Prostaglandins and sleep. Awaking effect of prostaglandins and sleep pattern of essential fatty acids deficient (EFAD) rats

The experiments were carried out to investigate the effects of prostaglandins (PGs) on the sleep pattern in the cat, and in normal and EFAD rats.The data indicate that the duration of slow wave sleep (SWS) was significantly longer in EFAD rats compared with the normal rats. However, no difference in the REM sleep was observed between the two groups. Intraventricular (i.vc.) administration of PGE₁, PGE₂ and PGF_2α increased wakefulness without a significant alteration of REM sleep.PGE₁ administered i.vc. did not alter the duration of SWS or REM sleep in the chronic cat, but induced ponto-geniculo-occipital (PGO) waves (spikes) which are the phasic phenomenon of REM sleep.The fact that previous administration of 5-hydroxytryptophane abolished the PGE₁-induced PGO spiking, might indicate that this drug triggered the spikes mainly via the functional inhibition of the serotonergic system.     

Yoga Ameliorates Performance Anxiety and Mood Disturbance in Young Professional Musicians

Yoga and meditation can alleviate stress, anxiety, mood disturbance, and musculoskeletal problems, and can enhance cognitive and physical performance. Professional musicians experience high levels of stress, performance anxiety, and debilitating performance-related musculoskeletal disorders (PRMDs). The goal of this controlled study was to evaluate the benefits of yoga and meditation for musicians. Young adult professional musicians who volunteered to participate in a 2-month program of yoga and meditation were randomized to a yoga lifestyle intervention group (n = 15) or to a group practicing yoga and meditation only (n = 15). Additional musicians were recruited to a no-practice control group (n = 15). Both yoga groups attended three Kripalu Yoga or meditation classes each week. The yoga lifestyle group also experienced weekly group practice and discussion sessions as part of their more immersive treatment. All participants completed baseline and end-program self-report questionnaires that evaluated music performance anxiety, mood, PRMDs, perceived stress, and sleep quality; many participants later completed a 1-year followup assessment using the same questionnaires. Both yoga groups showed a trend towards less music performance anxiety and significantly less general anxiety/tension, depression, and anger at end-program relative to controls, but showed no changes in PRMDs, stress, or sleep. Similar results in the two yoga groups, despite psychosocial differences in their interventions, suggest that the yoga and meditation techniques themselves may have mediated the improvements. Our results suggest that yoga and meditation techniques can reduce performance anxiety and mood disturbance in young professional musicians.     

Biphasic effects of pimozide on sleep-wakefulness in dogs

Sleep-wakefulness patterns in dogs were studied using computerized on-line power spectral analysis and off-line automatic stage-classification during control recordings and after oral treatment with three doses of the specific dopamine blocker pimozide. A biphasic effect on sleep-wakefulness patterns was found. At 0.016 mg/kg (the ED₅₀-value for the antagonism of apomorphine-induced vomiting in dogs), pimozide significantly increased the time spent awake, and significantly decreased slow wave sleep and REM sleep. No significant effects were obtained with a four times higher dose of pimozide. At 0.16 mg/kg, pimozide significantly decreased the time spent awake and significantly increased slow wave sleep and REM sleep. The effects appear the opposite of those described for apomorphine and suggest that dopamine plays a role in the physiology of sleep-wakefulness regulation.     

Heart Rate Variability,Flow, Mood and Mental Stress During Yoga Practices in Yoga Practitioners,Non-yoga Practitioners and People with Metabolic Syndrome

Heart Rate Variability (HRV) and respiratory sinus arrhythmia are directly associated with autonomic flexibility, self-regulation and well-being, and inversely associated with physiological stress, psychological stress and pathology. Yoga enhances autonomic activity, mitigates stress and benefits stress-related clinical conditions, yet the relationship between autonomic activity and psychophysiological responses during yoga practices and stressful stimuli has not been widely explored. This experimental study explored the relationship between HRV, mood states and flow experiences in regular yoga practitioners (YP), non-yoga practitioners (NY) and people with metabolic syndrome (MetS), during Mental Arithmetic Stress Test (MAST) and various yoga practices. The study found that the MAST placed a cardio-autonomic burden in all participants with the YP group showing the greatest reactivity and the most rapid recovery, while the MetS group had significantly blunted recovery. The YP group also reported a heightened experience of flow and positive mood states compared to NY and MetS groups as well as having a higher vagal tone during all resting conditions. These results suggest yoga practitioners have a greater homeostatic capacity and autonomic, metabolic and physiological resilience. Further studies are now needed to determine if regular yoga practice may improve autonomic flexibility in non-yoga practitioners and metabolic syndrome patients. Clinical Trial No ‘ACTRN 2614001075673’     

The influence of physical activity and yoga on central arterial stiffness

Purpose

Central arterial stiffness is an accepted risk factor for cardiovascular disease. While aerobic activity is associated with reduced stiffness the influence of practicing yoga is unknown. The aims of this study were to: 1) evaluate arterial stiffness in middle-aged adults who regularly practiced yoga, performed regular exercise, or were inactive, 2) evaluate the reproducibility of arterial stiffness measured in the left and right carotid artery and by pulse wave velocity (PWV).

Methods

Twenty six healthy subjects (male and female, 40–65 yrs old) were tested on two separate days. Carotid artery distensibility (DC) was measured with ultrasound. Physical activity was determined by questionnaire.

Results

Yoga and aerobic subjects had similar physical activity levels. Yoga and aerobic groups were not different in either DC (p = 0.26) or PWV (p = 0.21). The sedentary group had lower DC and higher PWV compared to the aerobic and yoga groups (both, p < 0.001). Stiffness measures were reliable day to day (coefficients of variation ~2.5%) and similar between left and right arteries (CV = 2.2%).

Conclusion

Physical activity was a strong predictor of both measures of arterial stiffness, although other factors such as nutritional status need to be accounted for. An independent effect of practicing yoga could not be detected. Stiffness measures were reproducible and left and right sides were consistent with each other.

     

Evidence for the involvement of alpha-2 adrenoceptors in the sedation but not REM sleep inhibition by clonidine in the rat

Rats with implanted electrodes for recording of EEG and EMG underwent 12-h recordings during the light period starting after i.p. injections of clonidine (0.1 mg/kg) alone or in combination with different alpha-adrenoceptor antagonists. Clonidine increased the proportion of time the rats spent in the drowsy stage of wakefulness which corresponds to behavioural sedation and inhibited both deep slow wave sleep and REM sleep for 6-9 hours. The amount of active wakefulness or light slow wave sleep were unaffected by clonidine. Yohimbine (1 mg/kg) reversed the increase in drowsy wakefulness by clonidine and increased active wakefulness without affecting sleep. Phentolamine (10 mg/kg) was ineffective against clonidine. Phenoxybenzamine (20 mg/kg) accentuated the sedative effect and prolonged the REM sleep inhibiting effect of clonidine. Prazosin (3 mg/kg) prolonged both the drowsy stage inducing and deep slow wave plus REM sleep inhibiting effects of clonidine. These electrophysiological results support the view that the sedative effect of clonidine in the rat is mediated by alpha-2 adrenoceptors, whereas in this species other mechanisms, possibly another population of alpha-2 receptors, may be involved in the clonidine-induced suppression of deep slow wave sleep and REM sleep.     

Differential Associations of Early- and Late-Night Sleep with Functional Brain States Promoting Insight to Abstract Task Regularity

Background

Solving a task with insight has been associated with occipital and right-hemisphere activations. The present study tested the hypothesis if sleep-related alterations in functional activation states modulate the probability of insight into a hidden abstract regularity of a task.

Methodology

State-dependent functional activation was measured by beta and alpha electroencephalographic (EEG) activity and spatial synchronization. Task-dependent functional activation was assessed by slow cortical potentials (SPs). EEG parameters during the performance of the Number Reduction Task (NRT) were compared between before sleep and after sleep sessions. In two different groups, the relevant sleep occurred either in the first or in the second half of the night, dominated by slow wave sleep (SWS) or by rapid eye movement (REM) sleep.

Principal Findings

Changes in EEG parameters only occurred in the early-night group, not in the late-night group and indicated occipital and right-hemisphere functional alterations. These changes were associated with off-line consolidation of implicit task representations and with the amount of SWS but they did not predict subsequent insight. The gain of insight was, however, independently associated with changes of spectral beta and alpha measures only in those subjects from the two sleep groups who would subsequently comprehend the hidden regularity of the task. Insight-related enhancement of right frontal asymmetry after sleep did not depend on sleep stages.

Significance

It is concluded that off-line restructuring of implicit information during sleep is accompanied by alterations of functional activation states after sleep. This mechanism is promoted by SWS but not by REM sleep and may contribute to attaining insight after sleep. Original neurophysiologic evidence is provided for alterations of the functional activation brain states after sleep. These alterations are associated with a decrease in controlled processing within the visual system and with an increase in the functional connectivity of the right hemisphere, and are supported by SWS in the first half of the night.     

Loss of Gnas imprinting differentially affects REM/NREM sleep and cognition in mice

It has been suggested that imprinted genes are important in the regulation of sleep. However, the fundamental question of whether genomic imprinting has a role in sleep has remained elusive up to now. In this work we show that REM and NREM sleep states are differentially modulated by the maternally expressed imprinted gene Gnas. In particular, in mice with loss of imprinting of Gnas, NREM and complex cognitive processes are enhanced while REM and REM-linked behaviors are inhibited. This is the first demonstration that a specific overexpression of an imprinted gene affects sleep states and related complex behavioral traits. Furthermore, in parallel to the Gnas overexpression, we have observed an overexpression of Ucp1 in interscapular brown adipose tissue (BAT) and a significant increase in thermoregulation that may account for the REM/NREM sleep phenotypes. We conclude that there must be significant evolutionary advantages in the monoallelic expression of Gnas for REM sleep and for the consolidation of REM-dependent memories. Conversely, biallelic expression of Gnas reinforces slow wave activity in NREM sleep, and this results in a reduction of uncertainty in temporal decision-making processes.     

Elicited pontogeniculooccipital waves and phasic suppression of diaphragm activity in sleep and wakefulness

Fractionations are 20- to 100-ms pauses indiaphragm activity that occur spontaneously during rapid-eye-movement(REM) sleep, sometimes in association with pontogeniculooccipital (PGO)waves. Auditory stimuli can elicit fractionations or PGOwaves during REM sleep, non-REM (NREM) sleep, and waking; however,their interrelationship has not been investigated. To determine whetherthe two phenomena are produced by a common phasic-event generator inREM sleep, we examined PGO waves and fractionations that were elicitedby auditory stimuli (tones) presented to freely behaving cats across states. Tones elicited PGO waves and two types of fractionations: short-latency fractionation responses (SFRs; 10- to 60-ms latencies) and long-latency fractionation responses (LFRs; 60- to 120-ms latencies). Both a PGO wave and a SFR were elicited in60-70% of trials across states, but each could be elicited alone.The latencies and durations of elicited SFRs were similar acrossstates, but the latencies of elicited PGO waves in REM sleep (mean 62.5 ms) were significantly longer than in waking or NREM sleep. Elicited SFRs consistently occur with shorter latencies than do PGO waves, incontrast to spontaneous fractionations, which have a variable relationship to PGO waves and usually occur 10-40 ms after the onset of the PGO wave. The LFR then, elicited mostfrequently during REM sleep, resembles a spontaneous fractionation inits temporal relationship to the PGO wave and may reflect the bias toward motoneuronal inhibition characterizing REM sleep but not NREMsleep or waking. We conclude that, although PGO waves and SFRs sharesome features, like LFRs they probably are generated by differentneuronal populations. In three cats there was no correlation betweenPGO waves and fractionations, whereas in one cat they were associatedin REM sleep (LFRs and SFRs) and waking (SFRs only). Thus the majorityof evidence argues against the existence of a common phasic-eventgenerator in REM sleep.

     

Diurnal Emotional States Impact the Sleep Course

Background

Diurnal emotional experiences seem to affect several characteristics of sleep architecture. However, this influence remains unclear, especially for positive emotions. In addition, electrodermal activity (EDA), a sympathetic robust indicator of emotional arousal, differs depending on the sleep stage. The present research has a double aim: to identify the specific effects of pre-sleep emotional states on the architecture of the subsequent sleep period; to relate such states to the sympathetic activation during the same sleep period.

Methods

Twelve healthy volunteers (20.1 ± 1.0 yo.) participated in the experiment and each one slept 9 nights at the laboratory, divided into 3 sessions, one per week. Each session was organized over three nights. A reference night, allowing baseline pre-sleep and sleep recordings, preceded an experimental night before which participants watched a negative, neutral, or positive movie. The third and last night was devoted to analyzing the potential recovery or persistence of emotional effects induced before the experimental night. Standard polysomnography and EDA were recorded during all the nights.

Results

Firstly, we found that experimental pre-sleep emotional induction increased the Rapid Eye Movement (REM) sleep rate following both negative and positive movies. While this increase was spread over the whole night for positive induction, it was limited to the second half of the sleep period for negative induction. Secondly, the valence of the pre-sleep movie also impacted the sympathetic activation during Non-REM stage 3 sleep, which increased after negative induction and decreased after positive induction.

Conclusion

Pre-sleep controlled emotional states impacted the subsequent REM sleep rate and modulated the sympathetic activity during the sleep period. The outcomes of this study offer interesting perspectives related to the effect of diurnal emotional influences on sleep regulation and open new avenues for potential practices designed to alleviate sleep disturbances.     

Prostaglandins and sleep. Awaking effect of prostaglandins and sleep pattern of essential fatty acids deficient (EFAD) rats.

The experiments were carried out to investigate the effects of prostaglandins (PGs) on the sleep pattern in the cat, and in normal and EFAD rats. The data indicate that the duration of slow wave sleep (SWS) was significantly longer in EFAD rats compared with the normal rats. However, no difference in the REM sleep was observed between the two groups. Intraventricular (i.vc. )administration of PGE1, PGE2 and PGF2alpha increased wakefulness without a significant alteration of REM sleep. PGE1 administered i.vc. did not alter the duration of SWS or REM sleep in the chronic cat, but induced ponto-geniculo-occipital (PGO) waves (spikes) which are the phasic phenomenon of REM sleep. The fact that previous administration of 5-hydroxytryptophane abolished the PGE1-induced PGO spiking, might indicate that this drug triggered the spikes mainly via the functional inhibition of the serotonergic system.     

A phylogenetic analysis of sleep architecture in mammals: the integration of anatomy, physiology, and ecology

Among mammalian species, the time spent in the two main "architectural" states of sleep--slow-wave sleep (SWS) and rapid-eye-movement (REM) sleep--varies greatly. Previous comparative studies of sleep architecture found that larger mammals, those with bigger brains, and those with higher absolute basal metabolic rates (BMR) tended to engage in less SWS and REM sleep. Species experiencing a greater risk of predation also exhibited less SWS and REM sleep. In all cases, however, these studies lacked a formal phylogenetic and theoretical framework and used mainly correlational analyses. Using independent contrasts and an updated data set, we extended existing approaches with path analysis to examine the integrated influence of anatomy, physiology, and ecology on sleep architecture. Path model structure was determined by nonmutually exclusive hypotheses for the function of sleep. We found that species with higher relative BMRs engage in less SWS, whereas species with larger relative brain masses engage in more REM sleep. REM sleep was the only sleep variable strongly influenced by predation risk; mammals sleeping in riskier environments engage in less REM sleep. Overall, we found support for some hypotheses for the function of sleep, such as facilitating memory consolidation or learning, but not others, such as energy conservation.     

Persistence of sleep-temperature coupling after suprachiasmatic nuclei lesions in rats

The suprachiasmatic nucleus (SCN) regulates the circadian rhythms of body temperature (T(b)) and vigilance states in mammals. We studied rats in which circadian rhythmicity was abolished after SCN lesions (SCNx rats) to investigate the association between the ultradian rhythms of sleep-wake states and brain temperature (T(br)), which are exposed after lesions. Ultradian rhythms of T(br) (mean period: 3.6 h) and sleep were closely associated in SCNx rats. Within each ultradian cycle, nonrapid eye movement (NREM) sleep was initiated 5 +/- 1 min after T(br) peaks, after which temperature continued a slow decline (0.02 +/- 0.006 degrees C/min) until it reached a minimum. Sleep and slow wave activity (SWA), an index of sleep intensity, were associated with declining temperature. Cross-correlation analysis revealed that the rhythm of T(br) preceded that of SWA by 2-10 min. We also investigated the thermoregulatory and sleep-wake responses of SCNx rats and controls to mild ambient cooling (18 degrees C) and warming (30 degrees C) over 24-h periods. SCNx rats and controls responded similarly to changes in ambient temperature. Cooling decreased REM sleep and increased wake. Warming increased T(br), blunted the amplitude of ultradian T(br) rhythms, and increased the number of transitions into NREM sleep. SCNx rats and controls had similar percentages of NREM sleep, REM sleep, and wake, as well as the same average T(b) within each 24-h period. Our results suggest that, in rats, the SCN modulates the timing but not the amount of sleep or the homeostatic control of sleep-wake states or T(b) during deviations in ambient temperature.     

Neuronal Avalanches Differ from Wakefulness to Deep Sleep – Evidence from Intracranial Depth Recordings in Humans

Neuronal activity differs between wakefulness and sleep states. In contrast, an attractor state, called self-organized critical (SOC), was proposed to govern brain dynamics because it allows for optimal information coding. But is the human brain SOC for each vigilance state despite the variations in neuronal dynamics? We characterized neuronal avalanches – spatiotemporal waves of enhanced activity - from dense intracranial depth recordings in humans. We showed that avalanche distributions closely follow a power law – the hallmark feature of SOC - for each vigilance state. However, avalanches clearly differ with vigilance states: slow wave sleep (SWS) shows large avalanches, wakefulness intermediate, and rapid eye movement (REM) sleep small ones. Our SOC model, together with the data, suggested first that the differences are mediated by global but tiny changes in synaptic strength, and second, that the changes with vigilance states reflect small deviations from criticality to the subcritical regime, implying that the human brain does not operate at criticality proper but close to SOC. Independent of criticality, the analysis confirms that SWS shows increased correlations between cortical areas, and reveals that REM sleep shows more fragmented cortical dynamics.     

Effects of the Seasons and of Bright Light Administered at Different Times of Day on Sleep EEG and Mood in Patients with Seasonal Affective Disorder

The study examines objective characteristics of sleep in women (n=31) with and without seasonal affective disorder, winter type, before and after a week of light treatment (at either 0800-1000 h, 1600-1800 h or 1800-2000 h). Subsamples of 13 patients and 7 controls were studied additionally in summer, and, among these patients, 9 were also recorded in spring and fall. Ranking the results from the lowest to the largest degree of deviation of sleep structure in patients from the norm yields the sequence: spring -> summer -> winter after light treatment -> fall -> winter before light treatment. In winter before light treatment the total amounts and percentage of slow wave sleep were significantly lower in responders to light (n=13) compared to both nonresponders (n=8) and controls (n=10), while following light treatment the difference disappeared. The reduced amounts of slow wave sleep in the depressive state predicted higher reduction and low posttreatment scores on psychiatric scales. Light treatment and summer season showed similar effects on patients' sleep: they caused an increase of slow wave sleep and a decline of sleep stage 2. Our data do not suggest that time of light treatment is important to achieve an antidepressant effect. Moreover, phase shifting effects of light treatment and of changing season on sleep EEG were not considerable. At the same time, subjective ratings of arousal demonstrated an advance shift of the arousal rhythm after morning and a delay shift after afternoon LT. We did not find significant changes in total amounts and percentage of REM sleep over time. The data suggest that abnormally increased need for REM sleep results in the hypersomnia and may be considered as a trait marker of winter depression. An abnormal architecture of nonREM sleep appears to be a state marker of those patients who benefit from bright light administered during waking hours.     

Sleep and cortical temperature in the Djungarian hamster under baseline conditions and after sleep deprivation

The Djungarian hamster (Phodopus sungorus) is a markedly photoperiodic rodent which exhibits daily torpor under short photoperiod. Normative data were obtained on vigilance states, electroencephalogram (EEG) power spectra (0.25–25.0 Hz), and cortical temperature (T_CRT) under a 168 h light-dark schedule, in 7 Djungarian hamsters for 2 baseline days, 4 h sleep deprivation (SD) and 20 h recovery.During the baseline days total sleep time amounted to 59% of recording time, 67% in the light period and 43% in the dark period. The 4 h SD induced a small increase in the amount of non-rapid eye movement (NREM) sleep and a marked increase in EEG slow-wave activity (SWA; mean power density 0.75–4.0 Hz) within NREM sleep in the first hours of recovery. T_CRT was lower in the light period than in the dark period. It decreased at transitions from either waking or rapid eye movement (REM) sleep to NREM sleep, and increased at the transition from NREM sleep to waking or REM sleep. After SD, T_CRT was lower in all vigilance states.In conclusion, the sleep-wake pattern, EEG spectrum, and time course of T_CRT in the Djungarian hamster are similar to other nocturnal rodents. Also in the Djungarian hamster the time course of SWA seems to reflect a homeostatically regulated process as was formulated in the two-process model of sleep regulation.Abbreviations EEG electroencephalogram - EMG electromyogram - N NREM sleep - NREM non-rapid eye movement - R REM sleep - REM rapid eye movement - SD sleep deprivation - SWA slow-wave activity - T_CRT cortical temperature - TST total sleep time - VS vigilance state - W waking     

The Temporal Structure of Behaviour and Sleep Homeostasis

The amount and architecture of vigilance states are governed by two distinct processes, which occur at different time scales. The first, a slow one, is related to a wake/sleep dependent homeostatic Process S, which occurs on a time scale of hours, and is reflected in the dynamics of NREM sleep EEG slow-wave activity. The second, a fast one, is manifested in a regular alternation of two sleep states – NREM and REM sleep, which occur, in rodents, on a time scale of ∼5–10 minutes. Neither the mechanisms underlying the time constants of these two processes – the slow one and the fast one, nor their functional significance are understood. Notably, both processes are primarily apparent during sleep, while their potential manifestation during wakefulness is obscured by ongoing behaviour. Here, we find, in mice provided with running wheels, that the two sleep processes become clearly apparent also during waking at the level of behavior and brain activity. Specifically, the slow process was manifested in the total duration of waking periods starting from dark onset, while the fast process was apparent in a regular occurrence of running bouts during the waking periods. The dynamics of both processes were stable within individual animals, but showed large interindividual variability. Importantly, the two processes were not independent: the periodic structure of waking behaviour (fast process) appeared to be a strong predictor of the capacity to sustain continuous wakefulness (slow process). The data indicate that the temporal organization of vigilance states on both the fast and the slow time scales may arise from a common neurophysiologic mechanism.     

Heart rate variability and body temperature during the sleep onset period

Heart rate variability (HRV) and body temperature during the sleep onset period was examined. The core body temperature and electrocardiogram were recorded continuously beginning 1 h before lights out (LO) until the end of the first rapid eye movement sleep (REM) in 14 young healthy subjects. HRV was calculated by the MemCalc method. The time course changes in body temperature and HRV was analyzed before and after sleep onset, and during the following eight consecutive phases: the 60 min before LO, the 30 min before LO, LO, first stage 2 (sleep onset), first slow wave sleep (SWS), stage 2 just before REM, start of REM, and end of REM. A clear decline was observed in the ratio of the low frequency (LF) to high frequency (HF) component of HRV (LF/HF), normalized LF (LF/(LF + HF)), and body temperature prior to sleep onset both in the time course of the sleep onset period and in the consecutive phases. The HF increased prior to sleep onset in the consecutive phases, while no clear increase was observed in the time course of sleep onset period. Changes in LF/(LF + HF) and LF/HF preceded SWS and REM. These results suggest the existence of a strong coupling between the cardiac autonomic nervous system and body temperature at the sleep onset period that may not be circadian effects. Furthermore, LF/(LF + HF) and LF/HF may possibly anticipate sleep and the onset of each sleep stage.

     

Central mechanisms of sleep-wakefulness cycle

Brief anatomical, physiological and neurochemical basics of the regulation of wakefulness, slow wave (NREM) sleep and paradoxical (REM) sleep are regarded as representing by the end of the first decade of the second millennium.