one other major system disorder (OR=2.123, P=0.0015). Predictors of PLMD were: age (each decade OR=0.794, P=0.0005), gender (for M, OR=0.433, P=0.004), and total sleep time (for each 10 min, OR=0.972, P=0.0013). We conclude that approximately one third of patients with sleep apnea have another identifiable sleep disorder, usually requiring treatment. This suggests that practitioners evaluating and treating sleep apnea ought to be prepared to deal with other sleep disorders as well.     

From the Cover: Optogenetic and pharmacological suppression of spatial clusters of face neurons reveal their causal role in face gender discrimination

Neurons that respond more to images of faces over nonface objects were identified in the inferior temporal (IT) cortex of primates three decades ago. Although it is hypothesized that perceptual discrimination between faces depends on the neural activity of IT subregions enriched with “face neurons,” such a causal link has not been directly established. Here, using optogenetic and pharmacological methods, we reversibly suppressed the neural activity in small subregions of IT cortex of macaque monkeys performing a facial gender-discrimination task. Each type of intervention independently demonstrated that suppression of IT subregions enriched in face neurons induced a contralateral deficit in face gender-discrimination behavior. The same neural suppression of other IT subregions produced no detectable change in behavior. These results establish a causal link between the neural activity in IT face neuron subregions and face gender-discrimination behavior. Also, the demonstration that brief neural suppression of specific spatial subregions of IT induces behavioral effects opens the door for applying the technical advantages of optogenetics to a systematic attack on the causal relationship between IT cortex and high-level visual perception.Face neurons in the inferior temporal (IT) cortex are classically defined as all neurons whose responses discriminate visual images of faces from images of nonface objects (1). By the spirit of this definition, an ideal “face neuron” would be a unit that responds to any image containing a face and does not respond to any image containing only nonface objects. Such a hypothetical face neuron could, in principle, directly support face-detection behavior (detecting images of faces with various poses, sizes, positions, and identities among other stimuli) but is not necessarily useful for other face-related behaviors such as face discrimination (distinguishing two different faces). Thus, the mechanistic relationship between “face (detector) neurons” and other face-related behaviors remains far from clear.Although previous human neuropsychology (2–4), transcranial magnetic stimulation (TMS) (5, 6), and electrophysiological (7, 8) work motivates the hypothesis that face (detector) neurons are causally involved in face discrimination, there is little direct evidence for it. In this study, we aimed to test this hypothesis for one face-discrimination task: Is face gender^* discrimination impaired by temporary silencing of IT subregions enriched with face (detector) neurons? Because distributed IT cortical populations show the computational capacity to support a wide range of invariant object discriminations (9, 10)^†, the main alternative hypothesis we considered is that discrimination of different faces (i.e., different objects) can be causally supported by IT neurons outside of the face-detector neural clusters. Beyond this specific scientific question, our study was also motivated by the larger goal of developing better tools for direct manipulation of high-level visual neural activity in primates. That is, although “correlational” analysis of patterns of neural activity can strongly infer a role for those neurons in supporting a behavior, the most direct way to test the “causal” role of the spiking activity of a subset of neurons in a given behavioral task is to directly perturb that neuronal activity and measure its effect on the behavior (11, 12).Previously, direct electrical perturbation of specific IT subregions had been used to show the causal role of face-detector neurons in face-detection behavior (12), a result that is consistent with the current operational definition of those neurons. Although anecdotal studies in humans reported perceptual distortion of faces after electrical stimulation of large parts of fusiform cortex in humans (13–15), and TMS studies revealed the impact of large-scale perturbation of functional MRI (fMRI)-defined face-selective cortical regions (16) in face recognition (5, 17), a direct causal link between spiking of IT face neurons and face-discrimination behavior has not been established.In this study, using standard electrophysiology techniques in macaque monkeys and the traditional operational definition of face (detector) neurons, we recorded extensively from central IT cortex (CIT) (18) to locate the largest known spatial cluster of face neurons (also known as middle face patch) (ref. 19; see SI Methods for more details). Then, using optogenetic tools, we directly suppressed the spiking activity of ∼1-mm (Fig. S1) subregions of IT cortex enriched with face-detector neurons as well as other nearby IT subregions and assessed the causal contribution of each subregion in face gender-discrimination behavior.In a separate set of experiments, using pharmacological intervention (muscimol microinjection), we aimed to replicate our main optogenetic findings. Although the lower spatial resolution and much lower temporal resolution of pharmacological tools does not allow fine comparison of small IT subregions (as is possible with optogenetics), its bigger spatial impact (∼3-mm diameter) was used to confirm the basic characteristics of our main finding with a well-established neural suppression method.