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Sample records for slow wave sleep

  1. Source modeling sleep slow waves

    PubMed Central

    Murphy, Michael; Riedner, Brady A.; Huber, Reto; Massimini, Marcello; Ferrarelli, Fabio; Tononi, Giulio

    2009-01-01

    Slow waves are the most prominent electroencephalographic (EEG) feature of sleep. These waves arise from the synchronization of slow oscillations in the membrane potentials of millions of neurons. Scalp-level studies have indicated that slow waves are not instantaneous events, but rather they travel across the brain. Previous studies of EEG slow waves were limited by the poor spatial resolution of EEGs and by the difficulty of relating scalp potentials to the activity of the underlying cortex. Here we use high-density EEG (hd-EEG) source modeling to show that individual spontaneous slow waves have distinct cortical origins, propagate uniquely across the cortex, and involve unique subsets of cortical structures. However, when the waves are examined en masse, we find that there are diffuse hot spots of slow wave origins centered on the lateral sulci. Furthermore, slow wave propagation along the anterior−posterior axis of the brain is largely mediated by a cingulate highway. As a group, slow waves are associated with large currents in the medial frontal gyrus, the middle frontal gyrus, the inferior frontal gyrus, the anterior cingulate, the precuneus, and the posterior cingulate. These areas overlap with the major connectional backbone of the cortex and with many parts of the default network. PMID:19164756

  2. Slow Wave Sleep and Long Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Whitmire, Alexandra; Orr, Martin; Arias, Diana; Rueger, Melanie; Johnston, Smith; Leveton, Lauren

    2012-01-01

    While ground research has clearly shown that preserving adequate quantities of sleep is essential for optimal health and performance, changes in the progression, order and /or duration of specific stages of sleep is also associated with deleterious outcomes. As seen in Figure 1, in healthy individuals, REM and Non-REM sleep alternate cyclically, with stages of Non-REM sleep structured chronologically. In the early parts of the night, for instance, Non-REM stages 3 and 4 (Slow Wave Sleep, or SWS) last longer while REM sleep spans shorter; as night progresses, the length of SWS is reduced as REM sleep lengthens. This process allows for SWS to establish precedence , with increases in SWS seen when recovering from sleep deprivation. SWS is indeed regarded as the most restorative portion of sleep. During SWS, physiological activities such as hormone secretion, muscle recovery, and immune responses are underway, while neurological processes required for long term learning and memory consolidation, also occur. The structure and duration of specific sleep stages may vary independent of total sleep duration, and changes in the structure and duration have been shown to be associated with deleterious outcomes. Individuals with narcolepsy enter sleep through REM as opposed to stage 1 of NREM. Disrupting slow wave sleep for several consecutive nights without reducing total sleep duration or sleep efficiency is associated with decreased pain threshold, increased discomfort, fatigue, and the inflammatory flare response in skin. Depression has been shown to be associated with a reduction of slow wave sleep and increased REM sleep. Given research that shows deleterious outcomes are associated with changes in sleep structure, it is essential to characterize and mitigate not only total sleep duration, but also changes in sleep stages.

  3. Slow Wave Sleep and Long Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Orr, M.; Whitmire, A.; Arias, D.; Leveton, L.

    2011-01-01

    To review the literature on slow wave sleep (SWS) in long duration space flight, and place this within the context of the broader literature on SWS particularly with respect to analogous environments such as the Antarctic. Explore how SWS could be measured within the International Space Station (ISS) context with the aim to utilize the ISS as an analog for future extra-orbital long duration missions. Discuss the potential use of emergent minimally intrusive wireless technologies like ZEO for integrated prelaunch, flight, and return to Earth analysis and optimization of SWS (and general quality of sleep).

  4. Human Gamma Oscillations during Slow Wave Sleep

    PubMed Central

    Valderrama, Mario; Crépon, Benoît; Botella-Soler, Vicente; Martinerie, Jacques; Hasboun, Dominique; Alvarado-Rojas, Catalina; Baulac, Michel; Adam, Claude; Navarro, Vincent; Le Van Quyen, Michel

    2012-01-01

    Neocortical local field potentials have shown that gamma oscillations occur spontaneously during slow-wave sleep (SWS). At the macroscopic EEG level in the human brain, no evidences were reported so far. In this study, by using simultaneous scalp and intracranial EEG recordings in 20 epileptic subjects, we examined gamma oscillations in cerebral cortex during SWS. We report that gamma oscillations in low (30–50 Hz) and high (60–120 Hz) frequency bands recurrently emerged in all investigated regions and their amplitudes coincided with specific phases of the cortical slow wave. In most of the cases, multiple oscillatory bursts in different frequency bands from 30 to 120 Hz were correlated with positive peaks of scalp slow waves (“IN-phase” pattern), confirming previous animal findings. In addition, we report another gamma pattern that appears preferentially during the negative phase of the slow wave (“ANTI-phase” pattern). This new pattern presented dominant peaks in the high gamma range and was preferentially expressed in the temporal cortex. Finally, we found that the spatial coherence between cortical sites exhibiting gamma activities was local and fell off quickly when computed between distant sites. Overall, these results provide the first human evidences that gamma oscillations can be observed in macroscopic EEG recordings during sleep. They support the concept that these high-frequency activities might be associated with phasic increases of neural activity during slow oscillations. Such patterned activity in the sleeping brain could play a role in off-line processing of cortical networks. PMID:22496749

  5. Enhancement of sleep slow waves: underlying mechanisms and practical consequences

    PubMed Central

    Bellesi, Michele; Riedner, Brady A.; Garcia-Molina, Gary N.; Cirelli, Chiara; Tononi, Giulio

    2014-01-01

    Even modest sleep restriction, especially the loss of sleep slow wave activity (SWA), is invariably associated with slower electroencephalogram (EEG) activity during wake, the occurrence of local sleep in an otherwise awake brain, and impaired performance due to cognitive and memory deficits. Recent studies not only confirm the beneficial role of sleep in memory consolidation, but also point to a specific role for sleep slow waves. Thus, the implementation of methods to enhance sleep slow waves without unwanted arousals or lightening of sleep could have significant practical implications. Here we first review the evidence that it is possible to enhance sleep slow waves in humans using transcranial direct-current stimulation (tDCS) and transcranial magnetic stimulation. Since these methods are currently impractical and their safety is questionable, especially for chronic long-term exposure, we then discuss novel data suggesting that it is possible to enhance slow waves using sensory stimuli. We consider the physiology of the K-complex (KC), a peripheral evoked slow wave, and show that, among different sensory modalities, acoustic stimulation is the most effective in increasing the magnitude of slow waves, likely through the activation of non-lemniscal ascending pathways to the thalamo-cortical system. In addition, we discuss how intensity and frequency of the acoustic stimuli, as well as exact timing and pattern of stimulation, affect sleep enhancement. Finally, we discuss automated algorithms that read the EEG and, in real-time, adjust the stimulation parameters in a closed-loop manner to obtain an increase in sleep slow waves and avoid undesirable arousals. In conclusion, while discussing the mechanisms that underlie the generation of sleep slow waves, we review the converging evidence showing that acoustic stimulation is safe and represents an ideal tool for slow wave sleep (SWS) enhancement. PMID:25389394

  6. Regional Slow Waves and Spindles in Human Sleep

    PubMed Central

    Nir, Yuval; Staba, Richard J.; Andrillon, Thomas; Vyazovskiy, Vladyslav V.; Cirelli, Chiara; Fried, Itzhak; Tononi, Giulio

    2011-01-01

    SUMMARY The most prominent EEG events in sleep are slow waves, reflecting a slow (<1 Hz) oscillation between up and down states in cortical neurons. It is unknown whether slow oscillations are synchronous across the majority or the minority of brain regions—are they a global or local phenomenon? To examine this, we recorded simultaneously scalp EEG, intracerebral EEG, and unit firing in multiple brain regions of neurosurgical patients. We find that most sleep slow waves and the underlying active and inactive neuronal states occur locally. Thus, especially in late sleep, some regions can be active while others are silent. We also find that slow waves can propagate, usually from medial prefrontal cortex to the medial temporal lobe and hippocampus. Sleep spindles, the other hallmark of NREM sleep EEG, are likewise predominantly local. Thus, intracerebral communication during sleep is constrained because slow and spindle oscillations often occur out-of-phase in different brain regions. PMID:21482364

  7. Slow waves, sharp waves, ripples, and REM in sleeping dragons.

    PubMed

    Shein-Idelson, Mark; Ondracek, Janie M; Liaw, Hua-Peng; Reiter, Sam; Laurent, Gilles

    2016-04-29

    Sleep has been described in animals ranging from worms to humans. Yet the electrophysiological characteristics of brain sleep, such as slow-wave (SW) and rapid eye movement (REM) activities, are thought to be restricted to mammals and birds. Recording from the brain of a lizard, the Australian dragon Pogona vitticeps, we identified SW and REM sleep patterns, thus pushing back the probable evolution of these dynamics at least to the emergence of amniotes. The SW and REM sleep patterns that we observed in lizards oscillated continuously for 6 to 10 hours with a period of ~80 seconds. The networks controlling SW-REM antagonism in amniotes may thus originate from a common, ancient oscillator circuit. Lizard SW dynamics closely resemble those observed in rodent hippocampal CA1, yet they originate from a brain area, the dorsal ventricular ridge, that has no obvious hodological similarity with the mammalian hippocampus. PMID:27126045

  8. Aging and sleep in Williams syndrome: accelerated sleep deterioration and decelerated slow wave sleep decrement.

    PubMed

    Bódizs, Róbert; Gombos, Ferenc; Gerván, Patrícia; Szőcs, Katalin; Réthelyi, János M; Kovács, Ilona

    2014-12-01

    Specific developmental and aging trajectories characterize sleep electroencephalogram (EEG) of typically developing (TD) subjects. Williams syndrome (WS) is marked by sleep alterations and accelerated aging of several anatomo-functional and cognitive measures. Here we test the hypothesis of a premature aging of sleep in WS. Age-related changes of home recorded sleep EEG of 42 subjects (21 WS, 21 age- and gender matched TD subjects, age: 6-29 years) were tested by Pearson correlations and homogeneity-of-slopes analysis. Typical developmental/aging effects of sleep EEGs were observed in TD subjects. Accelerated aging in WS was confirmed by overall sleep/wake measures. Specifically, premature aging was evident in accelerated age-dependent declines in WS subjects' sleep efficiency, as well as in steeper age-related rises in wakefulness and wake after sleep onset (WASO) of the WS group. In contrast, NREM sleep-related measures indicated atypical decelerations of the developmental trends of WS subjects, characterized by the slowing down of the age-related slow wave sleep (SWS) declines mirrored by the lack of age-dependent increase in Stage 2 (S2) sleep. Age-effects in sleep EEG power spectra were not different among the groups. Objectively measured sleep disruption of subjects with WS is age-dependent and increasing with age. Moreover, these data suggest atypical pre- and postpubertal neural development in WS, with sleep/wake balance and REM sleep time indicating accelerated aging while NREM sleep composition revealing signs of an as yet unidentified, perhaps compensatory developmental delay. PMID:25178705

  9. Circadian regulation of slow waves in human sleep: Topographical aspects

    PubMed Central

    Lazar, Alpar S.; Lazar, Zsolt I.; Dijk, Derk-Jan

    2015-01-01

    Slow waves (SWs, 0.5–4 Hz) in field potentials during sleep reflect synchronized alternations between bursts of action potentials and periods of membrane hyperpolarization of cortical neurons. SWs decline during sleep and this is thought to be related to a reduction of synaptic strength in cortical networks and to be central to sleep's role in maintaining brain function. A central assumption in current concepts of sleep function is that SWs during sleep, and associated recovery processes, are independent of circadian rhythmicity. We tested this hypothesis by quantifying all SWs from 12 EEG derivations in 34 participants in whom 231 sleep periods were scheduled across the circadian cycle in a 10-day forced-desynchrony protocol which allowed estimation of the separate circadian and sleep-dependent modulation of SWs. Circadian rhythmicity significantly modulated the incidence, amplitude, frequency and the slope of the SWs such that the peaks of the circadian rhythms in these slow-wave parameters were located during the biological day. Topographical analyses demonstrated that the sleep-dependent modulation of SW characteristics was most prominent in frontal brain areas whereas the circadian effect was similar to or greater than the sleep-dependent modulation over the central and posterior brain regions. The data demonstrate that circadian rhythmicity directly modulates characteristics of SWs thought to be related to synaptic plasticity and that this modulation depends on topography. These findings have implications for the understanding of local sleep regulation and conditions such as ageing, depression, and neurodegeneration which are associated with changes in SWs, neural plasticity and circadian rhythmicity. PMID:25979664

  10. Circadian regulation of slow waves in human sleep: Topographical aspects.

    PubMed

    Lazar, Alpar S; Lazar, Zsolt I; Dijk, Derk-Jan

    2015-08-01

    Slow waves (SWs, 0.5-4Hz) in field potentials during sleep reflect synchronized alternations between bursts of action potentials and periods of membrane hyperpolarization of cortical neurons. SWs decline during sleep and this is thought to be related to a reduction of synaptic strength in cortical networks and to be central to sleep's role in maintaining brain function. A central assumption in current concepts of sleep function is that SWs during sleep, and associated recovery processes, are independent of circadian rhythmicity. We tested this hypothesis by quantifying all SWs from 12 EEG derivations in 34 participants in whom 231 sleep periods were scheduled across the circadian cycle in a 10-day forced-desynchrony protocol which allowed estimation of the separate circadian and sleep-dependent modulation of SWs. Circadian rhythmicity significantly modulated the incidence, amplitude, frequency and the slope of the SWs such that the peaks of the circadian rhythms in these slow-wave parameters were located during the biological day. Topographical analyses demonstrated that the sleep-dependent modulation of SW characteristics was most prominent in frontal brain areas whereas the circadian effect was similar to or greater than the sleep-dependent modulation over the central and posterior brain regions. The data demonstrate that circadian rhythmicity directly modulates characteristics of SWs thought to be related to synaptic plasticity and that this modulation depends on topography. These findings have implications for the understanding of local sleep regulation and conditions such as ageing, depression, and neurodegeneration which are associated with changes in SWs, neural plasticity and circadian rhythmicity. PMID:25979664

  11. Enhancing Slow Wave Sleep with Sodium Oxybate Reduces the Behavioral and Physiological Impact of Sleep Loss

    PubMed Central

    Walsh, James K.; Hall-Porter, Janine M.; Griffin, Kara S.; Dodson, Ehren R.; Forst, Elizabeth H.; Curry, Denise T.; Eisenstein, Rhody D.; Schweitzer, Paula K.

    2010-01-01

    Study Objectives: To investigate whether enhancement of slow wave sleep (SWS) with sodium oxybate reduces the impact of sleep deprivation. Design: Double-blind, parallel group, placebo-controlled design Setting: Sleep research laboratory Participants: Fifty-eight healthy adults (28 placebo, 30 sodium oxybate), ages 18-50 years. Interventions: A 5-day protocol included 2 screening/baseline nights and days, 2 sleep deprivation nights, each followed by a 3-h daytime (08:00-11:00) sleep opportunity and a recovery night. Sodium oxybate or placebo was administered prior to each daytime sleep period. Multiple sleep latency test (MSLT), psychomotor vigilance test (PVT), Karolinska Sleepiness Scale (KSS), and Profile of Mood States were administered during waking hours. Measurements and Results: During daytime sleep, the sodium oxybate group had more SWS, more EEG spectral power in the 1-9 Hz range, and less REM. Mean MSLT latency was longer for the sodium oxybate group on the night following the first daytime sleep period and on the day following the second day sleep period. Median PVT reaction time was faster in the sodium oxybate group following the second day sleep period. The change from baseline in SWS was positively correlated with the change in MSLT and KSS. During recovery sleep the sodium oxybate group had less TST, SWS, REM, and slow wave activity (SWA) than the placebo group. Conclusions: Pharmacological enhancement of SWS with sodium oxybate resulted in a reduced response to sleep loss on measures of alertness and attention. In addition, SWS enhancement during sleep restriction appears to result in a reduced homeostatic response to sleep loss. Citation: Walsh JK; Hall-Porter JM; Griffin KS; Dodson ER; Forst EH; Curry DT; Eisenstein RD; Schweitzer PK. Enhancing slow wave sleep with sodium oxybate reduces the behavioral and physiological impact of sleep loss. SLEEP 2010;33(9):1217-1225. PMID:20857869

  12. Spontaneous K-Complex Density in Slow-Wave Sleep

    PubMed Central

    Zannat, Wassilatul; Pandi-Perumal, Seithikurippu R.; BaHammam, Ahmed S.; Hussain, M. Ejaz

    2016-01-01

    Purpose To study spontaneous K-complex (KC) densities during slow-wave sleep. The secondary objective was to estimate intra-non-rapid eye movement (NREM) sleep differences in KC density. Materials and Methods It is a retrospective study using EEG data included in polysomnographic records from the archive at the sleep research laboratory of the Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, India. The EEG records of 4459 minutes were used. The study presents a manual identification investigation of KCs in 17 healthy young adult male volunteers (age = 23.82±3.40 years and BMI = 23.42±4.18 kg/m2). Results N3 had a higher KC density than N2 (Z = -2.485, p = 0.013) for all of the probes taken together. Four EEG probes had a higher probe-specific KC density during N3. The inter-probe KC density differed significantly during N2 (χ2 = 67.91, p < .001), N3 (χ2 = 70.62, p < .001) and NREM (χ2 = 68.50, p < .001). The percent distribution of KC decreased uniformly with sleep cycles. Conclusion The inter-probe differences during N3 establish the fronto-central dominance of the KC density regardless of sleep stage. This finding supports one local theory of KC generation. The significantly higher KC density during N3 may imply that the neuro-anatomical origin of slow-wave activity and KC is the same. This temporal alignment with slow-wave activity supports the sleep-promoting function of the KC. PMID:26963714

  13. Acetazolamide for electrical status epilepticus in slow-wave sleep.

    PubMed

    Fine, Anthony L; Wirrell, Elaine C; Wong-Kisiel, Lily C; Nickels, Katherine C

    2015-09-01

    Electrical status epilepticus in slow-wave sleep (ESES) is characterized by nearly continuous spike-wave discharges during non-rapid eye movement (REM) sleep. ESES is present in Landau-Kleffner syndrome (LKS) and continuous spike and wave in slow-wave sleep (CSWS). Sulthiame has demonstrated reduction in spike-wave index (SWI) in ESES, but is not available in the United States. Acetazolamide (AZM) is readily available and has similar pharmacologic properties. Our aims were to assess the effect of AZM on SWI and clinical response in children with LKS and CSWS. Children with LKS or CSWS treated with AZM at our institution were identified retrospectively. Pre- and posttherapy electroencephalography (EEG) studies were evaluated for SWI. Parental and teacher report of clinical improvement was recorded. Six children met criteria for inclusion. Three children (50%) demonstrated complete resolution or SWI <5% after AZM. All children had improvement in clinical seizures and subjective improvement in communication skills and school performance. Five of six children had subjective improvement in hyperactivity and attention. AZM is a potentially effective therapy for children with LKS and CSWS. This study lends to the knowledge of potential therapies that can be used for these disorders, which can be challenging for families and providers. PMID:26230617

  14. Properties of slow oscillation during slow-wave sleep and anesthesia in cats.

    PubMed

    Chauvette, Sylvain; Crochet, Sylvain; Volgushev, Maxim; Timofeev, Igor

    2011-10-19

    Deep anesthesia is commonly used as a model of slow-wave sleep (SWS). Ketamine-xylazine anesthesia reproduces the main features of sleep slow oscillation: slow, large-amplitude waves in field potential, which are generated by the alternation of hyperpolarized and depolarized states of cortical neurons. However, direct quantitative comparison of field potential and membrane potential fluctuations during natural sleep and anesthesia is lacking, so it remains unclear how well the properties of sleep slow oscillation are reproduced by the ketamine-xylazine anesthesia model. Here, we used field potential and intracellular recordings in different cortical areas in the cat to directly compare properties of slow oscillation during natural sleep and ketamine-xylazine anesthesia. During SWS cortical activity showed higher power in the slow/delta (0.1-4 Hz) and spindle (8-14 Hz) frequency range, whereas under anesthesia the power in the gamma band (30-100 Hz) was higher. During anesthesia, slow waves were more rhythmic and more synchronous across the cortex. Intracellular recordings revealed that silent states were longer and the amplitude of membrane potential around transition between active and silent states was bigger under anesthesia. Slow waves were mostly uniform across cortical areas under anesthesia, but in SWS, they were most pronounced in associative and visual areas but smaller and less regular in somatosensory and motor cortices. We conclude that, although the main features of the slow oscillation in sleep and anesthesia appear similar, multiple cellular and network features are differently expressed during natural SWS compared with ketamine-xylazine anesthesia. PMID:22016533

  15. Sleep slow-wave activity regulates cerebral glycolytic metabolism.

    PubMed

    Wisor, Jonathan P; Rempe, Michael J; Schmidt, Michelle A; Moore, Michele E; Clegern, William C

    2013-08-01

    Non-rapid eye movement sleep (NREMS) onset is characterized by a reduction in cerebral metabolism and an increase in slow waves, 1-4-Hz oscillations between relatively depolarized and hyperpolarized states in the cerebral cortex. The metabolic consequences of slow-wave activity (SWA) at the cellular level remain uncertain. We sought to determine whether SWA modulates the rate of glycolysis within the cerebral cortex. The real-time measurement of lactate concentration in the mouse cerebral cortex demonstrates that it increases during enforced wakefulness. In spontaneous sleep/wake cycles, lactate concentration builds during wakefulness and rapid eye movement sleep and declines during NREMS. The rate at which lactate concentration declines during NREMS is proportional to the magnitude of electroencephalographic (EEG) activity at frequencies of <10 Hz. The induction of 1-Hz oscillations, but not 10-Hz oscillations, in the electroencephalogram by optogenetic stimulation of cortical pyramidal cells during wakefulness triggers a decline in lactate concentration. We conclude that cerebral SWA promotes a decline in the rate of glycolysis in the cerebral cortex. These results demonstrate a cellular energetic function for sleep SWA, which may contribute to its restorative effects on brain function. PMID:22767634

  16. Developmental aspects of sleep slow waves: linking sleep, brain maturation and behavior.

    PubMed

    Ringli, Maya; Huber, Reto

    2011-01-01

    Sleep slow waves are the major electrophysiological features of non-rapid eye movement (NREM) sleep. Although there is growing understanding of where slow waves originate and how they are generated during sleep, the function of slow waves is still largely unclear. A recently proposed hypothesis relates slow waves to the homeostatic regulation of synaptic plasticity. While several studies confirm a correlation between experimentally triggered synaptic changes and slow-wave activity (SWA), little is known about its association to synaptic changes occurring during cortical maturation. Interestingly, slow waves undergo remarkable changes during development that parallel the time course of cortical maturation. In a recent cross-sectional study including children and adolescents, the topographical distribution of SWA was analyzed with high-density electroencephalography. The results showed age-dependent differences in SWA topography: SWA was highest over posterior regions during early childhood and then shifted over central derivations to the frontal cortex in late adolescence. This trajectory of SWA topography matches the course of cortical gray maturation. In this chapter, the major changes in slow waves during development are highlighted and linked to cortical maturation and behavior. Interestingly, synaptic density and slow-wave amplitude increase during childhood are highest shortly before puberty, decline thereafter during adolescence, reaching overall stable levels during adulthood. The question arises whether SWA is merely reflecting cortical changes or if it plays an active role in brain maturation. We thereby propose a model, by which sleep slow waves may contribute to cortical maturation. We hypothesize that while there is a balance between synaptic strengthening and synaptic downscaling in adults, the balance of strengthening/formation and weakening/elimination is tilted during development. PMID:21854956

  17. Cortical thinning explains changes in sleep slow waves during adulthood.

    PubMed

    Dubé, Jonathan; Lafortune, Marjolaine; Bedetti, Christophe; Bouchard, Maude; Gagnon, Jean François; Doyon, Julien; Evans, Alan C; Lina, Jean-Marc; Carrier, Julie

    2015-05-20

    Sleep slow waves (SWs) change considerably throughout normal aging. In humans, SWs are generated and propagate on a structural backbone of highly interconnected cortical regions that form most of the default mode network, such as the insula, cingulate cortices, temporal lobe, parietal lobe, and medial frontal lobe. Regions in this network undergo cortical thinning and breakdown in structural and functional connectivity over the course of normal aging. In this study, we investigated how changes in cortical thickness (CT), a measure of gray matter integrity, are involved in modifications of sleep SWs during adulthood in humans. Thirty young (mean age = 23.49 years; SD = 2.79) and 33 older (mean age = 60.35 years; SD = 5.71) healthy subjects underwent a nocturnal polysomnography and T1 MRI. We show that, when controlling for age, higher SW density (nb/min of nonrapid eye movement sleep) was associated with higher CT in cortical regions involved in SW generation surrounding the lateral fissure (insula, superior temporal, parietal, middle frontal), whereas higher SW amplitude was associated with higher CT in middle frontal, medial prefrontal, and medial posterior regions. Mediation analyses demonstrated that thinning in a network of cortical regions involved in SW generation and propagation, but also in cognitive functions, explained the age-related decrease in SW density and amplitude. Altogether, our results suggest that microstructural degradation of specific cortical regions compromise SW generation and propagation in older subjects, critically contributing to age-related changes in SW oscillations. PMID:25995467

  18. Effects of aging on slow-wave sleep dynamics and human spatial navigational memory consolidation.

    PubMed

    Varga, Andrew W; Ducca, Emma L; Kishi, Akifumi; Fischer, Esther; Parekh, Ankit; Koushyk, Viachaslau; Yau, Po Lai; Gumb, Tyler; Leibert, David P; Wohlleber, Margaret E; Burschtin, Omar E; Convit, Antonio; Rapoport, David M; Osorio, Ricardo S; Ayappa, Indu

    2016-06-01

    The consolidation of spatial navigational memory during sleep is supported by electrophysiological and behavioral evidence. The features of sleep that mediate this ability may change with aging, as percentage of slow-wave sleep is canonically thought to decrease with age, and slow waves are thought to help orchestrate hippocampal-neocortical dialog that supports systems level consolidation. In this study, groups of younger and older subjects performed timed trials before and after polysomnographically recorded sleep on a 3D spatial maze navigational task. Although younger subjects performed better than older subjects at baseline, both groups showed similar improvement across presleep trials. However, younger subjects experienced significant improvement in maze performance during sleep that was not observed in older subjects, without differences in morning psychomotor vigilance between groups. Older subjects had sleep quality marked by decreased amount of slow-wave sleep and increased fragmentation of slow-wave sleep, resulting in decreased slow-wave activity. Across all subjects, frontal slow-wave activity was positively correlated with both overnight change in maze performance and medial prefrontal cortical volume, illuminating a potential neuroanatomical substrate for slow-wave activity changes with aging and underscoring the importance of slow-wave activity in sleep-dependent spatial navigational memory consolidation. PMID:27143431

  19. Midlife Decline in Declarative Memory Consolidation Is Correlated with a Decline in Slow Wave Sleep

    ERIC Educational Resources Information Center

    Backhaus, Jutta; Born, Jan; Hoeckesfeld, Ralf; Fokuhl, Sylvia; Hohagen, Fritz; Junghanns, Klaus

    2007-01-01

    Sleep architecture as well as memory function are strongly age dependent. Slow wave sleep (SWS), in particular, decreases dramatically with increasing age, starting already beyond the age of 30. SWS normally predominates during early nocturnal sleep and is implicated in declarative memory consolidation. However, the consequences of changes in…

  20. Propagated infra-slow intrinsic brain activity reorganizes across wake and slow wave sleep

    PubMed Central

    Mitra, Anish; Snyder, Abraham Z; Tagliazucchi, Enzo; Laufs, Helmut; Raichle, Marcus E

    2015-01-01

    Propagation of slow intrinsic brain activity has been widely observed in electrophysiogical studies of slow wave sleep (SWS). However, in human resting state fMRI (rs-fMRI), intrinsic activity has been understood predominantly in terms of zero-lag temporal synchrony (functional connectivity) within systems known as resting state networks (RSNs). Prior rs-fMRI studies have found that RSNs are generally preserved across wake and sleep. Here, we use a recently developed analysis technique to study propagation of infra-slow intrinsic blood oxygen level dependent (BOLD) signals in normal adults during wake and SWS. This analysis reveals marked changes in propagation patterns in SWS vs. wake. Broadly, ordered propagation is preserved within traditionally defined RSNs but lost between RSNs. Additionally, propagation between cerebral cortex and subcortical structures reverses directions, and intra-cortical propagation becomes reorganized, especially in visual and sensorimotor cortices. These findings show that propagated rs-fMRI activity informs theoretical accounts of the neural functions of sleep. DOI: http://dx.doi.org/10.7554/eLife.10781.001 PMID:26551562

  1. Two features of sleep slow waves: homeostatic and reactive aspects--from long term to instant sleep homeostasis.

    PubMed

    Halász, Péter; Bódizs, Róbert; Parrino, Liborio; Terzano, Mario

    2014-10-01

    In this paper we reviewed results of sleep research that have changed the views about sleep slow wave homeostasis, which involve use-dependent and experience-dependent local aspects to understand more of the physiology of plastic changes during sleep. Apart from the traditional homeostatic slow-wave economy, we also overviewed research on the existence and role of reactive aspects of sleep slow waves. Based on the results from spontaneous and artificially evoked slow waves, we offer a new hypothesis on instant slow wave homeostatic regulation. This regulation compensates for any potentially sleep-disturbing events by providing instant "delta injections" to maintain the nightly delta level, thus protecting cognitive functions located in the frontal lobe. We suggest that this double (long-term /instant) homeostasis provides double security for the frontal lobes in order to protect cognitive functions. The incorporation of reactive slow wave activity (SWA) makes sleep regulation more dynamic and provides more room for the internalization of external influences during sleep. PMID:25192672

  2. Slow wave activity and slow oscillations in sleepwalkers and controls: effects of 38 h of sleep deprivation.

    PubMed

    Perrault, Rosemarie; Carrier, Julie; Desautels, Alex; Montplaisir, Jacques; Zadra, Antonio

    2013-08-01

    Sleepwalkers have been shown to have an unusually high number of arousals from slow wave sleep and lower slow wave activity (SWA) power during the night than controls. Because sleep deprivation increases the frequency of slow wave sleep (SWS) arousals in sleepwalkers, it may also affect the expression of the homeostatic process to a greater extent than shown previously. We thus investigated SWA power as well as slow wave oscillation (SWO) density in 10 sleepwalkers and nine controls at baseline and following 38 h of sleep deprivation. There was a significant increase in SWA during participants' recovery sleep, especially during their second non-rapid eye movement (NREM) period. SWO density was similarly increased during recovery sleep's first two NREM periods. A fronto-central gradient in SWA and SWO was also present on both nights. However, no group differences were noted on any of the 2 nights on SWA or SWO. This unexpected result may be related to the heterogeneity of sleepwalkers as a population, as well as our small sample size. SWA pressure after extended sleep deprivation may also result in a ceiling effect in both sleepwalkers and controls. PMID:23398262

  3. Complementary roles of slow-wave sleep and rapid eye movement sleep in emotional memory consolidation.

    PubMed

    Cairney, Scott A; Durrant, Simon J; Power, Rebecca; Lewis, Penelope A

    2015-06-01

    Although rapid eye movement sleep (REM) is regularly implicated in emotional memory consolidation, the role of slow-wave sleep (SWS) in this process is largely uncharacterized. In the present study, we investigated the relative impacts of nocturnal SWS and REM upon the consolidation of emotional memories using functional magnetic resonance imaging (fMRI) and polysomnography (PSG). Participants encoded emotionally positive, negative, and neutral images (remote memories) before a night of PSG-monitored sleep. Twenty-four hours later, they encoded a second set of images (recent memories) immediately before a recognition test in an MRI scanner. SWS predicted superior memory for remote negative images and a reduction in right hippocampal responses during the recollection of these items. REM, however, predicted an overnight increase in hippocampal-neocortical connectivity associated with negative remote memory. These findings provide physiological support for sequential views of sleep-dependent memory processing, demonstrating that SWS and REM serve distinct but complementary functions in consolidation. Furthermore, these findings extend those ideas to emotional memory by showing that, once selectively reorganized away from the hippocampus during SWS, emotionally aversive representations undergo a comparably targeted process during subsequent REM. PMID:24408956

  4. Neuronal Networks in Children with Continuous Spikes and Waves during Slow Sleep

    ERIC Educational Resources Information Center

    Siniatchkin, Michael; Groening, Kristina; Moehring, Jan; Moeller, Friederike; Boor, Rainer; Brodbeck, Verena; Michel, Christoph M.; Rodionov, Roman; Lemieux, Louis; Stephani, Ulrich

    2010-01-01

    Epileptic encephalopathy with continuous spikes and waves during slow sleep is an age-related disorder characterized by the presence of interictal epileptiform discharges during at least greater than 85% of sleep and cognitive deficits associated with this electroencephalography pattern. The pathophysiological mechanisms of continuous spikes and…

  5. Slow-wave oscillations in a corticothalamic model of sleep and wake.

    PubMed

    Zhao, X; Kim, J W; Robinson, P A

    2015-04-01

    A physiologically-based corticothalamic neural field model is used to study slow wave oscillations including cortical UP and DOWN states in deep sleep by extending it to incorporate bursting dynamics of neurons in the thalamic reticular nucleus. The interplay of local bursting dynamics and network interactions produces the cortical UP and DOWN states of slow wave sleep while preserving previously verified model predictions in the wake state. Results show that EEG spectral features in wake and sleep are reproduced. The bursting is subthreshold but acts to intensify the amplitude of oscillations in slow wave sleep with deep UP/DOWN oscillations on the cortex emerging naturally. Furthermore, there is a continuous cycle between the two regimes, rather than a flip-flop between discrete states. PMID:25659479

  6. The occurrence of individual slow waves in sleep is predicted by heart rate.

    PubMed

    Mensen, Armand; Zhang, Zhongxing; Qi, Ming; Khatami, Ramin

    2016-01-01

    The integration of near-infrared spectroscopy and electroencephalography measures presents an ideal method to study the haemodynamics of sleep. While the cortical dynamics and neuro-modulating influences affecting the transition from wakefulness to sleep is well researched, the assumption has been that individual slow waves, the hallmark of deep sleep, are spontaneously occurring cortical events. By creating event-related potentials from the NIRS recording, time-locked to the onset of thousands of individual slow waves, we show the onset of slow waves is phase-locked to an ongoing oscillation in the NIRS recording. This oscillation stems from the moment to moment fluctuations of light absorption caused by arterial pulsations driven by the heart beat. The same oscillating signal can be detected if the electrocardiogram is time-locked to the onset of the slow wave. The ongoing NIRS oscillation suggests that individual slow wave initiation is dependent on that signal, and not the other way round. However, the precise causal links remain speculative. We propose several potential mechanisms: that the heart-beat or arterial pulsation acts as a stimulus which evokes a down-state; local fluctuations in energy supply may lead to a network effect of hyperpolarization; that the arterial pulsations lead to corresponding changes in the cerebral-spinal-fluid which evokes the slow wave; or that a third neural generator, regulating heart rate and slow waves may be involved. PMID:27445083

  7. The occurrence of individual slow waves in sleep is predicted by heart rate

    PubMed Central

    Mensen, Armand; Zhang, Zhongxing; Qi, Ming; Khatami, Ramin

    2016-01-01

    The integration of near-infrared spectroscopy and electroencephalography measures presents an ideal method to study the haemodynamics of sleep. While the cortical dynamics and neuro-modulating influences affecting the transition from wakefulness to sleep is well researched, the assumption has been that individual slow waves, the hallmark of deep sleep, are spontaneously occurring cortical events. By creating event-related potentials from the NIRS recording, time-locked to the onset of thousands of individual slow waves, we show the onset of slow waves is phase-locked to an ongoing oscillation in the NIRS recording. This oscillation stems from the moment to moment fluctuations of light absorption caused by arterial pulsations driven by the heart beat. The same oscillating signal can be detected if the electrocardiogram is time-locked to the onset of the slow wave. The ongoing NIRS oscillation suggests that individual slow wave initiation is dependent on that signal, and not the other way round. However, the precise causal links remain speculative. We propose several potential mechanisms: that the heart-beat or arterial pulsation acts as a stimulus which evokes a down-state; local fluctuations in energy supply may lead to a network effect of hyperpolarization; that the arterial pulsations lead to corresponding changes in the cerebral-spinal-fluid which evokes the slow wave; or that a third neural generator, regulating heart rate and slow waves may be involved. PMID:27445083

  8. Slow wave sleep-inducing effects of first generation H1-antagonists.

    PubMed

    Saitou, K; Kaneko, Y; Sugimoto, Y; Chen, Z; Kamei, C

    1999-10-01

    The present study was performed to see if first-generation histamine H1-antagonists are useful sedative-hypnotic drugs. Increases in electroencephalogram (EEG) power spectra of the delta band (0-4 Hz) at the frontal cortex and theta band (4-8 Hz) at the hippocampus in rats were used as an indexes of sleep. The H1-antagonists used in this study resulted in a decrease in sleep latency and an increase in sleep duration (slow wave sleep). The rate of REM (rapid eye movement) sleep during slow wave sleep was decreased by H1-antagonists and brotizolam. The order of potency of H1-antagonists for the reduction in sleep latency (from greatest to least) was promethazine>chlorpheniramine>diphenhydramine and pyrilamine, and that for the increase in sleep duration was chlorpheniramine>promethazine>diphenhydramine and pyrilamine. Brotizolam was more potent than these H1-antagonists, with 14-18-fold and 4-14-fold greater effects on sleep latency and duration, respectively. These results clearly show that H1-antagonists are effective in mild to moderate insomnia as sedative-hypnotic drugs. PMID:10549859

  9. Human longevity is associated with regular sleep patterns, maintenance of slow wave sleep, and favorable lipid profile

    PubMed Central

    Mazzotti, Diego Robles; Guindalini, Camila; Moraes, Walter André dos Santos; Andersen, Monica Levy; Cendoroglo, Maysa Seabra; Ramos, Luiz Roberto; Tufik, Sergio

    2014-01-01

    Some individuals are able to successfully reach very old ages, reflecting higher adaptation against age-associated effects. Sleep is one of the processes deeply affected by aging; however few studies evaluating sleep in long-lived individuals (aged over 85) have been reported to date. The aim of this study was to characterize the sleep patterns and biochemical profile of oldest old individuals (N = 10, age 85–105 years old) and compare them to young adults (N = 15, age 20–30 years old) and older adults (N = 13, age 60–70 years old). All subjects underwent full-night polysomnography, 1-week of actigraphic recording and peripheral blood collection. Sleep electroencephalogram spectral analysis was also performed. The oldest old individuals showed lower sleep efficiency and REM sleep when compared to the older adults, while stage N3 percentage and delta power were similar across the groups. Oldest old individuals maintained strictly regular sleep-wake schedules and also presented higher HDL-cholesterol and lower triglyceride levels than older adults. The present study revealed novel data regarding specific sleep patterns and maintenance of slow wave sleep in the oldest old group. Taken together with the favorable lipid profile, these results contribute with evidence to the importance of sleep and lipid metabolism regulation in the maintenance of longevity in humans. PMID:25009494

  10. Altered Neural Responses to Sounds in Primate Primary Auditory Cortex during Slow-Wave Sleep

    PubMed Central

    Issa, Elias B.

    2011-01-01

    How sounds are processed by the brain during sleep is an important question for understanding how we perceive the sensory environment in this unique behavioral state. While human behavioral data have indicated selective impairments of sound processing during sleep, brain imaging and neurophysiology studies have reported that overall neural activity in auditory cortex during sleep is surprisingly similar to that during wakefulness. This responsiveness to external stimuli leaves open the question of how neural responses during sleep differ, if at all, from wakefulness. Using extracellular neural recordings in the primary auditory cortex of naturally sleeping common marmosets, we show that slow-wave sleep (SWS) alters neural responses in the primate auditory cortex in two specific ways. SWS reduced the sensitivity of auditory cortex such that quiet sounds elicited weak responses in SWS compared with wakefulness, while loud sounds evoked similar responses in SWS and wakefulness. Furthermore, SWS reduced the extent of sound-evoked response suppression. This pattern of alterations was not observed during rapid eye movement sleep and could not be easily explained by the presence of slow rhythms in SWS. The alteration of excitatory and inhibitory responses during SWS suggests limitations in auditory processing and provides novel insights for understanding why certain sounds are processed while others are missed during deep sleep. PMID:21414918

  11. Involvement of Spindles in Memory Consolidation Is Slow Wave Sleep-Specific

    ERIC Educational Resources Information Center

    Cox, Roy; Hofman, Winni F.; Talamini, Lucia M.

    2012-01-01

    Both sleep spindles and slow oscillations have been implicated in sleep-dependent memory consolidation. Whereas spindles occur during both light and deep sleep, slow oscillations are restricted to deep sleep, raising the possibility of greater consolidation-related spindle involvement during deep sleep. We assessed declarative memory retention…

  12. Sustained increase in hippocampal sharp-wave ripple activity during slow-wave sleep after learning

    PubMed Central

    Eschenko, Oxana; Ramadan, Wiâm; Mölle, Matthias; Born, Jan; Sara, Susan J.

    2008-01-01

    High-frequency oscillations, known as sharp-wave/ripple (SPW-R) complexes occurring in hippocampus during slow-wave sleep (SWS), have been proposed to promote synaptic plasticity necessary for memory consolidation. We recorded sleep for 3 h after rats were trained on an odor-reward association task. Learning resulted in an increased number SPW-Rs during the first hour of post-learning SWS. The magnitude of ripple events and their duration were also elevated for up to 2 h after the newly formed memory. Rats that did not learn the discrimination during the training session did not show any change in SPW-Rs. Successful retrieval from remote memory was likewise accompanied by an increase in SPW-R density and magnitude, relative to the previously recorded baseline, but the effects were much shorter lasting and did not include increases in ripple duration and amplitude. A short-lasting increase of ripple activity was also observed when rats were rewarded for performing a motor component of the task only. There were no increases in ripple activity after habituation to the experimental environment. These experiments show that the characteristics of hippocampal high-frequency oscillations during SWS are affected by prior behavioral experience. Associative learning induces robust and sustained (up to 2 h) changes in several SPW-R characteristics, while after retrieval from remote memory or performance of a well-trained procedural aspect of the task, only transient changes in ripple density were induced. PMID:18385477

  13. Targeted Memory Reactivation During Slow Wave Sleep Facilitates Emotional Memory Consolidation

    PubMed Central

    Cairney, Scott A.; Durrant, Simon J.; Hulleman, Johan; Lewis, Penelope A.

    2014-01-01

    Study Objectives: To investigate the mechanisms by which auditory targeted memory reactivation (TMR) during slow wave sleep (SWS) influences the consolidation of emotionally negative and neutral memories. Design: Each of 72 (36 negative, 36 neutral) picture-location associations were encoded with a semantically related sound. During a subsequent nap, half of the sounds were replayed in SWS, before picture-location recall was examined in a final test. Setting: Manchester Sleep Laboratory, University of Manchester. Participants: 15 adults (3 male) mean age = 20.40 (standard deviation ± 3.07). Interventions: TMR with auditory cues during SWS. Measurements and Results: Performance was assessed by memory accuracy and recall response times (RTs). Data were analyzed with a 2 (sound: replayed/not replayed) × 2 (emotion: negative/neutral) repeated measures analysis of covariance with SWS duration, and then SWS spindles, as the mean-centered covariate. Both analyses revealed a significant three-way interaction for RTs but not memory accuracy. Critically, SWS duration and SWS spindles predicted faster memory judgments for negative, relative to neutral, picture locations that were cued with TMR. Conclusions: TMR initiates an enhanced consolidation process during subsequent SWS, wherein sleep spindles mediate the selective enhancement of reactivated emotional memories. Citation: Cairney SA; Durrant SJ; Hulleman J; Lewis PA. Targeted memory reactivation during slow wave sleep facilitates emotional memory consolidation. SLEEP 2014;37(4):701-707. PMID:24688163

  14. Neurons of visual cortex respond to visceral stimulation during slow wave sleep.

    PubMed

    Pigarev, I N

    1994-10-01

    It is hypothesized here that the same cortical areas which process signals from exteroreceptors (visual, acoustic, etc.) in wakefulness process signals from visceral organs during sleep. To check this hypothesis, the activity of 49 neurons (hypercomplex, complex and simple, as defined by conventional visual stimulation) was recorded from visual areas V1 and V2 in chronic cats at different stages of the sleep-waking cycle. Neuronal responses to electrical stimulation of the area of stomach and small intestine (single pulses of 100-500 microA. 0.5 ms duration) were investigated. It was found that intraperitoneal stimulation delivered during slow wave sleep evoked clear excitatory responses in most simple and complex cells. In hypercomplex cells, only inhibitory responses were observed. All these responses disappeared in wakefulness. These observations are compatible with the above hypothesis. PMID:7845596

  15. Dissociating the contributions of slow-wave sleep and rapid eye movement sleep to emotional item and source memory.

    PubMed

    Groch, S; Zinke, K; Wilhelm, I; Born, J

    2015-07-01

    Sleep benefits the consolidation of emotional memories, and this influence is commonly attributed to the rapid eye movement (REM) stage of sleep. However, the contributions of sleep stages to memory for an emotional episode may differ for the event per se (i.e., item memory), and the context in which it occurred (source memory). Here, we examined the effects of slow wave sleep (SWS) and REM sleep on the consolidation of emotionally negative and neutral item (picture recognition) and source memory (recall of picture-location and picture-frame color association) in humans. In Study 1, the participants (n=18) learned 48 negative and 48 neutral pictures which were presented at specific locations and preceded by colored frames that had to be associated with the picture. In a within-subject design, learning was either followed by a 3-h early-night SWS-rich or by a late-night REM sleep-rich retention interval, then retrieval was tested. Only after REM-rich sleep, and not after SWS-rich sleep, was there a significant emotional enhancement, i.e., a significantly superior retention of emotional over neutral pictures. On the other hand, after SWS-rich sleep the retention of picture-frame color associations was better than after REM-rich sleep. However, this benefit was observed only for neutral pictures; and it was completely absent for the emotional pictures. To examine whether this absent benefit reflected a suppressive effect of emotionality on associations of minor task relevance, in Study 2 we manipulated the relevance of the picture-frame color association by combining it with information about monetary reward, following otherwise comparable procedures. Here, rewarded picture-frame color associations were equally well retained over SWS-rich early sleep no matter if the frames were associated with emotional or neutral pictures. Results are consistent with the view that REM sleep favors the emotional enhancement of item memory whereas SWS appears to contribute primarily

  16. Heightened Delta Power during Slow-Wave-Sleep in Patients with Rett Syndrome Associated with Poor Sleep Efficiency

    PubMed Central

    Ammanuel, Simon; Chan, Wesley C.; Adler, Daniel A.; Lakshamanan, Balaji M.; Gupta, Siddharth S.; Ewen, Joshua B.; Johnston, Michael V.; Marcus, Carole L.; Naidu, Sakkubai; Kadam, Shilpa D.

    2015-01-01

    Sleep problems are commonly reported in Rett syndrome (RTT); however the electroencephalographic (EEG) biomarkers underlying sleep dysfunction are poorly understood. The aim of this study was to analyze the temporal evolution of quantitative EEG (qEEG) biomarkers in overnight EEGs recorded from girls (2–9 yrs. old) diagnosed with RTT using a non-traditional automated protocol. In this study, EEG spectral analysis identified high delta power cycles representing slow wave sleep (SWS) in 8–9h overnight sleep EEGs from the frontal, central and occipital leads (AP axis), comparing age-matched girls with and without RTT. Automated algorithms quantitated the area under the curve (AUC) within identified SWS cycles for each spectral frequency wave form. Both age-matched RTT and control EEGs showed similar increasing trends for recorded delta wave power in the EEG leads along the antero-posterior (AP). RTT EEGs had significantly fewer numbers of SWS sleep cycles; therefore, the overall time spent in SWS was also significantly lower in RTT. In contrast, the AUC for delta power within each SWS cycle was significantly heightened in RTT and remained heightened over consecutive cycles unlike control EEGs that showed an overnight decrement of delta power in consecutive cycles. Gamma wave power associated with these SWS cycles was similar to controls. However, the negative correlation of gamma power with age (r = -.59; p<0.01) detected in controls (2–5 yrs. vs. 6–9 yrs.) was lost in RTT. Poor % SWS (i.e., time spent in SWS overnight) in RTT was also driven by the younger age-group. Incidence of seizures in RTT was associated with significantly lower number of SWS cycles. Therefore, qEEG biomarkers of SWS in RTT evolved temporally and correlated significantly with clinical severity. PMID:26444000

  17. Antidepressant Effects of Selective Slow Wave Sleep Deprivation in Major Depression: A High-Density EEG Investigation

    PubMed Central

    Landsness, Eric C.; Goldstein, Michael R.; Peterson, Michael J.; Tononi, Giulio; Benca, Ruth M.

    2011-01-01

    Sleep deprivation can acutely reverse depressive symptoms in some patients with major depression. Because abnormalities in slow wave sleep are one of the most consistent biological markers of depression, it is plausible that the antidepressant effects of sleep deprivation are due to the effects on slow wave homeostasis. This study tested the prediction that selectively reducing slow waves during sleep (slow wave deprivation; SWD), without disrupting total sleep time, will lead to an acute reduction in depressive symptomatology. As part of a multi-night, cross-over design study, participants with major depression (non-medicated; n = 17) underwent baseline, SWD, and recovery sleep sessions, and were recorded with high-density EEG (hdEEG). During SWD, acoustic stimuli were played to suppress subsequent slow waves, without waking up the participant. The effects of SWD on depressive symptoms were assessed with both self-rated and researcher-administered scales. Participants experienced a significant decrease in depressive symptoms according to both self-rated (p = .007) and researcher-administered (p = .010) scales, while vigilance was unaffected. The reduction in depressive symptoms correlated with the overnight dissipation of fronto-central slow wave activity (SWA) on baseline sleep, the rebound in right frontal all-night SWA on recovery sleep, and the amount of REM sleep on the SWD night. In addition to highlighting the benefits of hdEEG in detecting regional changes in brain activity, these findings suggest that SWD may help to better understand the pathophysiology of depression and may be a useful tool for the neuromodulatory reversal of depressive symptomatology. PMID:21397252

  18. Increased frontal sleep slow wave activity in adolescents with major depression

    PubMed Central

    Tesler, Noemi; Gerstenberg, Miriam; Franscini, Maurizia; Jenni, Oskar G.; Walitza, Susanne; Huber, Reto

    2015-01-01

    Sleep slow wave activity (SWA), the major electrophysiological characteristic of deep sleep, mirrors both cortical restructuring and functioning. The incidence of Major Depressive Disorder (MDD) substantially rises during the vulnerable developmental phase of adolescence, where essential cortical restructuring is taking place. The goal of this study was to assess characteristics of SWA topography in adolescents with MDD, in order to assess abnormalities in both cortical restructuring and functioning on a local level. All night high-density EEG was recorded in 15 patients meeting DSM-5 criteria for MDD and 15 sex- and age-matched healthy controls. The actual symptom severity was assessed using the Children's Depression Rating Scale—Revised (CDRS-R). Topographical power maps were calculated based on the average SWA of the first non-rapid eye movement (NREM) sleep episode. Depressed adolescents exhibited significantly more SWA in a cluster of frontal electrodes compared to controls. SWA over frontal brain regions correlated positively with the CDRS-R subscore “morbid thoughts”. Self-reported sleep latency was significantly higher in depressed adolescents compared to controls whereas sleep architecture did not differ between the groups. Higher frontal SWA in depressed adolescents may represent a promising biomarker tracing cortical regions of intense use and/or restructuring. PMID:26870661

  19. Development of the brain's default mode network from wakefulness to slow wave sleep.

    PubMed

    Sämann, Philipp G; Wehrle, Renate; Hoehn, David; Spoormaker, Victor I; Peters, Henning; Tully, Carolin; Holsboer, Florian; Czisch, Michael

    2011-09-01

    Falling asleep is paralleled by a loss of conscious awareness and reduced capacity to process external stimuli. Little is known on sleep-associated changes of spontaneously synchronized anatomical networks as detected by resting-state functional magnetic resonance imaging (rs-fMRI). We employed functional connectivity analysis of rs-fMRI series obtained from 25 healthy participants, covering all non-rapid eye movement (NREM) sleep stages. We focused on the default mode network (DMN) and its anticorrelated network (ACN) that are involved in internal and external awareness during wakefulness. Using independent component analysis, cross-correlation analysis (CCA), and intraindividual dynamic network tracking, we found significant changes in DMN/ACN integrity throughout the NREM sleep. With increasing sleep depth, contributions of the posterior cingulate cortex (PCC)/retrosplenial cortex (RspC), parahippocampal gyrus, and medial prefrontal cortex to the DMN decreased. CCA revealed a breakdown of corticocortical functional connectivity, particularly between the posterior and anterior midline node of the DMN and the DMN and the ACN. Dynamic tracking of the DMN from wakefulness into slow wave sleep in a single subject added insights into intraindividual network fluctuations. Results resonate with a role of the PCC/RspC for the regulation of consciousness. We further submit that preserved corticocortical synchronization could represent a prerequisite for maintaining internal and external awareness. PMID:21330468

  20. Reactivation of emergent task-related ensembles during slow-wave sleep after neuroprosthetic learning.

    PubMed

    Gulati, Tanuj; Ramanathan, Dhakshin S; Wong, Chelsea C; Ganguly, Karunesh

    2014-08-01

    Brain-machine interfaces can allow neural control over assistive devices. They also provide an important platform for studying neural plasticity. Recent studies have suggested that optimal engagement of learning is essential for robust neuroprosthetic control. However, little is known about the neural processes that may consolidate a neuroprosthetic skill. On the basis of the growing body of evidence linking slow-wave activity (SWA) during sleep to consolidation, we examined whether there is 'offline' processing after neuroprosthetic learning. Using a rodent model, we found that, after successful learning, task-related units specifically experienced increased locking and coherency to SWA during sleep. Moreover, spike-spike coherence among these units was substantially enhanced. These changes were not present with poor skill acquisition or after control awake periods, demonstrating the specificity of our observations to learning. Notably, the time spent in SWA predicted the performance gains. Thus, SWA appears to be involved in offline processing after neuroprosthetic learning. PMID:24997761

  1. Fragmentation of slow wave sleep after onset of complete locked-in state.

    PubMed

    Soekadar, Surjo R; Born, Jan; Birbaumer, Niels; Bensch, Michael; Halder, Sebastian; Murguialday, Ander Ramos; Gharabaghi, Alireza; Nijboer, Femke; Schölkopf, Bernhard; Martens, Suzanne

    2013-09-15

    Locked-in syndrome (LIS) as a result of brainstem lesions or progressive neurodegenerative disorders, such as amyotrophic lateral sclerosis (ALS), is a severe medical condition in which a person is fully conscious but unable to move or talk. LIS can transition into complete locked-in syndrome (CLIS) in which residual abilities to communicate through muscle twitches are entirely lost. It is unknown how CLIS affects circadian rhythm and sleep/wake patterns. Here we report a 39-year-old ALS patient who transitioned from LIS to CLIS while brain activity was continuously recorded using electrocorticography (ECoG) over one month. While we found no circadian rhythm in heart rate and body temperature, transition into CLIS was associated with increased fragmentation of slow wave sleep (SWS) across the day. Total time in SWS did not change. SWS fragmentation might reflect progressive circadian system impairment and should be considered as a factor further limiting communication capabilities in these patients. PMID:23997708

  2. Sharp wave-associated synchronized inputs from the piriform cortex activate olfactory tubercle neurons during slow-wave sleep

    PubMed Central

    Narikiyo, Kimiya; Manabe, Hiroyuki

    2013-01-01

    During slow-wave sleep, anterior piriform cortex neurons show highly synchronized discharges that accompany olfactory cortex sharp waves (OC-SPWs). The OC-SPW-related synchronized activity of anterior piriform cortex neurons travel down to the olfactory bulb and is thought to be involved in the reorganization of bulbar neuronal circuitry. However, influences of the OC-SPW-related activity on other regions of the central olfactory system are still unknown. Olfactory tubercle is an area of OC and part of ventral striatum that plays a key role in reward-directed motivational behaviors. In this study, we show that in freely behaving rats, olfactory tubercle receives OC-SPW-associated synchronized inputs during slow-wave sleep. Local field potentials in the olfactory tubercle showed SPW-like activities that were in synchrony with OC-SPWs. Single-unit recordings showed that a subpopulation of olfactory tubercle neurons discharged in synchrony with OC-SPWs. Furthermore, correlation analysis of spike activity of anterior piriform cortex and olfactory tubercle neurons revealed that the discharges of anterior piriform cortex neurons tended to precede those of olfactory tubercle neurons. Current source density analysis in urethane-anesthetized rats indicated that the current sink of the OC-SPW-associated input was located in layer III of the olfactory tubercle. These results indicate that OC-SPW-associated synchronized discharges of piriform cortex neurons travel to the deep layer of the olfactory tubercle and drive discharges of olfactory tubercle neurons. The entrainment of olfactory tubercle neurons in the OC-SPWs suggests that OC-SPWs coordinate reorganization of neuronal circuitry across wide areas of the central olfactory system including olfactory tubercle during slow-wave sleep. PMID:24108798

  3. A biphasic daily pattern of slow wave activity during a two-day 90-minute sleep wake schedule.

    PubMed

    Duncan, W C; Barbato, G; Fagioli, I; Garcia-Borreguero, D; Wehr, T A

    2009-12-01

    Twenty-four hour sleep patterns were measured in six healthy male volunteers during a 90-minute short sleep-wake (SW 30:60) cycle protocol for 48 hours. Sleep pressure estimates (amount of Slow Wave Sleep [SWS], SWA, and Rate of Synchronization [RoS: the rate of SWA build-up at the beginning of the NREM period]) were compared with the 24-hour patterns of body temperature (Tb24) and sleep propensity. A moderate sleep debt was incurred over the 48 hour study as indicated by decreased levels of 24 hour sleep. On day 1, ultradian patterns of REM and SWS sleep were prominent; on day 2, more prominent were circadian patterns of REM sleep, SWS, Sleep Latency, TST and Tb24. Also on Day 2, biphasic patterns of SWA and RoS were expressed, with peaks occurring during the falling and rising limbs of Tb24. The biphasic peaks in SWA and RoS may be associated with phase-specific interactions of the circadian pacemaker with the sleep homeostat during conditions of moderate sleep pressure. Further research is needed to replicate the finding and to identify biological factors that may underlie the twelve hour pattern in SWA. PMID:20162861

  4. Odors enhance slow-wave activity in non-rapid eye movement sleep.

    PubMed

    Perl, Ofer; Arzi, Anat; Sela, Lee; Secundo, Lavi; Holtzman, Yael; Samnon, Perry; Oksenberg, Arie; Sobel, Noam; Hairston, Ilana S

    2016-05-01

    Most forms of suprathreshold sensory stimulation perturb sleep. In contrast, presentation of pure olfactory or mild trigeminal odorants does not lead to behavioral or physiological arousal. In fact, some odors promote objective and subjective measures of sleep quality in humans and rodents. The brain mechanisms underlying these sleep-protective properties of olfaction remain unclear. Slow oscillations in the electroencephalogram (EEG) are a marker of deep sleep, and K complexes (KCs) are an EEG marker of cortical response to sensory interference. We therefore hypothesized that odorants presented during sleep will increase power in slow EEG oscillations. Moreover, given that odorants do not drive sleep interruption, we hypothesized that unlike other sensory stimuli odorants would not drive KCs. To test these hypotheses we used polysomnography to measure sleep in 34 healthy subjects (19 women, 15 men; mean age 26.5 ± 2.5 yr) who were repeatedly presented with odor stimuli via a computer-controlled air-dilution olfactometer over the course of a single night. Each participant was exposed to one of four odorants, lavender oil (n = 13), vetiver oil (n = 5), vanillin (n = 12), or ammonium sulfide (n = 4), for durations of 5, 10, and 20 s every 9-15 min. Consistent with our hypotheses, we found that odor presentation during sleep enhanced the power of delta (0.5-4 Hz) and slow spindle (9-12 Hz) frequencies during non-rapid eye movement sleep. The increase was proportionate to odor duration. In addition, odor presentation did not modulate the occurrence of KCs. These findings imply a sleep-promoting olfactory mechanism that may deepen sleep through driving increased slow-frequency oscillations. PMID:26888107

  5. Regional scalp EEG slow-wave synchronization during sleep cyclic alternating pattern A1 subtypes.

    PubMed

    Ferri, Raffaele; Rundo, Francesco; Bruni, Oliviero; Terzano, Mario G; Stam, Cornelis J

    2006-09-01

    The levels of EEG synchronization, in the 0.25-2.5 Hz band, during the A1 subtypes of the sleep "cyclic alternating pattern" (CAP) were measured in five healthy subjects by means of the synchronization likelihood (SL) algorithm. SL was measured for seven electrode pairs (F4-F3, C4-C3, P4-P3 for the analysis of interhemispheric SL and F4-C4, C4-P4, F3-C3, and C3-P3, for the analysis of intrahemispheric SL). During the A1 CAP subtypes, SL tended to be highest between pairs of electrodes situated over different hemispheres; in particular, SL obtained from F4-F3 was the highest, followed by that of P4-P3. These results indicate that the transient high level of synchronization in the slow-wave EEG range, during the sleep A1 CAP subtypes, is a phenomenon involving mostly the anterior parts of the brain and is probably based on interhemispheric interactions, possibly mediated by transcallosal connections. PMID:16806696

  6. Rats housed on corncob bedding show less slow-wave sleep.

    PubMed

    Leys, Laura J; McGaraughty, Steve; Radek, Richard J

    2012-11-01

    Despite the reported advantages of corncob bedding, questions have emerged about how comfortable animals find this type of bedding as a resting surface. In this study, encephalography (EEG) was used to compare the effects of corncob and aspen-chip bedding on rat slow-wave sleep (SWS). According to a facility-wide initiative, rats that were weaned on aspen-chip bedding were switched to corncob bedding in home cages and EEG recording chambers. Spontaneous EEG recordings obtained for 5 wk after the switch to corncob bedding demonstrated that rats spent significantly less time in SWS as compared with levels measured on aspen chips just prior to the bedding switch. SWS remained low even after a 5-wk acclimation period to the corncob bedding. We then acutely switched back to aspen-chip bedding in EEG recording chambers. Acute reinstatement of aspen-chip bedding during EEG recording was associated with an average 22% increase in time spent in SWS, with overall levels of SWS comparable to the levels measured on aspen chips prior to the change to corncob bedding. Aspen-chip bedding subsequently was reinstated in both home cages and EEG recording chambers, and SWS baseline levels were restored. These data raise important concerns about the effects of corncob bedding on rodents used in research. PMID:23294881

  7. [General statistical characteristics of the background firing in cat's cortical neurons during slow-wave sleep].

    PubMed

    Bibikov, N G; Pigarev, I N

    2013-03-01

    Background activity of 62 neurons in cat cerebral cortex was recorded in the state of slow-wave sleep for evaluation of the firing statistics. In according to their statistical characteristics neurons were subdivided in three groups. In the first group deviation from the Poisson process were comparatively small, and revealed as fragments of increased excitability following immediately after the refractory period. Second group demonstrated positive correlation of the neighbouring interspike intervals what was conditioned by the changes of the mean firing rate. In these neurons the number of spikes included into the bursts reduced after random permutation of the interspike intervals. The third group was characterized by the big number of spikes included into the bursts (> 15%), and number of bursts usually dropped down after random permutation. Some neurons of this group had constant interspike intervals within the bursts while in other units these intervals monotonically increased toward the end of the burst. Only limited number of neurons demonstrated maximums of the autocorrelation function corresponded to the frequency of the EEG delta activity. PMID:23789438

  8. Rats Housed on Corncob Bedding Show Less Slow-Wave Sleep

    PubMed Central

    Leys, Laura J; McGaraughty, Steve; Radek, Richard J

    2012-01-01

    Despite the reported advantages of corncob bedding, questions have emerged about how comfortable animals find this type of bedding as a resting surface. In this study, encephalography (EEG) was used to compare the effects of corncob and aspen-chip bedding on rat slow-wave sleep (SWS). According to a facility-wide initiative, rats that were weaned on aspen-chip bedding were switched to corncob bedding in home cages and EEG recording chambers. Spontaneous EEG recordings obtained for 5 wk after the switch to corncob bedding demonstrated that rats spent significantly less time in SWS as compared with levels measured on aspen chips just prior to the bedding switch. SWS remained low even after a 5-wk acclimation period to the corncob bedding. We then acutely switched back to aspen-chip bedding in EEG recording chambers. Acute reinstatement of aspen-chip bedding during EEG recording was associated with an average 22% increase in time spent in SWS, with overall levels of SWS comparable to the levels measured on aspen chips prior to the change to corncob bedding. Aspen-chip bedding subsequently was reinstated in both home cages and EEG recording chambers, and SWS baseline levels were restored. These data raise important concerns about the effects of corncob bedding on rodents used in research. PMID:23294881

  9. Characteristics and Management of Children with Continuous Spikes and Waves during Slow Sleep.

    PubMed

    Fatema, K; Rahman, M M; Begum, S

    2015-10-01

    This study was done to describe the clinical spectrum, EEG characteristics and treatment modalities in children with continuous spike and slow wave in sleep (CSWS). Ten patients with CSWS had been treated between 2012 and 2013. Mean age of the patients was 6.9 years; male female ratio was 3:2. The main etiologic group in this study was epilepsy (10), cerebral palsy (3) and brain lesion (arachnoid cyst). All the patients had prior seizure. Presenting features were abnormal behavior (4), agitation (4), aggression (4), eye blinking (2) and involuntary movement (2). Three patients had speech regression and 1 had motor regression. Regarding EEG finding, 7 out 10 cases had SWI>85% whereas, rest of them had SWI 50 to 80%. Most of the patients were resistant to two or more oral AED. The AED found to be efficacious were Midazolam drip, pulse methyl prednisolone and valproate. Eighty percent (80%) patient responded to midazolam drip. Methyl prednisolone caused 50% improvement in one patient but failed in 2 cases. In contrast to the previous studies where high dose valproic acid, levetiracetam, Injection ACTH was more efficacious, this study demonstrates significant positive result with midazolam drip. PMID:26620024

  10. Long-term history and immediate preceding state affect EEG slow wave characteristics at NREM sleep onset in C57BL/6 mice.

    PubMed

    Cui, N; Mckillop, L E; Fisher, S P; Oliver, P L; Vyazovskiy, V V

    2014-01-01

    The dynamics of cortical activity across the 24-h day and at vigilance state transitions is regulated by an interaction between global subcortical neuromodulatory influences and local shifts in network synchrony and excitability. To address the role of long-term and immediate preceding history in local and global cortical dynamics, we investigated cortical EEG recorded from both frontal and occipital regions during an undisturbed 24-h recording in mice. As expected, at the beginning of the light period, under physiologically increased sleep pressure, EEG slow waves were more frequent and had higher amplitude and slopes, compared to the rest of the light period. Within discrete NREM sleep episodes, the incidence, amplitude and slopes of individual slow waves increased progressively after episode onset in both derivations by approximately 10-30%. Interestingly, at the beginning of NREM sleep episodes slow waves in the frontal and occipital derivations frequently occurred in isolation, as quantified by longer latencies between consecutive slow waves in the two regions. Notably, slow waves during the initial period of NREM sleep following REM sleep episodes were significantly less frequent, lower in amplitude and exhibited shallower slopes, compared to those that occurred in NREM episodes after prolonged waking. Moreover, the latencies between consecutive frontal and occipital NREM slow waves were substantially longer when they occurred directly after REM sleep compared to following consolidated wakefulness. Overall these data reveal a complex picture, where both time of day and preceding state contribute to the characteristics and dynamics of slow waves within NREM sleep. These findings suggest that NREM sleep initiates in a more "local" fashion when it occurs following REM sleep episodes as opposed to sustained waking bouts. While the mechanisms and functional significance of such a re-setting of brain state after individual REM sleep episodes remains to be

  11. The dream-lag effect: Selective processing of personally significant events during Rapid Eye Movement sleep, but not during Slow Wave Sleep.

    PubMed

    van Rijn, E; Eichenlaub, J-B; Lewis, P A; Walker, M P; Gaskell, M G; Malinowski, J E; Blagrove, M

    2015-07-01

    Incorporation of details from waking life events into Rapid Eye Movement (REM) sleep dreams has been found to be highest on the night after, and then 5-7 nights after events (termed, respectively, the day-residue and dream-lag effects). In experiment 1, 44 participants kept a daily log for 10 days, reporting major daily activities (MDAs), personally significant events (PSEs), and major concerns (MCs). Dream reports were collected from REM and Slow Wave Sleep (SWS) in the laboratory, or from REM sleep at home. The dream-lag effect was found for the incorporation of PSEs into REM dreams collected at home, but not for MDAs or MCs. No dream-lag effect was found for SWS dreams, or for REM dreams collected in the lab after SWS awakenings earlier in the night. In experiment 2, the 44 participants recorded reports of their spontaneously recalled home dreams over the 10 nights following the instrumental awakenings night, which thus acted as a controlled stimulus with two salience levels, high (sleep lab) and low (home awakenings). The dream-lag effect was found for the incorporation into home dreams of references to the experience of being in the sleep laboratory, but only for participants who had reported concerns beforehand about being in the sleep laboratory. The delayed incorporation of events from daily life into dreams has been proposed to reflect REM sleep-dependent memory consolidation. However, an alternative emotion processing or emotional impact of events account, distinct from memory consolidation, is supported by the finding that SWS dreams do not evidence the dream-lag effect. PMID:25683202

  12. Epileptic encephalopathy with continuous spikes and waves in the occipito-temporal region during slow-wave sleep in two patients with acquired Kanji dysgraphia.

    PubMed

    Kuki, Ichiro; Kawawaki, Hisashi; Okazaki, Shin; Ikeda, Hiroko; Tomiwa, Kiyotaka

    2014-12-01

    We encountered two patients with acquired Kanji dysgraphia in whom continuous spikes and waves, dominant in the occipito-temporal region, were recorded during slow-wave sleep. Electrical status epileptics during sleep (ESES) was demonstrated on overnight electroencephalography, and dipoles clustered in and around the posterior inferior temporal cortex on magnetoencephalography. Functional neuroimaging suggested dysfunction in the left posterior temporal lobe, including the posterior inferior temporal cortex. The patients had normal intelligence with no problems in reading and writing Kana, as well as copying, reading aloud, and identifying Kanjis, but showed Kanji dysgraphia (morphological, phonemic, and semantic error) accompanied by impaired visual processing. ESES was resolved by sodium valproate, clonazepam, and acetazolamide in Patient 1, and by adrenocorticotropic hormone, sodium valproate, and clorazepate in Patient 2. The present cases had the unique cognitive dysfunction of Kanji dysgraphia, which is distinct from that of Landau-Kleffner syndrome and continuous spikes and waves during slow-wave sleep. However, the present cases also share common features with these two encephalopathies in terms of the clinical course, pathophysiology, neuroimaging, and response to steroids and antiepileptic drugs. In the context of the Japanese language, acquired Kanji dysgraphia may occur due to electrical dysfunction of left posterior inferior temporal cortex in patients with ESES. PMID:25333864

  13. Substance P and the neurokinin-1 receptor regulate electroencephalogram non-rapid eye movement sleep slow-wave activity locally

    PubMed Central

    Zielinski, Mark R.; Karpova, Svetlana A.; Yang, Xiaomei; Gerashchenko, Dmitry

    2014-01-01

    The neuropeptide substance P is an excitatory neurotransmitter produced by various cells including neurons and microglia that is involved in regulating inflammation and cerebral blood flow—functions that affect sleep and slow-wave activity (SWA). Substance P is the major ligand for the neurokinin-1 receptor (NK-1R), which is found throughout the brain including the cortex. The NK-1R is found on sleep-active cortical neurons expressing neuronal nitric oxide synthase whose activity is associated with SWA. We determined the effects of local cortical administration of a NK-1R agonist (substance P-fragment 1, 7) and a NK-1R antagonist (CP96345) on sleep and SWA in mice. The NK-1R agonist significantly enhanced SWA for several hours when applied locally to the cortex of the ipsilateral hemisphere as the electroencephalogram (EEG) electrode but not after application to the contralateral hemisphere when compared to saline vehicle control injections. In addition, a significant compensatory reduction in SWA was found after the NK-1R agonist-induced enhancements in SWA. Conversely, injections of the NK-1R antagonist into the cortex of the ipsilateral hemisphere of the EEG electrode attenuated SWA compared to vehicle injections but this effect was not found after injections of the NK-1R antagonist into contralateral hemisphere as the EEG electrode. Non-rapid eye movement sleep and rapid eye movement sleep duration responses after NK-1R agonist and antagonist injections were not significantly different from the responses to the vehicle. Our findings indicate that the substance P and the NK-1R are involved in regulating SWA locally. PMID:25301750

  14. Nonlinear Dynamical Systems Effects of Homeopathic Remedies on Multiscale Entropy and Correlation Dimension of Slow Wave Sleep EEG in Young Adults with Histories of Coffee-Induced Insomnia

    PubMed Central

    Bell, Iris R.; Howerter, Amy; Jackson, Nicholas; Aickin, Mikel; Bootzin, Richard R.; Brooks, Audrey J.

    2012-01-01

    Background Investigators of homeopathy have proposed that nonlinear dynamical systems (NDS) and complex systems science offer conceptual and analytic tools for evaluating homeopathic remedy effects. Previous animal studies demonstrate that homeopathic medicines alter delta electroencephalographic (EEG) slow wave sleep. The present study extended findings of remedy-related sleep stage alterations in human subjects by testing the feasibility of using two different NDS analytic approaches to assess remedy effects on human slow wave sleep EEG. Methods Subjects (N=54) were young adult male and female college students with a history of coffee-related insomnia who participated in a larger 4-week study of the polysomnographic effects of homeopathic medicines on home-based all-night sleep recordings. Subjects took one bedtime dose of a homeopathic remedy (Coffea cruda or Nux vomica 30c). We computed multiscale entropy (MSE) and the correlation dimension (Mekler-D2) for stage 3 and 4 slow wave sleep EEG sampled in artifact-free 2-minute segments during the first two rapid-eye-movement (REM) cycles for remedy and post-remedy nights, controlling for placebo and post-placebo night effects. Results MSE results indicate significant, remedy-specific directional effects, especially later in the night (REM cycle 2) (CC: remedy night increases and post-remedy night decreases in MSE at multiple sites for both stages 3 and 4 in both REM cycles; NV: remedy night decreases and post-remedy night increases, mainly in stage 3 REM cycle 2 MSE). D2 analyses yielded more sporadic and inconsistent findings. Conclusions Homeopathic medicines Coffea cruda and Nux vomica in 30c potencies alter short-term nonlinear dynamic parameters of slow wave sleep EEG in healthy young adults. MSE may provide a more sensitive NDS analytic method than D2 for evaluating homeopathic remedy effects on human sleep EEG patterns. PMID:22818237

  15. Theta-rhythmic drive between medial septum and hippocampus in slow-wave sleep and microarousal: a Granger causality analysis.

    PubMed

    Kang, D; Ding, M; Topchiy, I; Shifflett, L; Kocsis, B

    2015-11-01

    Medial septum (MS) plays a critical role in controlling the electrical activity of the hippocampus (HIPP). In particular, theta-rhythmic burst firing of MS neurons is thought to drive lasting HIPP theta oscillations in rats during waking motor activity and REM sleep. Less is known about MS-HIPP interactions in nontheta states such as non-REM sleep, in which HIPP theta oscillations are absent but theta-rhythmic burst firing in subsets of MS neurons is preserved. The present study used Granger causality (GC) to examine the interaction patterns between MS and HIPP in slow-wave sleep (SWS, a nontheta state) and during its short interruptions called microarousals (a transient theta state). We found that during SWS, while GC revealed a unidirectional MS→HIPP influence over a wide frequency band (2-12 Hz, maximum: ∼8 Hz), there was no theta peak in the hippocampal power spectra, indicating a lack of theta activity in HIPP. In contrast, during microarousals, theta peaks were seen in both MS and HIPP power spectra and were accompanied by bidirectional GC with MS→HIPP and HIPP→MS theta drives being of equal magnitude. Thus GC in a nontheta state (SWS) vs. a theta state (microarousal) primarily differed in the level of HIPP→MS. The present findings suggest a modification of our understanding of the role of MS as the theta generator in two regards. First, a MS→HIPP theta drive does not necessarily induce theta field oscillations in the hippocampus, as found in SWS. Second, HIPP theta oscillations entail bidirectional theta-rhythmic interactions between MS and HIPP. PMID:26354315

  16. Exposure to extinction-associated contextual tone during slow-wave sleep and wakefulness differentially modulates fear expression.

    PubMed

    Ai, Si-Zhi; Chen, Jie; Liu, Jian-Feng; He, Jia; Xue, Yan-Xue; Bao, Yan-Ping; Han, Fang; Tang, Xiang-Dong; Lu, Lin; Shi, Jie

    2015-09-01

    Recent research has used context cues (odor or auditory cues) to target memories during sleep and has demonstrated that they can enhance declarative and procedural memories. However, the effects of external cues re-presented during sleep on emotional memory are still not fully understood. In the present study, we conducted a Pavlovian fear conditioning/extinction paradigm and examined the effects of re-exposure to extinction memory associated contextual tones during slow-wave sleep (SWS) and wakefulness on fear expression. The participants underwent fear conditioning on the first day, during which colored squares served as the conditioned stimulus (CS) and a mild shock served as the unconditioned stimulus (US). The next day, they underwent extinction, during which the CSs were presented without the US but accompanied by a contextual tone (pink noise). Immediately after extinction, the participants were required to take a nap or remain awake and randomly assigned to six groups. Four of the groups were separately exposed to the associated tone (i.e. SWS-Tone group and Wake-Tone group) or an irrelevant tone (control tone, CtrT) (i.e. SWS-CtrT group and Wake-CtrT group), while the other two groups were not (i.e. SWS-No Tone group and Wake-No Tone group). Subsequently, the conditioned responses to the CSs were tested to evaluate the fear expression. All of the participants included in the final analysis showed successful levels of fear conditioning and extinction. During the recall test, the fear responses were significantly higher in the SWS-Tone group than that in the SWS-No Tone group or the SWS-CtrT group, while the Wake-Tone group exhibited more attenuated fear responses than either the Wake-No Tone group or Wake-CtrT group. Otherwise, re-exposure to auditory tones during SWS did not affect sleep profiles. These results suggest that distinct conditions during which re-exposure to an extinction memory associated contextual cue contributes to differential effects on

  17. Neuropsychological impairment in early-onset hydrocephalus and epilepsy with continuous spike-waves during slow-wave sleep: A case report and literature review

    PubMed Central

    Posar, Annio; Parmeggiani, Antonia

    2013-01-01

    Epilepsy with continuous spike-waves during slow-wave sleep (CSWS) is often characterized by a severe cognitive and behavioral impairment. Symptomatic cases also include patients with an early-onset hydrocephalus, but in literature detailed neuropsychological data on these subjects are not available. We describe the results of serial cognitive assessments in a girl with shunted early-onset hydrocephalus, followed by partial epilepsy complicated with CSWS at 4 years 10 months, in which a dramatic cognitive and behavioral deterioration occurred few months after CSWS onset. Adrenocorticotropic hormone treatment improved both clinical and electroencephalogram picture, but an impairment of visual perception, visual-motor coordination and executive functions persisted after CSWS disappearance. We hypothesize, in this case, an involvement of right occipital-parietal lobe and prefrontal lobe. PMID:24082936

  18. Learning-dependent, transient increase of activity in noradrenergic neurons of locus coeruleus during slow wave sleep in the rat: brain stem-cortex interplay for memory consolidation?

    PubMed

    Eschenko, Oxana; Sara, Susan J

    2008-11-01

    Memory consolidation during sleep is regaining attention due to a wave of recent reports of memory improvements after sleep or deficits after sleep disturbance. Neuromodulators have been proposed as possible players in this putative off-line memory processing, without much experimental evidence. We recorded neuronal activity in the rat noradrenergic nucleus locus coeruleus (LC) using chronically implanted movable microelectrodes while monitoring the behavioral state via electrocorticogram and online video recording. Extracellular recordings of physiologically identified noradrenergic neurons of LC were made in freely behaving rats for 3 h before and after olfactory discrimination learning. On subsequent days, if LC recording remained stable, additional learning sessions were made within the olfactory discrimination protocol, including extinction, reversals, learning new odors. Contrary to the long-standing dogma about the quiescence of noradrenergic neurons of LC, we found a transient increase in LC activity in trained rats during slow wave sleep (SWS) 2 h after learning. The discovery of learning-dependent engagement of LC neurons during SWS encourages exploration of brain stem-cortical interaction during this delayed phase of memory consolidation and should bring new insights into mechanisms underlying memory formation. PMID:18321875

  19. Slow frictional waves

    NASA Astrophysics Data System (ADS)

    Viswanathan, Koushik; Sundaram, Narayan; Chandrasekar, Srinivasan

    Stick-slip, manifest as intermittent tangential motion between two dry solid surfaces, is a friction instability that governs diverse phenomena from automobile brake squeals to earthquakes. We show, using high-speed in situ imaging of an adhesive polymer interface, that low velocity stick-slip is fundamentally of three kinds, corresponding to passage of three different surface waves -- separation pulses, slip pulses and the well-known Schallamach waves. These waves, traveling much slower than elastic waves, have clear distinguishing properties. Separation pulses and Schallamach waves involve local interface separation, and propagate in opposite directions while slip pulses are characterized by a sharp stress front and do not display any interface detachment. A change in the stick-slip mode from separation to slip pulse is effected simply by increasing the normal force. Together, these three waves constitute all possible stick-slip modes in adhesive friction and are shown to have direct analogues in muscular locomotory waves in soft bodied invertebrates. A theory for slow wave propagation is also presented which is capable of explaining the attendant interface displacements, velocities and stresses.

  20. Randomised clinical trial of the effects of prolonged-release melatonin, temazepam and zolpidem on slow-wave activity during sleep in healthy people.

    PubMed

    Arbon, Emma L; Knurowska, Malgorzata; Dijk, Derk-Jan

    2015-07-01

    Current pharmacological treatments for insomnia include benzodiazepine and non-benzodiazepine hypnotics targeting γ-aminobutyric acid (GABA)A receptors, as well as agonists of the melatonin receptors MT1 and MT2. Melatonin, temazepam and zolpidem are thought to exert their effect through different mechanisms of action, but whether this leads to differential effects on electroencephalogram (EEG) power spectra during sleep in middle-aged people is currently not known. To establish whether the effects of prolonged-release melatonin (2 mg) on the nocturnal sleep EEG are different to those of temazepam (20 mg) and zolpidem (10 mg). Sixteen healthy men and women aged 55-64 years participated in a double-blind, placebo-controlled, four-way cross-over trial. Nocturnal sleep was assessed with polysomnography and spectral analysis of the EEG. The effects of single oral doses of prolonged-release melatonin, temazepam and zolpidem on EEG slow-wave activity (SWA, 0.75-4.5 Hz) and other frequencies during nocturnal non-rapid eye movement (NREM) sleep were compared. In an entire night analysis prolonged-release melatonin did not affect SWA, whereas temazepam and zolpidem significantly reduced SWA compared with placebo. Temazepam significantly reduced SWA compared with prolonged-release melatonin. Prolonged-release melatonin only reduced SWA during the first third of the night compared with placebo. These data show that the effects of prolonged-release melatonin on the nocturnal sleep EEG are minor and are different from those of temazepam and zolpidem; this is likely due to the different mechanisms of action of the medications. PMID:25922426

  1. Oscillating square wave Transcranial Direct Current Stimulation (tDCS) delivered during slow wave sleep does not improve declarative memory more than sham: A randomized sham controlled crossover study

    PubMed Central

    Sahlem, Gregory L.; Badran, Bashar W.; Halford, Jonathan J.; Williams, Nolan R.; Korte, Jeffrey E.; Leslie, Kimberly; Strachan, Martha; Breedlove, Jesse L.; Runion, Jennifer; Bachman, David L.; Uhde, Thomas W.; Borckardt, Jeffery J.; George, Mark S.

    2015-01-01

    Background A 2006 trial in healthy medical students found that anodal slow oscillating tDCS delivered bi-frontally during slow wave sleep had an enhancing effect in declarative, but not procedural memory. Although there have been supporting animal studies, and similar findings in pathological groups, this study has not been replicated, or refuted, in the intervening years. We therefore tested these earlier results for replication using similar methods with the exception of current wave form (square in our study, nearly sinusoidal in the original). Objective/Hypothesis Our objective was to test the findings of a 2006 trial suggesting bi-frontal anodal tDCS during slow wave sleep enhances declarative memory. Methods Twelve students (mean age 25, 9 women) free of medical problems underwent two testing conditions (active, sham) in a randomized counterbalanced fashion. Active stimulation consisted of oscillating square wave tDCS delivered during early Non-Rapid Eye Movement (NREM) sleep. The sham condition consisted of setting-up the tDCS device and electrodes, but not turning it on during sleep. tDCS was delivered bi-frontally with anodes placed at F3/F4, and cathodes placed at mastoids. Current density was 0.517mA/CM2, and oscillated between zero and maximal current at a frequency of 0.75Hz. Stimulation occurred during five-five minute blocks with one-minute inter-block intervals (25 minutes total stimulation). The primary outcomes were both declarative memory consolidation measured by a paired word association test (PWA), and non-declarative memory, measured by a non-dominant finger-tapping test (FTT). We also recorded and analyzed sleep EEG. Results There was no difference in the number of paired word associations remembered before compared to after sleep [(active = 3.1±3.0SD more associations) (sham = 3.8±3.1S.D more associations)]. Finger tapping improved, (non-significantly) following active stimulation [(3.6±2.7 S.D. correctly typed sequences) compared to

  2. EEG Bands of Wakeful Rest, Slow-Wave and Rapid-Eye-Movement Sleep at Different Brain Areas in Rats.

    PubMed

    Jing, Wei; Wang, Yanran; Fang, Guangzhan; Chen, Mingming; Xue, Miaomiao; Guo, Daqing; Yao, Dezhong; Xia, Yang

    2016-01-01

    Accumulating evidence reveals that neuronal oscillations with various frequency bands in the brain have different physiological functions. However, the frequency band divisions in rats were typically based on empirical spectral distribution from limited channels information. In the present study, functionally relevant frequency bands across vigilance states and brain regions were identified using factor analysis based on 9 channels EEG signals recorded from multiple brain areas in rats. We found that frequency band divisions varied both across vigilance states and brain regions. In particular, theta oscillations during REM sleep were subdivided into two bands, 5-7 and 8-11 Hz corresponding to the tonic and phasic stages, respectively. The spindle activities of SWS were different along the anterior-posterior axis, lower oscillations (~16 Hz) in frontal regions and higher in parietal (~21 Hz). The delta and theta activities co-varied in the visual and auditory cortex during wakeful rest. In addition, power spectra of beta oscillations were significantly decreased in association cortex during REM sleep compared with wakeful rest. These results provide us some new insights into understand the brain oscillations across vigilance states, and also indicate that the spatial factor should not be ignored when considering the frequency band divisions in rats. PMID:27536231

  3. EEG Bands of Wakeful Rest, Slow-Wave and Rapid-Eye-Movement Sleep at Different Brain Areas in Rats

    PubMed Central

    Jing, Wei; Wang, Yanran; Fang, Guangzhan; Chen, Mingming; Xue, Miaomiao; Guo, Daqing; Yao, Dezhong; Xia, Yang

    2016-01-01

    Accumulating evidence reveals that neuronal oscillations with various frequency bands in the brain have different physiological functions. However, the frequency band divisions in rats were typically based on empirical spectral distribution from limited channels information. In the present study, functionally relevant frequency bands across vigilance states and brain regions were identified using factor analysis based on 9 channels EEG signals recorded from multiple brain areas in rats. We found that frequency band divisions varied both across vigilance states and brain regions. In particular, theta oscillations during REM sleep were subdivided into two bands, 5–7 and 8–11 Hz corresponding to the tonic and phasic stages, respectively. The spindle activities of SWS were different along the anterior-posterior axis, lower oscillations (~16 Hz) in frontal regions and higher in parietal (~21 Hz). The delta and theta activities co-varied in the visual and auditory cortex during wakeful rest. In addition, power spectra of beta oscillations were significantly decreased in association cortex during REM sleep compared with wakeful rest. These results provide us some new insights into understand the brain oscillations across vigilance states, and also indicate that the spatial factor should not be ignored when considering the frequency band divisions in rats. PMID:27536231

  4. Spindle activity phase-locked to sleep slow oscillations.

    PubMed

    Klinzing, Jens G; Mölle, Matthias; Weber, Frederik; Supp, Gernot; Hipp, Jörg F; Engel, Andreas K; Born, Jan

    2016-07-01

    The <1Hz slow oscillation (SO) and spindles are hallmarks of mammalian non-rapid eye movement and slow wave sleep. Spindle activity occurring phase-locked to the SO is considered a candidate mediator of memory consolidation during sleep. We used source localization of magnetoencephalographic (MEG) and electroencephalographic (EEG) recordings from 11 sleeping human subjects for an in-depth analysis of the temporal and spatial properties of sleep spindles co-occurring with SOs. Slow oscillations and spindles were identified in the EEG and related to the MEG signal, providing enhanced spatial resolution. In the temporal domain, we confirmed a phase-locking of classical 12-15Hz fast spindle activity to the depolarizing SO up-state and of 9-12Hz slow spindle activity to the up-to-down-state transition of the SO. In the spatial domain, we show a broad spread of spindle activity, with less distinct anterior-posterior separation of fast and slow spindles than commonly seen in the EEG. We further tested a prediction of current memory consolidation models, namely the existence of a spatial bias of SOs over sleep spindles as a mechanism to promote localized neuronal synchronization and plasticity. In contrast to that prediction, a comparison of SOs dominating over the left vs. right hemisphere did not reveal any signs of a concurrent lateralization of spindle activity co-occurring with these SOs. Our data are consistent with the concept of the neocortical SO exerting top-down control over thalamic spindle generation. However, they call into question the notion that SOs locally coordinate spindles and thereby inform spindle-related memory processing. PMID:27103135

  5. Slow oscillating transcranial direct current stimulation during sleep has a sleep-stabilizing effect in chronic insomnia: a pilot study.

    PubMed

    Saebipour, Mohammad R; Joghataei, Mohammad T; Yoonessi, Ali; Sadeghniiat-Haghighi, Khosro; Khalighinejad, Nima; Khademi, Soroush

    2015-10-01

    Recent evidence suggests that lack of slow-wave activity may play a fundamental role in the pathogenesis of insomnia. Pharmacological approaches and brain stimulation techniques have recently offered solutions for increasing slow-wave activity during sleep. We used slow (0.75 Hz) oscillatory transcranial direct current stimulation during stage 2 of non-rapid eye movement sleeping insomnia patients for resonating their brain waves to the frequency of sleep slow-wave. Six patients diagnosed with either sleep maintenance or non-restorative sleep insomnia entered the study. After 1 night of adaptation and 1 night of baseline polysomnography, patients randomly received sham or real stimulation on the third and fourth night of the experiment. Our preliminary results show that after termination of stimulations (sham or real), slow oscillatory transcranial direct current stimulation increased the duration of stage 3 of non-rapid eye movement sleep by 33 ± 26 min (P = 0.026), and decreased stage 1 of non-rapid eye movement sleep duration by 22 ± 17.7 min (P = 0.028), compared with sham. Slow oscillatory transcranial direct current stimulation decreased stage 1 of non-rapid eye movement sleep and wake time after sleep-onset durations, together, by 55.4 ± 51 min (P = 0.045). Slow oscillatory transcranial direct current stimulation also increased sleep efficiency by 9 ± 7% (P = 0.026), and probability of transition from stage 2 to stage 3 of non-rapid eye movement sleep by 20 ± 17.8% (P = 0.04). Meanwhile, slow oscillatory transcranial direct current stimulation decreased transitions from stage 2 of non-rapid eye movement sleep to wake by 12 ± 6.7% (P = 0.007). Our preliminary results suggest a sleep-stabilizing role for the intervention, which may mimic the effect of sleep slow-wave-enhancing drugs. PMID:26014344

  6. Memory improvement via slow-oscillatory stimulation during sleep in older adults.

    PubMed

    Westerberg, Carmen E; Florczak, Susan M; Weintraub, Sandra; Mesulam, M-Marsel; Marshall, Lisa; Zee, Phyllis C; Paller, Ken A

    2015-09-01

    We examined the intriguing but controversial idea that disrupted sleep-dependent consolidation contributes to age-related memory decline. Slow-wave activity during sleep may help strengthen neural connections and provide memories with long-term stability, in which case decreased slow-wave activity in older adults could contribute to their weaker memories. One prediction from this account is that age-related memory deficits should be reduced by artificially enhancing slow-wave activity. In young adults, applying transcranial current oscillating at a slow frequency (0.75 Hz) during sleep improves memory. Here, we tested whether this procedure can improve memory in older adults. In 2 sessions separated by 1 week, we applied either slow-oscillatory stimulation or sham stimulation during an afternoon nap in a double-blind, crossover design. Memory tests were administered before and after sleep. A larger improvement in word-pair recall and higher slow-wave activity was observed with slow-oscillatory stimulation than with sham stimulation. This is the first demonstration that this procedure can improve memory in older adults, suggesting that declarative memory performance in older adults is partly dependent on slow-wave activity during sleep. PMID:26116933

  7. FEL on slow cyclotron wave

    SciTech Connect

    Silivra, A.

    1995-12-31

    A physical mechanism of interaction of fast electromagnetic wave with slow cyclotron wave of relativistic electron beam in a FEL with helical wiggler field is described. It is shown that: (1) interaction is possible for both group of steady state electron trajectories (2) positive gain is achieved within certain interval of guide field strength (3) operation wavelength for group 1 trajectories ({Omega}{sub 0}/{gamma} < k{omega}{upsilon}{parallel}) is shorter than for the conventional FEL synchronism. A nonlinear analysis shows that efficiency of slow cyclotron FEL is restricted mainly by a breakdown of a single electron synchronism due to dependence of (modified) electron cyclotron frequency on an energy of electron. Nevertheless, as numerical simulation shows, typical efficiency of 15 % order is achieved in millimeter wavelength band for the midrelativistic ({gamma}= 3 {divided_by} 4) slow cyclotron wave FEL. Tapering of magnetic field results in a substantial increase of efficiency.

  8. Recovery after prolonged sleep deprivation: residual effects of slow-release caffeine on recovery sleep, sleepiness and cognitive functions.

    PubMed

    Beaumont, Maurice; Batéjat, Denise; Coste, Olivier; Doireau, Philippe; Chauffard, Françoise; Enslen, Marc; Lagarde, Didier; Pierard, Christophe

    2005-01-01

    A long work schedule often results in sleep deprivation, sleepiness, impaired performance and fatigue. We investigated the residual effects of slow-release caffeine (SRC) on sleep, sleepiness and cognitive performance during a 42-hour recovery period following a 64-hour continuous wakefulness period in 16 healthy males, according to a double-blind, randomised, placebo-controlled, crossover study. Three hundred milligrams of SRC or placebo was given twice a day at 21:00 and 9:00 during the first 48 h of wakefulness. Recovery sleep was analysed with electroencephalography (EEG) and wrist actigraphy, daytime sleepiness with continuous EEG, sleep latency tests and actigraphy and cognitive functions with computerized tests from the NATO AGARD STRES battery. Both drug groups exhibited almost the same sleep architecture with a rebound of slow-wave sleep during both recovery nights and of REM sleep during the second night. Wakefulness level and cognitive functions were similarly impaired in both groups on the first day of recovery and partially returned to baseline on the second. To conclude, SRC appears to have no unwanted side-effects on recovery sleep, wakefulness and cognitive performance after a long period of sleep deprivation and might therefore be a useful choice over other psychostimulants for a long work schedule. PMID:15627809

  9. Slow waves in mutually inhibitory neuronal networks

    NASA Astrophysics Data System (ADS)

    Jalics, Jozsi

    2004-05-01

    A variety of experimental and modeling studies have been performed to investigate wave propagation in networks of thalamic neurons and their relationship to spindle sleep rhythms. It is believed that spindle oscillations result from the reciprocal interaction between thalamocortical (TC) and thalamic reticular (RE) neurons. We consider a network of TC and RE cells reduced to a one-layer network model and represented by a system of singularly perturbed integral-differential equations. Geometric singular perturbation methods are used to prove the existence of a locally unique slow wave pulse that propagates along the network. By seeking a slow pulse solution, we reformulate the problem to finding a heteroclinic orbit in a 3D system of ODEs with two additional constraints on the location of the orbit at two distinct points in time. In proving the persistence of the singular heteroclinic orbit, difficulties arising from the solution passing near points where normal hyperbolicity is lost on a 2D critical manifold are overcome by employing results by Wechselberger [Singularly perturbed folds and canards in R3, Thesis, TU-Wien, 1998].

  10. Slow oscillations during sleep coordinate interregional communication in cortical networks.

    PubMed

    Cox, Roy; van Driel, Joram; de Boer, Marieke; Talamini, Lucia M

    2014-12-10

    Large-amplitude sleep slow oscillations group faster neuronal oscillations and are of functional relevance for memory performance. However, relatively little is known about the impact of slow oscillations on functionally coupled networks. Here, we provide a comprehensive view on how human slow oscillatory dynamics influence various measures of brain processing. We demonstrate that slow oscillations coordinate interregional cortical communication, as assessed by phase synchrony in the sleep spindle frequency range and cross-frequency coupling between spindle and beta activity. Furthermore, we show that the organizing role of slow oscillations is restricted to circumscribed topographical areas. These findings add importantly to our basic understanding of the orchestrating role of slow oscillations. In addition, they are of considerable relevance for accounts of sleep-dependent memory reprocessing and consolidation. PMID:25505340

  11. Laminar analysis of slow wave activity in humans

    PubMed Central

    Csercsa, Richárd; Dombovári, Balázs; Fabó, Dániel; Wittner, Lucia; Erőss, Loránd; Entz, László; Sólyom, András; Rásonyi, György; Szűcs, Anna; Kelemen, Anna; Jakus, Rita; Juhos, Vera; Grand, László; Magony, Andor; Halász, Péter; Freund, Tamás F.; Maglóczky, Zsófia; Cash, Sydney S.; Papp, László; Karmos, György; Halgren, Eric

    2010-01-01

    Brain electrical activity is largely composed of oscillations at characteristic frequencies. These rhythms are hierarchically organized and are thought to perform important pathological and physiological functions. The slow wave is a fundamental cortical rhythm that emerges in deep non-rapid eye movement sleep. In animals, the slow wave modulates delta, theta, spindle, alpha, beta, gamma and ripple oscillations, thus orchestrating brain electrical rhythms in sleep. While slow wave activity can enhance epileptic manifestations, it is also thought to underlie essential restorative processes and facilitate the consolidation of declarative memories. Animal studies show that slow wave activity is composed of rhythmically recurring phases of widespread, increased cortical cellular and synaptic activity, referred to as active- or up-state, followed by cellular and synaptic inactivation, referred to as silent- or down-state. However, its neural mechanisms in humans are poorly understood, since the traditional intracellular techniques used in animals are inappropriate for investigating the cellular and synaptic/transmembrane events in humans. To elucidate the intracortical neuronal mechanisms of slow wave activity in humans, novel, laminar multichannel microelectrodes were chronically implanted into the cortex of patients with drug-resistant focal epilepsy undergoing cortical mapping for seizure focus localization. Intracortical laminar local field potential gradient, multiple-unit and single-unit activities were recorded during slow wave sleep, related to simultaneous electrocorticography, and analysed with current source density and spectral methods. We found that slow wave activity in humans reflects a rhythmic oscillation between widespread cortical activation and silence. Cortical activation was demonstrated as increased wideband (0.3–200 Hz) spectral power including virtually all bands of cortical oscillations, increased multiple- and single-unit activity and

  12. Laminar analysis of slow wave activity in humans.

    PubMed

    Csercsa, Richárd; Dombovári, Balázs; Fabó, Dániel; Wittner, Lucia; Eross, Loránd; Entz, László; Sólyom, András; Rásonyi, György; Szucs, Anna; Kelemen, Anna; Jakus, Rita; Juhos, Vera; Grand, László; Magony, Andor; Halász, Péter; Freund, Tamás F; Maglóczky, Zsófia; Cash, Sydney S; Papp, László; Karmos, György; Halgren, Eric; Ulbert, István

    2010-09-01

    Brain electrical activity is largely composed of oscillations at characteristic frequencies. These rhythms are hierarchically organized and are thought to perform important pathological and physiological functions. The slow wave is a fundamental cortical rhythm that emerges in deep non-rapid eye movement sleep. In animals, the slow wave modulates delta, theta, spindle, alpha, beta, gamma and ripple oscillations, thus orchestrating brain electrical rhythms in sleep. While slow wave activity can enhance epileptic manifestations, it is also thought to underlie essential restorative processes and facilitate the consolidation of declarative memories. Animal studies show that slow wave activity is composed of rhythmically recurring phases of widespread, increased cortical cellular and synaptic activity, referred to as active- or up-state, followed by cellular and synaptic inactivation, referred to as silent- or down-state. However, its neural mechanisms in humans are poorly understood, since the traditional intracellular techniques used in animals are inappropriate for investigating the cellular and synaptic/transmembrane events in humans. To elucidate the intracortical neuronal mechanisms of slow wave activity in humans, novel, laminar multichannel microelectrodes were chronically implanted into the cortex of patients with drug-resistant focal epilepsy undergoing cortical mapping for seizure focus localization. Intracortical laminar local field potential gradient, multiple-unit and single-unit activities were recorded during slow wave sleep, related to simultaneous electrocorticography, and analysed with current source density and spectral methods. We found that slow wave activity in humans reflects a rhythmic oscillation between widespread cortical activation and silence. Cortical activation was demonstrated as increased wideband (0.3-200 Hz) spectral power including virtually all bands of cortical oscillations, increased multiple- and single-unit activity and powerful

  13. Slow sleep spindle and procedural memory consolidation in patients with major depressive disorder

    PubMed Central

    Nishida, Masaki; Nakashima, Yusaku; Nishikawa, Toru

    2016-01-01

    Introduction Evidence has accumulated, which indicates that, in healthy individuals, sleep enhances procedural memory consolidation, and that sleep spindle activity modulates this process. However, whether sleep-dependent procedural memory consolidation occurs in patients medicated for major depressive disorder remains unclear, as are the pharmacological and physiological mechanisms that underlie this process. Methods Healthy control participants (n=17) and patients medicated for major depressive disorder (n=11) were recruited and subjected to a finger-tapping motor sequence test (MST; nondominant hand) paradigm to compare the averaged scores of different learning phases (presleep, postsleep, and overnight improvement). Participants’ brain activity was recorded during sleep with 16 electroencephalography channels (between MSTs). Sleep scoring and frequency analyses were performed on the electroencephalography data. Additionally, we evaluated sleep spindle activity, which divided the spindles into fast-frequency spindle activity (12.5–16 Hz) and slow-frequency spindle activity (10.5–12.5 Hz). Result Sleep-dependent motor memory consolidation in patients with depression was impaired in comparison with that in control participants. In patients with depression, age correlated negatively with overnight improvement. The duration of slow-wave sleep correlated with the magnitude of motor memory consolidation in patients with depression, but not in healthy controls. Slow-frequency spindle activity was associated with reduction in the magnitude of motor memory consolidation in both groups. Conclusion Because the changes in slow-frequency spindle activity affected the thalamocortical network dysfunction in patients medicated for depression, dysregulated spindle generation may impair sleep-dependent memory consolidation. Our findings may help to elucidate the cognitive deficits that occur in patients with major depression both in the waking state and during sleep. PMID

  14. Phase of Spontaneous Slow Oscillations during Sleep Influences Memory-Related Processing of Auditory Cues

    PubMed Central

    Creery, Jessica D.; Paller, Ken A.

    2016-01-01

    Slow oscillations during slow-wave sleep (SWS) may facilitate memory consolidation by regulating interactions between hippocampal and cortical networks. Slow oscillations appear as high-amplitude, synchronized EEG activity, corresponding to upstates of neuronal depolarization and downstates of hyperpolarization. Memory reactivations occur spontaneously during SWS, and can also be induced by presenting learning-related cues associated with a prior learning episode during sleep. This technique, targeted memory reactivation (TMR), selectively enhances memory consolidation. Given that memory reactivation is thought to occur preferentially during the slow-oscillation upstate, we hypothesized that TMR stimulation effects would depend on the phase of the slow oscillation. Participants learned arbitrary spatial locations for objects that were each paired with a characteristic sound (eg, cat–meow). Then, during SWS periods of an afternoon nap, one-half of the sounds were presented at low intensity. When object location memory was subsequently tested, recall accuracy was significantly better for those objects cued during sleep. We report here for the first time that this memory benefit was predicted by slow-wave phase at the time of stimulation. For cued objects, location memories were categorized according to amount of forgetting from pre- to post-nap. Conditions of high versus low forgetting corresponded to stimulation timing at different slow-oscillation phases, suggesting that learning-related stimuli were more likely to be processed and trigger memory reactivation when they occurred at the optimal phase of a slow oscillation. These findings provide insight into mechanisms of memory reactivation during sleep, supporting the idea that reactivation is most likely during cortical upstates. SIGNIFICANCE STATEMENT Slow-wave sleep (SWS) is characterized by synchronized neural activity alternating between active upstates and quiet downstates. The slow-oscillation upstates are

  15. Slow spontaneous hemodynamic oscillations during sleep measured with near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Virtanen, Jaakko; Näsi, Tiina; Noponen, Tommi; Toppila, Jussi; Salmi, Tapani; Ilmoniemi, Risto J.

    2011-07-01

    Spontaneous cerebral hemodynamic oscillations below 100 mHz reflect the level of cerebral activity, modulate hemodynamic responses to tasks and stimuli, and may aid in detecting various pathologies of the brain. Near-infrared spectroscopy (NIRS) is ideally suited for both measuring spontaneous hemodynamic oscillations and monitoring sleep, but little research has been performed to combine these two applications. We analyzed 30 all-night NIRS-electroencephalography (EEG) sleep recordings to investigate spontaneous hemodynamic activity relative to sleep stages determined by polysomnography. Signal power of hemodynamic oscillations in the low-frequency (LF, 40-150 mHz) and very-low-frequency (VLF, 3-40 mHz) bands decreased in slow-wave sleep (SWS) compared to light sleep (LS) and rapid-eye-movement (REM) sleep. No statistically significant (p < 0.05) differences in oscillation power between LS and REM were observed. However, the period of VLF oscillations around 8 mHz increased in REM sleep in line with earlier studies with other modalities. These results increase our knowledge of the physiology of sleep, complement EEG data, and demonstrate the applicability of NIRS to studying spontaneous hemodynamic fluctuations during sleep.

  16. Increased Alpha (8-12 Hz) Activity during Slow Wave Sleep as a Marker for the Transition from Implicit Knowledge to Explicit Insight

    ERIC Educational Resources Information Center

    Yordanova, Juliana; Kolev, Vasil; Wagner, Ullrich; Born, Jan; Verleger, Rolf

    2012-01-01

    The number reduction task (NRT) allows us to study the transition from implicit knowledge of hidden task regularities to explicit insight into these regularities. To identify sleep-associated neurophysiological indicators of this restructuring of knowledge representations, we measured frequency-specific power of EEG while participants slept during…

  17. Slow brain oscillations of sleep, resting state, and vigilance.

    PubMed

    Van Someren, E J W; Van Der Werf, Y D; Roelfsema, P R; Mansvelder, H D; da Silva, F H Lopes

    2011-01-01

    The most important quest of cognitive neuroscience may be to unravel the mechanisms by which the brain selects, links, consolidates, and integrates new information into its neuronal network, while preventing saturation to occur. During the past decade, neuroscientists working within several disciplines have observed an important involvement of the specific types of brain oscillations that occur during sleep--the cortical slow oscillations; during the resting state--the fMRI resting state networks including the default-mode network (DMN); and during task performance--the performance modulations that link as well to modulations in electroencephalography or magnetoencephalography frequency content. Understanding the role of these slow oscillations thus appears to be essential for our fundamental understanding of brain function. Brain activity is characterized by oscillations occurring in spike frequency, field potentials or blood oxygen level-dependent functional magnetic resonance imaging signals. Environmental stimuli, reaching the brain through our senses, activate or inactivate neuronal populations and modulate ongoing activity. The effect they sort is to a large extent determined by the momentary state of the slow endogenous oscillations of the brain. In the absence of sensory input, as is the case during rest or sleep, brain activity does not cease. Rather, its oscillations continue and change with respect to their dominant frequencies and coupling topography. This chapter briefly introduces the topics that will be addressed in this dedicated volume of Progress in Brain Research on slow oscillations and sets the stage for excellent papers discussing their molecular, cellular, network physiological and cognitive performance aspects. Getting to know about slow oscillations is essential for our understanding of plasticity, memory, brain structure from synapse to DMN, cognition, consciousness, and ultimately for our understanding of the mechanisms and functions of

  18. Napping to renew learning capacity: enhanced encoding after stimulation of sleep slow oscillations.

    PubMed

    Antonenko, Daria; Diekelmann, Susanne; Olsen, Cathrin; Born, Jan; Mölle, Matthias

    2013-04-01

    As well as consolidating memory, sleep has been proposed to serve a second important function for memory, i.e. to free capacities for the learning of new information during succeeding wakefulness. The slow wave activity (SWA) that is a hallmark of slow wave sleep could be involved in both functions. Here, we aimed to demonstrate a causative role for SWA in enhancing the capacity for encoding of information during subsequent wakefulness, using transcranial slow oscillation stimulation (tSOS) oscillating at 0.75 Hz to induce SWA in healthy humans during an afternoon nap. Encoding following the nap was tested for hippocampus-dependent declarative materials (pictures, word pairs, and word lists) and procedural skills (finger sequence tapping). As compared with a sham stimulation control condition, tSOS during the nap enhanced SWA and significantly improved subsequent encoding on all three declarative tasks (picture recognition, cued recall of word pairs, and free recall of word lists), whereas procedural finger sequence tapping skill was not affected. Our results indicate that sleep SWA enhances the capacity for encoding of declarative materials, possibly by down-scaling hippocampal synaptic networks that were potentiated towards saturation during the preceding period of wakefulness. PMID:23301831

  19. REM sleep behaviour disorder is associated with lower fast and higher slow sleep spindle densities.

    PubMed

    O'Reilly, Christian; Godin, Isabelle; Montplaisir, Jacques; Nielsen, Tore

    2015-12-01

    To investigate differences in sleep spindle properties and scalp topography between patients with rapid eye movement sleep behaviour disorder (RBD) and healthy controls, whole-night polysomnograms of 35 patients diagnosed with RBD and 35 healthy control subjects matched for age and sex were compared. Recordings included a 19-lead 10-20 electroencephalogram montage and standard electromyogram, electrooculogram, electrocardiogram and respiratory leads. Sleep spindles were automatically detected using a standard algorithm, and their characteristics (amplitude, duration, density, frequency and frequency slope) compared between groups. Topological analyses of group-discriminative features were conducted. Sleep spindles occurred at a significantly (e.g. t34 = -4.49; P = 0.00008 for C3) lower density (spindles ∙ min(-1) ) for RBD (mean ± SD: 1.61 ± 0.56 for C3) than for control (2.19 ± 0.61 for C3) participants. However, when distinguishing slow and fast spindles using thresholds individually adapted to the electroencephalogram spectrum of each participant, densities smaller (31-96%) for fast but larger (20-120%) for slow spindles were observed in RBD in all derivations. Maximal differences were in more posterior regions for slow spindles, but over the entire scalp for fast spindles. Results suggest that the density of sleep spindles is altered in patients with RBD and should therefore be investigated as a potential marker of future neurodegeneration in these patients. PMID:26041532

  20. Dynamic Analysis of the Conditional Oscillator Underlying Slow Waves in Thalamocortical Neurons

    PubMed Central

    David, François; Crunelli, Vincenzo; Leresche, Nathalie; Lambert, Régis C.

    2016-01-01

    During non-REM sleep the EEG shows characteristics waves that are generated by the dynamic interactions between cortical and thalamic oscillators. In thalamic neurons, low-threshold T-type Ca2+ channels play a pivotal role in almost every type of neuronal oscillations, including slow (< 1 Hz) waves, sleep spindles and delta waves. The transient opening of T channels gives rise to the low threshold spikes (LTSs), and associated high frequency bursts of action potentials, that are characteristically present during sleep spindles and delta waves, whereas the persistent opening of a small fraction of T channels, (i.e., ITwindow) is responsible for the membrane potential bistability underlying sleep slow oscillations. Surprisingly thalamocortical (TC) neurons express a very high density of T channels that largely exceed the amount required to generate LTSs and therefore, to support certain, if not all, sleep oscillations. Here, to clarify the relationship between T current density and sleep oscillations, we systematically investigated the impact of the T conductance level on the intrinsic rhythmic activities generated in TC neurons, combining in vitro experiments and TC neuron simulation. Using bifurcation analysis, we provide insights into the dynamical processes taking place at the transition between slow and delta oscillations. Our results show that although stable delta oscillations can be evoked with minimal T conductance, the full range of slow oscillation patterns, including groups of delta oscillations separated by Up states (“grouped-delta slow waves”) requires a high density of T channels. Moreover, high levels of T conductance ensure the robustness of different types of slow oscillations. PMID:26941611

  1. EEG slow-wave coherence changes in propofol-induced general anesthesia: experiment and theory

    PubMed Central

    Wang, Kaier; Steyn-Ross, Moira L.; Steyn-Ross, D. A.; Wilson, Marcus T.; Sleigh, Jamie W.

    2014-01-01

    The electroencephalogram (EEG) patterns recorded during general anesthetic-induced coma are closely similar to those seen during slow-wave sleep, the deepest stage of natural sleep; both states show patterns dominated by large amplitude slow waves. Slow oscillations are believed to be important for memory consolidation during natural sleep. Tracking the emergence of slow-wave oscillations during transition to unconsciousness may help us to identify drug-induced alterations of the underlying brain state, and provide insight into the mechanisms of general anesthesia. Although cellular-based mechanisms have been proposed, the origin of the slow oscillation has not yet been unambiguously established. A recent theoretical study by Steyn-Ross et al. (2013) proposes that the slow oscillation is a network, rather than cellular phenomenon. Modeling anesthesia as a moderate reduction in gap-junction interneuronal coupling, they predict an unconscious state signposted by emergent low-frequency oscillations with chaotic dynamics in space and time. They suggest that anesthetic slow-waves arise from a competitive interaction between symmetry-breaking instabilities in space (Turing) and time (Hopf), modulated by gap-junction coupling strength. A significant prediction of their model is that EEG phase coherence will decrease as the cortex transits from Turing–Hopf balance (wake) to Hopf-dominated chaotic slow-waves (unconsciousness). Here, we investigate changes in phase coherence during induction of general anesthesia. After examining 128-channel EEG traces recorded from five volunteers undergoing propofol anesthesia, we report a significant drop in sub-delta band (0.05–1.5 Hz) slow-wave coherence between frontal, occipital, and frontal–occipital electrode pairs, with the most pronounced wake-vs.-unconscious coherence changes occurring at the frontal cortex. PMID:25400558

  2. EEG slow-wave coherence changes in propofol-induced general anesthesia: experiment and theory.

    PubMed

    Wang, Kaier; Steyn-Ross, Moira L; Steyn-Ross, D A; Wilson, Marcus T; Sleigh, Jamie W

    2014-01-01

    The electroencephalogram (EEG) patterns recorded during general anesthetic-induced coma are closely similar to those seen during slow-wave sleep, the deepest stage of natural sleep; both states show patterns dominated by large amplitude slow waves. Slow oscillations are believed to be important for memory consolidation during natural sleep. Tracking the emergence of slow-wave oscillations during transition to unconsciousness may help us to identify drug-induced alterations of the underlying brain state, and provide insight into the mechanisms of general anesthesia. Although cellular-based mechanisms have been proposed, the origin of the slow oscillation has not yet been unambiguously established. A recent theoretical study by Steyn-Ross et al. (2013) proposes that the slow oscillation is a network, rather than cellular phenomenon. Modeling anesthesia as a moderate reduction in gap-junction interneuronal coupling, they predict an unconscious state signposted by emergent low-frequency oscillations with chaotic dynamics in space and time. They suggest that anesthetic slow-waves arise from a competitive interaction between symmetry-breaking instabilities in space (Turing) and time (Hopf), modulated by gap-junction coupling strength. A significant prediction of their model is that EEG phase coherence will decrease as the cortex transits from Turing-Hopf balance (wake) to Hopf-dominated chaotic slow-waves (unconsciousness). Here, we investigate changes in phase coherence during induction of general anesthesia. After examining 128-channel EEG traces recorded from five volunteers undergoing propofol anesthesia, we report a significant drop in sub-delta band (0.05-1.5 Hz) slow-wave coherence between frontal, occipital, and frontal-occipital electrode pairs, with the most pronounced wake-vs.-unconscious coherence changes occurring at the frontal cortex. PMID:25400558

  3. Slow-wave synchronous pick-up and kicker

    SciTech Connect

    DiMassa, G.

    1988-01-01

    Slow-wave synchronous pick-up (PU) and Kicker (K) are proposed for the stochastic cooling of bunched beams in RHIC. A corrugated waveguide is used to support a slow wave that is synchronous with the beam.

  4. Slow-wave disruption enhances the accessibility of positive memory traces.

    PubMed

    Goldschmied, Jennifer R; Cheng, Philip; Kim, Hyang Sook; Casement, Melynda; Armitage, Roseanne; Deldin, Patricia J

    2015-11-01

    The purpose of this study was to explore the effects of slow-wave disruption on positive and negative word recognition in a sample of healthy control participants and those with major depressive disorder. Prior to sleep, participants learned a set of emotional and neutral words during an encoding task by responding whether or not the word described them. Following baseline sleep, participants underwent one night of selective slow-wave disruption by auditory stimuli. Accuracy and reaction time to a recognition word set, including both positive and negative words, was assessed in the morning. Repeated-measures ANOVA revealed a significant interaction between word valence and condition, with positive words recognized significantly faster than negative words after disruption, in only healthy control participants. There were no significant results in those with major depressive disorder, or with regard to accuracy. These results may add to the increasing body of literature suggesting a hedonic bias to positive stimuli following sleep disruption. PMID:26409320

  5. Sheet beam slow-wave amplifiers

    SciTech Connect

    Kirolous, H.; Joe, J.; Basten, M.A.; Booske, J.H.; Scharer, J.E.; Anderson, J.; True, R.; Scheitrum, G.

    1994-12-31

    Sheet electron beams used in conjunction with slow-wave (Cerenkov) structures are a promising way to realize higher average power millimeter-wave amplifiers. For example, a sheet beam with a meander line structure is proposed to obtain a 100 watt W-band power booster amplifier. A sheet beam with a tapered grating structure is also being considered as a wideband ({approximately} 10--20% instantaneous bandwidth) Ka-band amplifier with approximately 10 kW of average output power. The authors describe results of research that examine critical technological issues relevant to the realization of the proposed devices. The method of forming a sheet beam using magnetic quadrupole lenses and focusing it using periodically-cusped magnetic (PCM) fields are discussed. A pencil beam from a 10 kV, 0.25 A Pierce electron source is used for the initial investigations. The EGUN simulations with the measured magnetic field indicates that a thin (2 mm dia.) beam is available at the interaction region. Beam characterization has been performed using current density probes and an electrostatic velocity spread analyzer. Numerical modeling and cold test measurements of a tapered slow-wave structure together with the simulations and measurements of small-signal gain and bandwidth are also presented.

  6. Slow EIT waves as gravity modes

    SciTech Connect

    Vranjes, J.

    2011-06-15

    The EIT waves [named after the extreme-ultraviolet imaging telescope (EIT) onboard the solar and heliospheric observatory (SOHO)] are in the literature usually described as fast magneto-acoustic (FMA) modes. However, observations show that a large percentage of these events propagate with very slow speeds that may be as low as 20 km/s. This is far below the FMA wave speed which cannot be below the sound speed, the latter being typically larger than 10{sup 2} km/s in the corona. In the present study, it is shown that, to account for such low propagation speed, a different wave model should be used, based on the theory of gravity waves, both internal (IG) and surface (SG) ones. The gravity modes are physically completely different from the FMA mode, as they are essentially dispersive and in addition the IG wave is a transverse mode. Both the IG and the SG mode separately can provide proper propagation velocities in the whole low speed range.

  7. Coupling between whistler waves and slow-mode solitary waves

    SciTech Connect

    Tenerani, A.; Califano, F.; Pegoraro, F.; Le Contel, O.

    2012-05-15

    The interplay between electron- and ion-scale phenomena is of general interest for both laboratory and space plasma physics. In this paper, we investigate the linear coupling between whistler waves and slow magnetosonic solitons through two-fluid numerical simulations. Whistler waves can be trapped in the presence of inhomogeneous external fields such as a density hump or hole where they can propagate for times much longer than their characteristic time scale, as shown by laboratory experiments and space measurements. Space measurements have detected whistler waves also in correspondence to magnetic holes, i.e., to density humps with magnetic field minima extending on ion-scales. This raises the interesting question of how ion-scale structures can couple to whistler waves. Slow magnetosonic solitons share some of the main features of a magnetic hole. Using the ducting properties of an inhomogeneous plasma as a guide, we present a numerical study of whistler waves that are trapped and transported inside propagating slow magnetosonic solitons.

  8. Slow oscillating transcranial direct current stimulation during non-rapid eye movement sleep improves behavioral inhibition in attention-deficit/hyperactivity disorder

    PubMed Central

    Munz, Manuel T.; Prehn-Kristensen, Alexander; Thielking, Frederieke; Mölle, Matthias; Göder, Robert; Baving, Lioba

    2015-01-01

    Background: Behavioral inhibition, which is a later-developing executive function (EF) and anatomically located in prefrontal areas, is impaired in attention-deficit and hyperactivity disorder (ADHD). While optimal EFs have been shown to depend on efficient sleep in healthy subjects, the impact of sleep problems, frequently reported in ADHD, remains elusive. Findings of macroscopic sleep changes in ADHD are inconsistent, but there is emerging evidence for distinct microscopic changes with a focus on prefrontal cortical regions and non-rapid eye movement (non-REM) slow-wave sleep. Recently, slow oscillations (SO) during non-REM sleep were found to be less functional and, as such, may be involved in sleep-dependent memory impairments in ADHD. Objective:By augmenting slow-wave power through bilateral, slow oscillating transcranial direct current stimulation (so-tDCS, frequency = 0.75 Hz) during non-REM sleep, we aimed to improve daytime behavioral inhibition in children with ADHD. Methods: Fourteen boys (10–14 years) diagnosed with ADHD were included. In a randomized, double-blind, cross-over design, patients received so-tDCS either in the first or in the second experimental sleep night. Inhibition control was assessed with a visuomotor go/no-go task. Intrinsic alertness was assessed with a simple stimulus response task. To control for visuomotor performance, motor memory was assessed with a finger sequence tapping task. Results: SO-power was enhanced during early non-REM sleep, accompanied by slowed reaction times and decreased standard deviations of reaction times, in the go/no-go task after so-tDCS. In contrast, intrinsic alertness, and motor memory performance were not improved by so-tDCS. Conclusion: Since behavioral inhibition but not intrinsic alertness or motor memory was improved by so-tDCS, our results suggest that lateral prefrontal slow oscillations during sleep might play a specific role for executive functioning in ADHD. PMID:26321911

  9. Driving sleep slow oscillations by auditory closed-loop stimulation-a self-limiting process.

    PubMed

    Ngo, Hong-Viet V; Miedema, Arjan; Faude, Isabel; Martinetz, Thomas; Mölle, Matthias; Born, Jan

    2015-04-29

    The <1 Hz EEG slow oscillation (SO) is a hallmark of slow-wave sleep (SWS) and is critically involved in sleep-associated memory formation. Previous studies showed that SOs and associated memory function can be effectively enhanced by closed-loop auditory stimulation, when clicks are presented in synchrony with upcoming SO up states. However, increasing SOs and synchronized excitability also bear the risk of emerging seizure activity, suggesting the presence of mechanisms in the healthy brain that counter developing hypersynchronicity during SOs. Here, we aimed to test the limits of driving SOs through closed-loop auditory stimulation in healthy humans. Study I tested a "Driving stimulation" protocol (vs "Sham") in which trains of clicks were presented in synchrony with SO up states basically as long as an ongoing SO train was identified on-line. Study II compared Driving stimulation with a "2-Click" protocol where the maximum of stimuli delivered in a train was limited to two clicks. Stimulation was applied during SWS in the first 210 min of nocturnal sleep. Before and after sleep declarative word-pair memories were tested. Compared with the Sham control, Driving stimulation prolonged SO trains and enhanced SO amplitudes, phase-locked spindle activity, and overnight retention of word pairs (all ps < 0.05). Importantly, effects of Driving stimulation did not exceed those of 2-Click stimulation (p > 0.180), indicating the presence of a mechanism preventing the development of hypersynchronicity during SO activity. Assessment of temporal dynamics revealed a rapidly fading phase-locked spindle activity during repetitive click stimulation, suggesting that spindle refractoriness contributes to this protective mechanism. PMID:25926443

  10. Superconducting niobium thin film slow-wave structures

    NASA Technical Reports Server (NTRS)

    Bautista, J. J.; Petty, S. M.; Allen, L. H.; Beasley, M. R.; Hammond, R. H.

    1983-01-01

    A superconducting comb structure as a slow-wave element in a traveling-wave maser will significantly improve maser noise temperature and gain by reducing the insertion loss. The results of the insertion loss measurements of superconducting niobium slow-wave structures subjected to maser operating conditions at X-Band frequencies are presented.

  11. Review of Slow-Wave Structures

    NASA Technical Reports Server (NTRS)

    Wallett, Thomas M.; Qureshi, A. Haq

    1994-01-01

    The majority of recent theoretical and experimental reports published in the literature dealing with helical slow-wave structures focus on the dispersion characteristics and their effects due to the finite helix wire thickness and attenuation, dielectric loading, metal loading, and the introduction of plasma. In many papers, an effective dielectric constant is used to take into account helix wire dimensions and conductivity losses, while the propagation constant of the signal and the interaction impedance of the structure are found to depend on the surface resistivity of the helix. Also, various dielectric supporting rods are simulated by one or several uniform cylinders having an effective dielectric constant, while metal vane loading and plasma effects are incorporated in the effective dielectric constant. The papers dealing with coupled cavities and folded or loaded wave guides describe equivalent circuit models, efficiency enhancement, and the prediction of instabilities for these structures. Equivalent circuit models of various structures are found using computer software programs SUPERFISH and TOUCHSTONE. Efficiency enhancement in tubes is achieved through dynamic velocity and phase adjusted tapers using computer techniques. The stability threshold of unwanted antisymmetric and higher order modes is predicted using SOS and MAGIC codes and the dependence of higher order modes on beam conductance, section length, and effective Q of a cavity is shown.

  12. Review of slow-wave structures

    NASA Astrophysics Data System (ADS)

    Wallett, Thomas M.; Qureshi, A. Haq

    1994-06-01

    The majority of recent theoretical and experimental reports published in the literature dealing with helical slow-wave structures focus on the dispersion characteristics and their effects due to the finite helix wire thickness and attenuation, dielectric loading, metal loading, and the introduction of plasma. In many papers, an effective dielectric constant is used to take into account helix wire dimensions and conductivity losses, while the propagation constant of the signal and the interaction impedance of the structure are found to depend on the surface resistivity of the helix. Also, various dielectric supporting rods are simulated by one or several uniform cylinders having an effective dielectric constant, while metal vane loading and plasma effects are incorporated in the effective dielectric constant. The papers dealing with coupled cavities and folded or loaded wave guides describe equivalent circuit models, efficiency enhancement, and the prediction of instabilities for these structures. Equivalent circuit models of various structures are found using computer software programs SUPERFISH and TOUCHSTONE. Efficiency enhancement in tubes is achieved through dynamic velocity and phase adjusted tapers using computer techniques. The stability threshold of unwanted antisymmetric and higher order modes is predicted using SOS and MAGIC codes and the dependence of higher order modes on beam conductance, section length, and effective Q of a cavity is shown.

  13. Waves in low-beta plasmas - Slow shocks

    NASA Technical Reports Server (NTRS)

    Steinolfson, R. S.; Hundhausen, A. J.

    1989-01-01

    Results from wave theory and numerical simulation of the nonlinear MHD equations are used to study the response of a conducting fluid containing an embedded magnetic field with beta less than 1 to the sudden injection of material along the field lines. It is shown that the injection produces slow shocks with configurations which are concave toward the ejecta driver. Fast-mode waves which have not steepened into the shock precede the slow shock and alter the ambient medium. When beta equals 0.1, the fast mode becomes a transverse wave for parallel propagation, while the slow wave approaches a longitudinal, or sound, wave.

  14. Is There a Relation between EEG-Slow Waves and Memory Dysfunction in Epilepsy? A Critical Appraisal

    PubMed Central

    Höller, Yvonne; Trinka, Eugen

    2015-01-01

    Is there a relationship between peri-ictal slow waves, loss of consciousness, memory, and slow-wave sleep, in patients with different forms of epilepsy? We hypothesize that mechanisms, which result in peri-ictal slow-wave activity as detected by the electroencephalogram, could negatively affect memory processes. Slow waves (≤4 Hz) can be found in seizures with impairment of consciousness and also occur in focal seizures without impairment of consciousness but with inhibited access to memory functions. Peri-ictal slow waves are regarded as dysfunctional and are probably caused by mechanisms, which are essential to disturb the consolidation of memory entries in these patients. This is in strong contrast to physiological slow-wave activity during deep sleep, which is thought to group memory-consolidating fast oscillatory activity. In patients with epilepsy, slow waves may not only correlate with the peri-ictal clouding of consciousness, but could be the epiphenomenon of mechanisms, which interfere with normal brain function in a wider range. These mechanisms may have transient impacts on memory, such as temporary inhibition of memory systems, altered patterns of hippocampal–neocortical interactions during slow-wave sleep, or disturbed cross-frequency coupling of slow and fast oscillations. In addition, repeated tonic–clonic seizures over the years in uncontrolled chronic epilepsy may cause a progressive cognitive decline. This hypothesis can only be assessed in long-term prospective studies. These studies could disentangle the reversible short-term impacts of seizures, and the impacts of chronic uncontrolled seizures. Chronic uncontrolled seizures lead to irreversible memory impairment. By contrast, short-term impacts do not necessarily lead to a progressive cognitive decline but result in significantly impaired peri-ictal memory performance. PMID:26124717

  15. Sharp Slow Waves in the EEG.

    PubMed

    Janati, A Bruce; AlGhasab, Naif Saad; Alshammari, Raed Ayed; saad AlGhassab, Abdulmohsen; Al-Aslami Yossef Fahad

    2016-06-01

    There exists a paucity of data in the EEG literature on characteristics of "atypical" interictal epileptiform discharges (IEDs), including sharp slow waves (SSWs). This article aims to address the clinical, neurophysiological, and neuropathological significance of SSW The EEGs of 920 patients at a tertiary-care facility were prospectively reviewed over a period of one year. Thirty-six patients had SSWs in their EEG. Of these, 6 patients were excluded because of inadequate clinical data. The clinical and neuroimaging data of the remaining 30 patients were then retrospectively collected and reviewed, and the findings were correlated. The data revealed that SSWs were rare and age-related EEG events occurring primarily in the first two decades of life. All patients with SSWs had documented epilepsy, presenting clinically with partial or generalized epilepsy. It is notable that one-third of the patients with SSWs had chronic or static central nervous system (CNS) pathology, particularly congenital CNS anomalies. Though more than one mechanism may be involved in the pathogenesis of SSWs, this research indicates that the most compelling theory is a deeply seated cortical generator giving rise to this EEG pattern. The presence of SSWs should alert clinicians to the presence of partial or generalized epilepsy or an underlying chronic or static CNS pathology, in particular congenital CNS anomalies, underscoring the significance of brain magnetic resonance imaging in the work-up of this population. PMID:27373055

  16. Epileptic encephalopathy with continuous spike and wave during sleep associated to periventricular leukomalacia.

    PubMed

    De Grandis, Elisa; Mancardi, Maria Margherita; Carelli, Valentina; Carpaneto, Manuela; Morana, Giovanni; Prato, Giulia; Mirabelli-Badenier, Marisol; Pinto, Francesca; Veneselli, Edvige; Baglietto, Maria Giuseppina

    2014-11-01

    Periventricular leukomalacia is the most common type of brain injury in premature infants. Our aim is to describe the frequency and the features of epilepsy in a single-center population of 137 children with periventricular leukomalacia. Forty-two of the 137 (31%) patients presented epilepsy. Twelve percent of these patients presented West syndrome, whereas 19% showed a pattern of continuous spike-waves during slow sleep syndrome. In the latter group, outcome was frequently unfavorable, with a greater number of seizures and more drug resistance. A significant association was found between epilepsy and neonatal seizures, spastic tetraplegia, and mental retardation. Although less common than in other forms of brain injury, epilepsy is nevertheless a significant complication in children with periventricular leukomalacia. The fairly frequent association with continuous spike-waves during slow sleep syndrome deserves particular attention: electroencephalographic sleep monitoring is important in order to provide early treatment and prevent further neurologic deterioration. PMID:24293309

  17. Nonlinear slow magnetoacoustic waves in coronal plasma structures

    NASA Astrophysics Data System (ADS)

    Afanasyev, A. N.; Nakariakov, V. M.

    2015-01-01

    Context. There is abundant observational evidence of longitudinal waves in the plasma structures of the solar corona. These essentially compressive waves are confidently interpreted as slow magnetoacoustic waves. The use of the slow waves in plasma diagnostics and estimating their possible contribution to plasma heating and acceleration require detailed theoretical modelling. Aims: We investigate the role of obliqueness and magnetic effects in the evolution of slow magnetoacoustic waves, also called tube waves, in field-aligned plasma structures. Special attention is paid to the wave damping caused by nonlinear steepening. Methods: We considered an untwisted straight axisymmetric field-aligned plasma cylinder and analysed the behaviour of the slow magnetoacoustic waves that are guided by this plasma structure. We adopted a thin flux tube approximation. We took into account dissipation caused by viscosity, resistivity and thermal conduction, and nonlinearity. Effects of stratification and dispersion caused by the finite radius of the flux tube were neglected. Results: We derive the Burgers-type evolutionary equation for tube waves in a uniform plasma cylinder. Compared with a plane acoustic wave, the formation of shock fronts in tube waves is found to occur at a larger distance from the source. In addition, tube waves experience stronger damping. These effects are most pronounced in plasmas with the parameter β at about or greater than unity. In a low-β plasma, the evolution of tube waves can satisfactorily be described with the Burgers equation for plane acoustic waves. Conclusions:

  18. Slow Sleep Spindle Activity, Declarative Memory, and General Cognitive Abilities in Children

    PubMed Central

    Hoedlmoser, Kerstin; Heib, Dominik P.J.; Roell, Judith; Peigneux, Philippe; Sadeh, Avi; Gruber, Georg; Schabus, Manuel

    2014-01-01

    Study Objectives: Functional interactions between sleep spindle activity, declarative memory consolidation, and general cognitive abilities in school-aged children. Design: Healthy, prepubertal children (n = 63; mean age 9.56 ± 0.76 y); ambulatory all-night polysomnography (2 nights); investigating the effect of prior learning (word pair association task; experimental night) versus nonlearning (baseline night) on sleep spindle activity; general cognitive abilities assessed using the Wechsler Intelligence Scale for Children-IV (WISC-IV). Measurements and Results: Analysis of spindle activity during nonrapid eye movement sleep (N2 and N3) evidenced predominant peaks in the slow (11-13 Hz) but not in the fast (13-15 Hz) sleep spindle frequency range (baseline and experimental night). Analyses were restricted to slow sleep spindles. Changes in spindle activity from the baseline to the experimental night were not associated with the overnight change in the number of recalled words reflecting declarative memory consolidation. Children with higher sleep spindle activity as measured at frontal, central, parietal, and occipital sites during both baseline and experimental nights exhibited higher general cognitive abilities (WISC-IV) and declarative learning efficiency (i.e., number of recalled words before and after sleep). Conclusions: Slow sleep spindles (11-13 Hz) in children age 8–11 y are associated with inter-individual differences in general cognitive abilities and learning efficiency. Citation: Hoedlmoser K, Heib DPJ, Roell J, Peigneux P, Sadeh A, Gruber G, Schabus M. Slow sleep spindle activity, declarative memory, and general cognitive abilities in children. SLEEP 2014;37(9):1501-1512. PMID:25142558

  19. Spontaneous neuronal burst discharges as dependent and independent variables in the maturation of cerebral cortex tissue cultured in vitro: a review of activity-dependent studies in live 'model' systems for the development of intrinsically generated bioelectric slow-wave sleep patterns.

    PubMed

    Corner, Michael A

    2008-11-01

    A survey is presented of recent experiments which utilize spontaneous neuronal spike trains as dependent and/or independent variables in developing cerebral cortex cultures when synaptic transmission is interfered with for varying periods of time. Special attention is given to current difficulties in selecting suitable preparations for carrying out biologically relevant developmental studies, and in applying spike-train analysis methods with sufficient resolution to detect activity-dependent age and treatment effects. A hierarchy of synchronized nested burst discharges which approximate early slow-wave sleep patterns in the intact organism is established as a stable basis for isolated cortex function. The complexity of reported long- and short-term homeostatic responses to experimental interference with synaptic transmission is reviewed, and the crucial role played by intrinsically generated bioelectric activity in the maturation of cortical networks is emphasized. PMID:18722470

  20. Electron heating and current drive by mode converted slow waves

    SciTech Connect

    Majeski, R.; Phillips, C.K.; Wilson, J.R.

    1994-08-01

    An approach to obtaining efficient single pass mode conversion at high parallel wavenumber from the fast magnetosonic wave to the slow ion Bernstein wave, in a two ion species tokamak plasma, is described. The intent is to produce localized electron heating or current drive via the mode converted slow wave. In particular, this technique can be adapted to off-axis current drive for current profile control. Modelling for the case of deuterium-tritium plasmas in TFTR is presented.

  1. Fear extinction memory consolidation requires potentiation of pontine-wave activity during REM sleep.

    PubMed

    Datta, Subimal; O'Malley, Matthew W

    2013-03-01

    Sleep plays an important role in memory consolidation within multiple memory systems including contextual fear extinction memory, but little is known about the mechanisms that underlie this process. Here, we show that fear extinction training in rats, which extinguished conditioned fear, increased both slow-wave sleep and rapid-eye movement (REM) sleep. Surprisingly, 24 h later, during memory testing, only 57% of the fear-extinguished animals retained fear extinction memory. We found that these animals exhibited an increase in phasic pontine-wave (P-wave) activity during post-training REM sleep, which was absent in the 43% of animals that failed to retain fear extinction memory. The results of this study provide evidence that brainstem activation, specifically potentiation of phasic P-wave activity, during post-training REM sleep is critical for consolidation of fear extinction memory. The results of this study also suggest that, contrary to the popular hypothesis of sleep and memory, increased sleep after training alone does not guarantee consolidation and/or retention of fear extinction memory. Rather, the potentiation of specific sleep-dependent physiological events may be a more accurate predictor for successful consolidation of fear extinction memory. Identification of this unique mechanism will significantly improve our present understanding of the cellular and molecular mechanisms that underlie the sleep-dependent regulation of emotional memory. Additionally, this discovery may also initiate development of a new, more targeted treatment method for clinical disorders of fear and anxiety in humans that is more efficacious than existing methods such as exposure therapy that incorporate only fear extinction. PMID:23467372

  2. Fear Extinction Memory Consolidation Requires Potentiation of Pontine-Wave Activity during REM Sleep

    PubMed Central

    Datta, Subimal; O'Malley, Matthew W .

    2013-01-01

    Sleep plays an important role in memory consolidation within multiple memory systems including contextual fear extinction memory, but little is known about the mechanisms that underlie this process. Here, we show that fear extinction training in rats, which extinguished conditioned fear, increased both slow-wave sleep and rapid-eye movement (REM) sleep. Surprisingly, 24 h later, during memory testing, only 57% of the fear-extinguished animals retained fear extinction memory. We found that these animals exhibited an increase in phasic pontine-wave (P-wave) activity during post-training REM sleep, which was absent in the 43% of animals that failed to retain fear extinction memory. The results of this study provide evidence that brainstem activation, specifically potentiation of phasic P-wave activity, during post-training REM sleep is critical for consolidation of fear extinction memory. The results of this study also suggest that, contrary to the popular hypothesis of sleep and memory, increased sleep after training alone does not guarantee consolidation and/or retention of fear extinction memory. Rather, the potentiation of specific sleep-dependent physiological events may be a more accurate predictor for successful consolidation of fear extinction memory. Identification of this unique mechanism will significantly improve our present understanding of the cellular and molecular mechanisms that underlie the sleep-dependent regulation of emotional memory. Additionally, this discovery may also initiate development of a new, more targeted treatment method for clinical disorders of fear and anxiety in humans that is more efficacious than existing methods such as exposure therapy that incorporate only fear extinction. PMID:23467372

  3. Slow electrostatic solitary waves in Earth's plasma sheet boundary layer

    NASA Astrophysics Data System (ADS)

    Kakad, Amar; Kakad, Bharati; Anekallu, Chandrasekhar; Lakhina, Gurbax; Omura, Yoshiharu; Fazakerley, Andrew

    2016-05-01

    We modeled Cluster spacecraft observations of slow electrostatic solitary waves (SESWs) in the Earth's northern plasma sheet boundary layer (PSBL) region on the basis of nonlinear fluid theory and fluid simulation. Various plasma parameters observed by the Cluster satellite at the time of the SESWs were examined to investigate the generation process of the SESWs. The nonlinear fluid model shows the coexistence of slow and fast ion acoustic waves and the presence of electron acoustic waves in the PSBL region. The fluid simulations, performed to examine the evolution of these waves in the PSBL region, showed the presence of an extra mode along with the waves supported by the nonlinear fluid theory. This extra mode is identified as the Buneman mode, which is generated by relative drifts of ions and electrons. A detailed investigation of the characteristics of the SESWs reveals that the SESWs are slow ion acoustic solitary waves.

  4. Hippocampal sharp-wave ripples in waking and sleeping states.

    PubMed

    Roumis, Demetris K; Frank, Loren M

    2015-12-01

    Waking and sleeping states are privileged periods for distinct mnemonic processes. In waking behavior, rapid retrieval of previous experience aids memory-guided decision making. In sleep, a gradual series of reactivated associations supports consolidation of episodes into memory networks. Synchronized bursts of hippocampal place cells during events called sharp-wave ripples communicate associated neural patterns across distributed circuits in both waking and sleeping states. Differences between sleep and awake sharp-wave ripples, and in particular the accuracy of recapitulated experience, highlight their state-dependent roles in memory processes. PMID:26011627

  5. Global intracellular slow-wave dynamics of the thalamocortical system.

    PubMed

    Sheroziya, Maxim; Timofeev, Igor

    2014-06-25

    It is widely accepted that corticothalamic neurons recruit the thalamus in slow oscillation, but global slow-wave thalamocortical dynamics have never been experimentally shown. We analyzed intracellular activities of neurons either from different cortical areas or from a variety of specific and nonspecific thalamic nuclei in relation to the phase of global EEG signal in ketamine-xylazine anesthetized mice. We found that, on average, slow-wave active states started off within frontal cortical areas as well as higher-order and intralaminar thalamus (posterior and parafascicular nuclei) simultaneously. Then, the leading edge of active states propagated in the anteroposterior/lateral direction over the cortex at ∼40 mm/s. The latest structure we recorded within the slow-wave cycle was the anterior thalamus, which followed active states of the retrosplenial cortex. Active states from different cortical areas tended to terminate simultaneously. Sensory thalamic ventral posterior medial and lateral geniculate nuclei followed cortical active states with major inhibitory and weak tonic-like "modulator" EPSPs. In these nuclei, sharp-rising, large-amplitude EPSPs ("drivers") were not modulated by cortical slow waves, suggesting their origin in ascending pathways. The thalamic active states in other investigated nuclei were composed of depolarization: some revealing "driver"- and "modulator"-like EPSPs, others showing "modulator"-like EPSPs only. We conclude that sensory thalamic nuclei follow the propagating cortical waves, whereas neurons from higher-order thalamic nuclei display "hub dynamics" and thus may contribute to the generation of cortical slow waves. PMID:24966387

  6. Shock Formation of Slow Magnetosonic Waves in Coronal Plumes

    NASA Technical Reports Server (NTRS)

    Cuntz, Manfred; Suess, Steven T.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    We investigate the height of shock formation in coroner plumes for slow magnetosonic waves. The models take into account plume geometric spreading, heat conduction and radiative damping. The wave parameters as well as the spreading functions of the plumes and the base magnetic field strengths are given by empirical constraints mostly from Solar and Heliospheric Observatory/Ultraviolet Coronagraph Spectrometer (SOHO/UVCS). Our models show that shock formation occurs at low coronal heights, i.e., within 1.3 solar radius, depending on the model parameters. The shock formation is calculated using the well-established wave breaking condition given by the intersection of C+ characteristics in the space-time plane. Our models show that shock heating by slow magnetosonic waves is expected to be relevant at most heights in solar coronal plumes, although slow magnetosonic waves are most likely not a solely operating energy supply mechanism.

  7. Slow Magnetosonic Waves and Fast Flows in Active Region Loops

    NASA Technical Reports Server (NTRS)

    Ofman, L.; Wang, T. J.; Davila, J. M.

    2012-01-01

    Recent extreme ultraviolet spectroscopic observations indicate that slow magnetosonic waves are present in active region (AR) loops. Some of the spectral data were also interpreted as evidence of fast (approx 100-300 km/s) quasiperiodic flows. We have performed three-dimensional magnetohydrodynamic (3D MHD) modeling of a bipolar AR that contains impulsively generated waves and flows in coronal loops. The model AR is initiated with a dipole magnetic field and gravitationally stratified density, with an upflow-driven steadily or periodically in localized regions at the footpoints of magnetic loops. The resulting flows along the magnetic field lines of the AR produce higher density loops compared to the surrounding plasma by injection of material into the flux tubes and the establishment of siphon flow.We find that the impulsive onset of flows with subsonic speeds result in the excitation of damped slow magnetosonic waves that propagate along the loops and coupled nonlinearly driven fast-mode waves. The phase speed of the slow magnetosonic waves is close to the coronal sound speed. When the amplitude of the driving pulses is increased we find that slow shock-like wave trains are produced. When the upflows are driven periodically, undamped oscillations are produced with periods determined by the periodicity of the upflows. Based on the results of the 3D MHD model we suggest that the observed slow magnetosonic waves and persistent upflows may be produced by the same impulsive events at the bases of ARs.

  8. SLOW MAGNETOSONIC WAVES AND FAST FLOWS IN ACTIVE REGION LOOPS

    SciTech Connect

    Ofman, L.; Wang, T. J.; Davila, J. M.

    2012-08-01

    Recent extreme ultraviolet spectroscopic observations indicate that slow magnetosonic waves are present in active region (AR) loops. Some of the spectral data were also interpreted as evidence of fast ({approx}100-300 km s{sup -1}) quasi-periodic flows. We have performed three-dimensional magnetohydrodynamic (3D MHD) modeling of a bipolar AR that contains impulsively generated waves and flows in coronal loops. The model AR is initiated with a dipole magnetic field and gravitationally stratified density, with an upflow-driven steadily or periodically in localized regions at the footpoints of magnetic loops. The resulting flows along the magnetic field lines of the AR produce higher density loops compared to the surrounding plasma by injection of material into the flux tubes and the establishment of siphon flow. We find that the impulsive onset of flows with subsonic speeds result in the excitation of damped slow magnetosonic waves that propagate along the loops and coupled nonlinearly driven fast-mode waves. The phase speed of the slow magnetosonic waves is close to the coronal sound speed. When the amplitude of the driving pulses is increased we find that slow shock-like wave trains are produced. When the upflows are driven periodically, undamped oscillations are produced with periods determined by the periodicity of the upflows. Based on the results of the 3D MHD model we suggest that the observed slow magnetosonic waves and persistent upflows may be produced by the same impulsive events at the bases of ARs.

  9. Scattering resonance of elastic wave and low-frequency equivalent slow wave

    NASA Astrophysics Data System (ADS)

    Meng, X.; Liu, H.; Hu, T.; Yang, L.

    2015-12-01

    Transmitted wave occurs as fast p-wave and slow p-wave in certain conditions when seismic waves travel through inhomogeneous layers. Energy of slow p-waves is strongest at some frequency band, but rather weak at both high frequency band and low frequency band, called scattering resonance. For practical seismic exploration, the frequency of slow p-wave occurs is below 10Hz, which cannot be explained by Biot's theory which predicts existence of the slow p-wave at ultrasonic band in the porous media. The slow p-wave equation have been derived, but which only adapted to explaining slow p-wave in the ultrasonic band. Experimental observations exhibit that slow p-wave also exists in nonporous media but with enormous low-velocity interbeds. When vertical incidence, elastic wave is simplified as compressing wave, the generation of slow waves is independent on shear wave. In the case of flat interbed and gas bubble, Liu (2006) has studied the transmission of acoustic waves, and found that the slow waves below the 10Hz frequency band can be explained. In the case of general elastic anisotropy medium, the tiheoretical research on the generation of slow waves is insufficient. Aiming at this problem, this paper presents an exponential mapping method based on transmitted wave (Magnus 1954), which can successfully explain the generation of the slow wave transmission in that case. Using the prediction operator (Claerbout 1985) to represent the transmission wave, this can be derived as first order partial differential equation. Using expansions in the frequency domain and the wave number domain, we find that the solutions have different expressions in the case of weak scattering and strong scattering. Besides, the method of combining the prediction operator and the exponential map is needed to extend to the elastic wave equation. Using the equation (Frazer and Fryer 1984, 1987), we derive the exponential mapping solution for the prediction operator of the general elastic medium

  10. Sleep effects on slow-brain-potential reflections of associative learning.

    PubMed

    Verleger, Rolf; Ludwig, Janna; Kolev, Vasil; Yordanova, Juliana; Wagner, Ullrich

    2011-03-01

    Previous research has indicated that information acquired before sleep gets consolidated during sleep. This process of consolidation might be reflected after sleep in changed extent and topography of cortical activation during retrieval of information. Here, we designed an experiment to measure those changes by means of slow event-related EEG potentials (SPs). Retrieval of newly learnt verbal or spatial associations was tested both immediately after learning and two days later. In the night directly following immediate recall, participants either slept or stayed awake. In line with previous studies, SPs measured during retrieval from memory had parietal or left-frontal foci depending on whether the retrieved associations were spatial or verbal. However, contrary to our expectations, sleep-related consolidation did not further accentuate these content-specific topographic profiles. Rather, sleep modified SPs independently of the spatial or verbal type of learned association: SPs were reduced more after sleep than after waking specifically for those stimulus configurations that had been presented in the same combination at retrieval before sleep. The association-independent stimulus-specific effect might generally form a major component of sleep-related effects on memory. PMID:21182890

  11. Changes in cortical slow wave activity in healthy aging.

    PubMed

    Leirer, Vera Maria; Wienbruch, Christian; Kolassa, Stephan; Schlee, Winfried; Elbert, Thomas; Kolassa, Iris-Tatjana

    2011-09-01

    A number of studies have demonstrated enhanced slow wave activity associated with pathological brain function e.g. in stroke patients, schizophrenia, depression, Morbus Alzheimer, and post-traumatic stress disorder. However, the association between slow wave activity and healthy aging has remained largely unexplored. This study examined whether the frequency at which focal generators of delta waves appear in the healthy cerebral cortex changes with age and whether this measure relates to cognitive performance. We investigated 53 healthy individuals aged 18 to 89 years and assessed MEG during a resting condition. Generators of focal magnetic slow waves were localized. Results showed a significant influence of age: dipole density decreases with increasing age. The relationship between cognitive performance and delta dipole density was not significant. The results suggest that in healthy aging slow waves decrease with aging and emphasize the importance of age-matched control groups for further studies. Increased appearance of slow waves as a marker for pathological stages can only be detected in relation to a control group of the same age. PMID:21698438

  12. Finned-Ladder Slow-Wave Circuit for a TWT

    NASA Technical Reports Server (NTRS)

    Wilson, Jeffrey D.; Wintucky, Edwin G.; Kory, Carol L.

    2004-01-01

    A finned-ladder structure has been invented in an effort to improve the design of the slow-wave circuit of a traveling-wave tube (TWT). The point of departure for the design effort was a prototype TWT that contains a ring-plane slow-wave circuit (see Figure 1). The design effort was a response to the observation that despite the high-power capabilities of the ringplane TWT, its requirement for a high supply voltage and its low bandwidth have made it unacceptable for use outside a laboratory setting.

  13. Phase coupling between rhythmic slow activity and gamma characterizes mesiotemporal rapid-eye-movement sleep in humans.

    PubMed

    Clemens, Z; Weiss, B; Szucs, A; Eross, L; Rásonyi, G; Halász, P

    2009-09-29

    In the human sleep literature there is much controversy regarding the existence and the characteristics of hippocampal rhythmic slow activity (RSA). Generally the human RSA is believed to occur in short bursts of theta activity. An earlier study, however, reported mesiotemporal RSA during rapid-eye-movement (REM) sleep that instead of theta fell in the delta frequency band. We conjectured that if this RSA activity is indeed a human analogue of the animal hippocampal theta then characteristics associated with the animal theta should also be reflected in the human recordings. Here our aim was to examine possible phase coupling between mesiotemporal RSA and gamma activity during REM sleep. The study relied on nine epilepsy surgery candidates implanted with foramen ovale electrodes. Positive half-waves of the 1.5-3 Hz RSA were identified by an automatic algorithm during REM sleep. High-frequency activity was assessed for 11 consecutive 20 Hz-wide frequency bands between 20 and 240 Hz. Increase in high frequency activity was phase coupled with RSA in most frequency bands and patients. Such a phase coupling closely resembles that seen between theta and gamma in rodents. We consider this commonality to be an additional reason for regarding delta rather than theta as the human analogue of RSA in animals. PMID:19555738

  14. Standing slow magnetosonic waves in a dipole-like plasmasphere

    NASA Astrophysics Data System (ADS)

    Leonovich, A. S.; Kozlov, D. A.; Edemskiy, I. K.

    2010-09-01

    A problem of the structure and spectrum of standing slow magnetosonic waves in a dipole plasmasphere is solved. Both an analytical (in WKB approximation) and numerical solutions are found to the problem, for a distribution of the plasma parameters typical of the Earth's plasmasphere. The solutions allow us to treat the total electronic content oscillations registered above Japan as oscillations of one of the first harmonics of standing slow magnetosonic waves. Near the ionosphere the main components of the field of registered standing SMS waves are the plasma oscillations along magnetic field lines, plasma concentration oscillation and the related oscillations of the gas-kinetic pressure. The velocity of the plasma oscillations increases dramatically near the ionospheric conductive layer, which should result in precipitation of the background plasma particles. This may be accompanied by ionospheric F2 region airglows modulated with the periods of standing slow magnetosonic waves.

  15. Slow Wave Excitation in the ICRF and HHFW Regimes

    SciTech Connect

    Phillips, C. K.; Valeo, E. J.; Hosea, J. C.; LeBlanc, B. P.; Wilson, J. R.; Jaeger, E. F.; Berry, L. A.; Ryan, P. M.; Bonoli, P. T.; Wright, J. C.; Smithe, D. N.

    2011-12-23

    Theoretical considerations and high spatial resolution numerical simulations of radio frequency (rf) wave heating in tokamaks and in spherical toruses (ST) indicate that fast waves launched into tokamaks in the ion cyclotron range of frequencies (ICRF) or into spherical toruses in the high harmonic fast wave (HHFW) regime may excite a short wavelength slow mode inside of the plasma discharge due to the presence of hot electrons that satisfy the condition {omega}wave frequency, k{sub ||} is the local parallel component of the wave vector, and v{sub te} is the local electron thermal speed. This excited slow wave may be related to the electrostatic ion cyclotron wave that propagates for frequencies above the fundamental ion cyclotron frequency in warm plasmas or to a high frequency version of a kinetic Alfven wave. This slow wave, if physically real, would provide another path for rf power absorption in tokamaks and ST devices.

  16. Sleep in an Amazonian manatee, Trichechus inunguis.

    PubMed

    Mukhametov, L M; Lyamin, O I; Chetyrbok, I S; Vassilyev, A A; Diaz, R P

    1992-04-15

    For the first time, sleep was studied in a representative of the order of Sirenia. Slow wave sleep occupied 27%, and paradoxical sleep 1% of the total recording time in the Amazonian manatee. Trichechus inunguis. The circadian rhythmicity of sleep was pronounced. During the sleep period, the manatee woke up for a short time for each respiratory act. Interhemispheric asynchrony of the electrocortical slow wave activity was found. PMID:1582500

  17. Shock Formation of Slow Magnetosonic Waves in Coronal Plumes

    NASA Technical Reports Server (NTRS)

    Cuntz, Manfred; Suess, Steve; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We investigate the height of shock formation in coronal plumes for slow magnetosonic waves. The models take into account plume geometric spreading, heat conduction, and radiative damping. The wave parameters as well as the spreading functions of the plumes and the base magnetic field strengths are given by empirical constraints mostly from Solar and Heliospheric Observatory (SOHO)/ Ultraviolet Coronograph Spectrometer (UVCS), Extreme Ultraviolet Imaging Telescope (EIT), Michelson Doppler Imager (MDI), and Large Angle Spectrometric Coronagraph (LASCO). Our models show that shock formation occurs at relatively low coronal heights, typically within 1.2 RsuN, depending on the model parameters. The shock formation is calculated using the well-established wave breaking criterion given by the intersection of C+ characteristics in the space-time plane. Our models show that shock heating by slow magnetosonic waves is expected to be relevant at most heights in solar coronal plumes, although such waves are probably not the main energy supply mechanism.

  18. TeO2 slow surface acoustic wave Bragg cell

    NASA Astrophysics Data System (ADS)

    Yao, Shi-Kay

    1991-08-01

    A newly discovered slow acoustic surface wave (SAW) on a (-110) cut TeO2 surface is reported focusing on its properties studied using a PC based numerical method. It is concluded that the slow SAW is rather tolerant to crystal surface orientation errors and has unusually deep penetration of its shear component into the thickness of substrate, about 47 wavelengths for a half amplitude point. The deep shear field is considered to be beneficial for surface acoustooptic interaction with free propagating focused laser beams. Rotation of the substrate about the z-axis makes it possible to adjust a slow SAW velocity with the potential advantage of trading acoustic velocity for less acoustic attenuation. Wider-bandwidth long signal processing time Bragg cells may be feasible utilizing this trade-off. The slow SAW device is characterized by an extremely low power consumption which might be useful for compact portable or avionics signal processing equipment applications.

  19. Ostriches Sleep like Platypuses

    PubMed Central

    Lesku, John A.; Meyer, Leith C. R.; Fuller, Andrea; Maloney, Shane K.; Dell'Omo, Giacomo

    2011-01-01

    Mammals and birds engage in two distinct states of sleep, slow wave sleep (SWS) and rapid eye movement (REM) sleep. SWS is characterized by slow, high amplitude brain waves, while REM sleep is characterized by fast, low amplitude waves, known as activation, occurring with rapid eye movements and reduced muscle tone. However, monotremes (platypuses and echidnas), the most basal (or ‘ancient’) group of living mammals, show only a single sleep state that combines elements of SWS and REM sleep, suggesting that these states became temporally segregated in the common ancestor to marsupial and eutherian mammals. Whether sleep in basal birds resembles that of monotremes or other mammals and birds is unknown. Here, we provide the first description of brain activity during sleep in ostriches (Struthio camelus), a member of the most basal group of living birds. We found that the brain activity of sleeping ostriches is unique. Episodes of REM sleep were delineated by rapid eye movements, reduced muscle tone, and head movements, similar to those observed in other birds and mammals engaged in REM sleep; however, during REM sleep in ostriches, forebrain activity would flip between REM sleep-like activation and SWS-like slow waves, the latter reminiscent of sleep in the platypus. Moreover, the amount of REM sleep in ostriches is greater than in any other bird, just as in platypuses, which have more REM sleep than other mammals. These findings reveal a recurring sequence of steps in the evolution of sleep in which SWS and REM sleep arose from a single heterogeneous state that became temporally segregated into two distinct states. This common trajectory suggests that forebrain activation during REM sleep is an evolutionarily new feature, presumably involved in performing new sleep functions not found in more basal animals. PMID:21887239

  20. Sleep for cognitive enhancement

    PubMed Central

    Diekelmann, Susanne

    2014-01-01

    Sleep is essential for effective cognitive functioning. Loosing even a few hours of sleep can have detrimental effects on a wide variety of cognitive processes such as attention, language, reasoning, decision making, learning and memory. While sleep is necessary to ensure normal healthy cognitive functioning, it can also enhance performance beyond the boundaries of the normal condition. This article discusses the enhancing potential of sleep, mainly focusing on the domain of learning and memory. Sleep is known to facilitate the consolidation of memories learned before sleep as well as the acquisition of new memories to be learned after sleep. According to a widely held model this beneficial effect of sleep relies on the neuronal reactivation of memories during sleep that is associated with sleep-specific brain oscillations (slow oscillations, spindles, ripples) as well as a characteristic neurotransmitter milieu. Recent research indicates that memory processing during sleep can be boosted by (i) cueing memory reactivation during sleep; (ii) stimulating sleep-specific brain oscillations; and (iii) targeting specific neurotransmitter systems pharmacologically. Olfactory and auditory cues can be used, for example, to increase reactivation of associated memories during post-learning sleep. Intensifying neocortical slow oscillations (the hallmark of slow wave sleep (SWS)) by electrical or auditory stimulation and modulating specific neurotransmitters such as noradrenaline and glutamate likewise facilitates memory processing during sleep. With this evidence in mind, this article concludes by discussing different methodological caveats and ethical issues that should be considered when thinking about using sleep for cognitive enhancement in everyday applications. PMID:24765066

  1. Band formation in coupled-resonator slow-wave structures.

    PubMed

    Möller, Björn M; Woggon, Ulrike; Artemyev, Mikhail V

    2007-12-10

    Sequences of coupled-resonator optical waveguides (CROWs) have been examined as slow-wave structures. The formation of photonic bands in finite systems is studied in the frame of a coupled oscillator model. Several types of resonator size tuning in the system are evaluated in a systematical manner. We show that aperiodicities in sequences of coupled microspheres provide an additional degree of freedom for the design of photonic bands. PMID:19551030

  2. Conical slow wave antenna as a plasma source.

    PubMed

    Grubb, D P; Lovell, T

    1978-01-01

    A simple conical helix has been successfully employed as a slow wave structure to generate plasmas by electron cyclotron resonance heating (ECRH). The plasma is typical of plasmas created by ''Lisitano coil'' sources, n approximately 10(10)-10(12) cm(-3) with T(e) approximately 2-20 eV. This source, however, is much simpler to fabricate. The ease of fabrication allows the user some flexibility in designing the source to fit a specific plasma physics experiment. PMID:18698943

  3. Sleep

    MedlinePlus

    ... sleep deprivation? What are sleep myths? What are sleep disorders? Can certain diseases/conditions disrupt sleep? What is ... sleep deprivation? What are sleep myths? What are sleep disorders? Can certain diseases/conditions disrupt sleep? What is ...

  4. Reverberation, Storage, and Postsynaptic Propagation of Memories during Sleep

    ERIC Educational Resources Information Center

    Ribeiro, Sidarta; Nicolelis, Miguel A. L.

    2004-01-01

    In mammals and birds, long episodes of nondreaming sleep ("slow-wave" sleep, SW) are followed by short episodes of dreaming sleep ("rapid-eye-movement" sleep, REM). Both SW and REM sleep have been shown to be important for the consolidation of newly acquired memories, but the underlying mechanisms remain elusive. Here we review…

  5. Laminar analysis of the slow wave activity in the somatosensory cortex of anesthetized rats.

    PubMed

    Fiáth, Richárd; Kerekes, Bálint Péter; Wittner, Lucia; Tóth, Kinga; Beregszászi, Patrícia; Horváth, Domonkos; Ulbert, István

    2016-08-01

    Rhythmic slow waves characterize brain electrical activity during natural deep sleep and under anesthesia, reflecting the synchronous membrane potential fluctuations of neurons in the thalamocortical network. Strong evidence indicates that the neocortex plays an important role in the generation of slow wave activity (SWA), however, contributions of individual cortical layers to the SWA generation are still unclear. The anatomically correct laminar profiles of SWA were revealed under ketamine/xylazine anesthesia, with combined local field potential recordings, multiple-unit activity (MUA), current source density (CSD) and time-frequency analyses precisely co-registered with histology. The up-state related negative field potential wave showed the largest amplitude in layer IV, the CSD was largest in layers I and III, whereas MUA was maximal in layer V, suggesting spatially dissociated firing and synaptic/transmembrane processes in the rat somatosensory cortex. Up-state related firing could start in virtually any layers (III-VI) of the cortex, but were most frequently initiated in layer V. However, in a subset of experiments, layer IV was considerably active in initiating up-state related MUA even in the absence of somatosensory stimulation. Somatosensory stimulation further strengthened up-state initiation in layer IV. Our results confirm that cortical layer V firing may have a major contribution to the up-state generation of ketamine/xylazine-induced SWA, however, thalamic influence through the thalamorecipient layer IV can also play an initiating role, even in the absence of sensory stimulation. PMID:27177594

  6. Hierarchical nesting of slow oscillations, spindles and ripples in the human hippocampus during sleep

    PubMed Central

    Bonnefond, Mathilde; van der Meij, Roemer; Jensen, Ole; Deuker, Lorena; Elger, Christian E.; Axmacher, Nikolai; Fell, Juergen

    2015-01-01

    During systems-level consolidation, mnemonic representations initially reliant on the hippocampus are thought to migrate to neocortical sites for more permanent storage, with an eminent role of sleep for facilitating this information transfer. Mechanistically, consolidation processes have been hypothesized to rely on systematic interactions between the three cardinal neuronal oscillations characterizing non-rapid-eye-movement sleep: Under global control of de- and hyperpolarizing slow oscillations (SOs), sleep spindles may cluster hippocampal ripples for a precisely timed transfer of local information to the neocortex. Here we used direct intracranial electroencephalogram (iEEG) recordings from human epilepsy patients during natural sleep to test the assumption that SOs, spindles and ripples are functionally coupled in the hippocampus. Employing cross-frequency phase-amplitude coupling analyses, we first show that spindles are modulated by the up-state of SOs. Critically, spindles were found to in turn cluster ripples in their troughs, providing fine-tuned temporal frames for the hypothesized transfer of hippocampal memory traces. PMID:26389842

  7. Analysis of the power capacity of overmoded slow wave structures

    SciTech Connect

    Zhang, Dian; Zhang, Jun; Zhong, Huihuang; Jin, Zhenxing

    2013-07-15

    As the generated wavelength shortens, overmoded slow wave structures (SWSs) with large diameters are employed in O-type Cerenkov high power microwave (HPM) generators to achieve high power capacity. However, reported experimental results suggest that overmoded slow wave HPM generators working at millimeter wavelength output much lower power than those working at X-band do, despite the fact that the value of D/λ (here, D is the average diameter of SWSs and λ is the generated wavelength) of the former is much larger than that of the latter. In order to understand this, the characteristics of the power capacity of the TM{sub 0n} modes in overmoded SWSs are numerically investigated. Our analysis reveals the following facts. First, the power capacity of higher order TM{sub 0n} modes is apparently larger than that of TM{sub 01} mode. This is quite different from the conclusion got in the foregone report, in which the power capacity of overmoded SWSs is estimated by that of smooth cylindrical waveguides. Second, the rate at which the power capacity of TM{sub 01} mode in overmoded SWSs grows with diameter does not slow down as the TM{sub 01} field transforms from “volume wave” to “surface wave.” Third, once the diameter of overmoded SWSs and the beam voltage are fixed, the power capacity of TM{sub 01} wave drops as periodic length L shortens and the generated frequency rises, although the value of D/λ increases significantly. Therefore, it is necessary to investigate the capability of annular electron beam to interact efficiently with higher order TM{sub 0n} modes in overmoded SWSs if we want to improve the power capacity of overmoded O-type Cerenkov HPM generators working at high frequency.

  8. Propagation and damping of slow MHD waves in a flowing viscous coronal plasma

    NASA Astrophysics Data System (ADS)

    Kumar, Nagendra; Kumar, Anil; Murawski, K.

    2016-04-01

    We investigate the propagation of slow MHD waves in a flowing viscous solar coronal plasma. The compressive viscosity and steady flow along and opposite to the wave propagation are taken into account to study the damping of slow waves. We numerically solve the MHD equations by MacCormack method to examine the effect of steady flow on the damping of slow MHD waves in viscous solar coronal plasma. Amplitude of velocity perturbation and damping time of slow waves decrease with the increase in the value of Mach number. Flow causes a phase shift in the perturbed velocity amplitude and an increase in wave period. The damping of slow waves in flowing viscous plasma is stronger than the damping of waves in viscous plasma. Slow wave in backward flow damps earlier than the wave in forward flow.

  9. Slow magnetohydrodynamic waves in stratified and viscous plasmas

    SciTech Connect

    Ballai, Istvan; Erdelyi, Robert; Hargreaves, James

    2006-04-15

    The propagation of slow magnetohydrodynamic waves in vertical thin flux tubes embedded in a vertically stratified plasma in the presence of viscosity is shown here to be governed by the Klein-Gordon-Burgers (KGB) equation, which is solved in two limiting cases assuming an isothermal medium in hydrostatic equilibrium surrounded by a quiescent environment. The results presented here can be applied to, e.g., study the propagation of slow magnetohydrodynamic waves generated by the granular buffeting motion in thin magnetic photospheric tubes. When the variation in the reduced velocity occurs over typical lengths much larger than the gravitational scale height, the KGB equation can be reduced to a Klein-Gordon equation describing the propagation of an impulse followed by a wake oscillating with the frequency reduced by viscosity and the solution has no spatial or temporal decay. However, in the other limiting case, i.e., typical variations in the reduced velocity occur over characteristic lengths much smaller than the gravitational scale height, waves have a temporal and spatial decay.

  10. Compact FEL`s based on slow wave wigglers

    SciTech Connect

    Riyopoulos, S.

    1995-12-31

    Slow waves excited in magnetron-type cavities are attractive canditates as wigglers for compact Free Electron Lasers. Because of group velocities much below the speed of light, slow waves offer an order of magnitude increase in FEL gain under given circulating power in the wiggler resonator, compared to fast wave wigglers of similar period. In addition, they offer the versatility of operation either at modest beam energy via upshifing of the fundamental wavelength, or at low beam energy benefiting from the submillimeter wiggler harmonics. Because the main electron undulation is in the transverse direction for all spatial harmonics, the radiated power is increased by a factor {gamma}{sup 2} relative to the Smith-Purcell approach that relies on axial electron undulation. Technical advantages offered by magnetron-type wiggles are: the generation of the wiggler microwaves and the FEL interaction take place inside the same cavity, avoiding the issue of high power coupling between cavities; the excitation of wiggler microwaves relies on distributed electron emission from the cavity wall and does not require separate beam injection.

  11. Analysis of waves in the plasma guided by a periodical vane-type slow wave structure

    SciTech Connect

    Wu, T.J.; Kou, C.S.

    2005-10-01

    In this study, the dispersion relation has been derived to characterize the propagation of the waves in the plasma guided by a periodical vane-type slow wave structure. The plasma is confined by a quartz plate. Results indicate that there are two different waves in this structure. One is the plasma mode that originates from the plasma surface wave propagating along the interface between the plasma and the quartz plate, and the other is the guide mode that originally travels along the vane-type slow wave structure. In contrast to its original slow wave characteristics, the guide mode becomes a fast wave in the low-frequency portion of the passband, and there exists a cut-off frequency for the guide mode. The vane-type guiding structure has been shown to limit the upper frequency of the passband of the plasma mode, compared with that of the plasma surface wave. In addition, the passband of the plasma mode increases with the plasma density while it becomes narrower for the guide mode. The influences of the parameters of the guiding structure and plasma density on the propagation of waves are also presented.

  12. Slow Wave Conduction Patterns in the Stomach: From Waller’s Foundations to Current Challenges

    PubMed Central

    2015-01-01

    This review provides an overview of our understanding of motility and slow wave propagation in the stomach. It begins by reviewing seminal studies conducted by Walter Cannon and Augustus Waller on in vivo motility and slow wave patterns. Then our current understanding of slow wave patterns in common laboratory animals and humans is presented. The implications of slow wave dysrhythmic patterns that have been recorded in animals and patients suffering from gastroparesis are discussed. Finally, current challenges in experimental methods and techniques, slow wave modulation and the use of mathematical models are discussed. PMID:25313679

  13. A Bi-Frequency Linear Slow Wave Device

    NASA Astrophysics Data System (ADS)

    Simon, David; Zhang, Peng; Lau, Y. Y.; Greening, Geoff; Gilgenbach, Ronald; Hoff, Brad

    2014-10-01

    Bi-frequency sources are of interest to plasma processing, diagnostics, RF heating, and defense electronics. The recirculating planar magnetron has been modified to produce two frequencies using two different slow wave structures in the planar regions. To highlight the coupling in the two frequencies, we consider here a linear TWT driven by a sheet beam inside such a structure. The cold tube dispersion is derived and is compared favorably with HFSS. The hot tube dispersion has also been derived, and is being compared with MAGIC simulations. Various nonlinear effects are explored, such as harmonic generation, parametric amplification, and intermodulation. This work was supported by ONR and AFOSR.

  14. Topography of Slow Sigma Power during Sleep is Associated with Processing Speed in Preschool Children

    PubMed Central

    Doucette, Margaret R.; Kurth, Salome; Chevalier, Nicolas; Munakata, Yuko; LeBourgeois, Monique K.

    2015-01-01

    Cognitive development is influenced by maturational changes in processing speed, a construct reflecting the rapidity of executing cognitive operations. Although cognitive ability and processing speed are linked to spindles and sigma power in the sleep electroencephalogram (EEG), little is known about such associations in early childhood, a time of major neuronal refinement. We calculated EEG power for slow (10–13 Hz) and fast (13.25–17 Hz) sigma power from all-night high-density electroencephalography (EEG) in a cross-sectional sample of healthy preschool children (n = 10, 4.3 ± 1.0 years). Processing speed was assessed as simple reaction time. On average, reaction time was 1409 ± 251 ms; slow sigma power was 4.0 ± 1.5 μV2; and fast sigma power was 0.9 ± 0.2 μV2. Both slow and fast sigma power predominated over central areas. Only slow sigma power was correlated with processing speed in a large parietal electrode cluster (p < 0.05, r ranging from −0.6 to −0.8), such that greater power predicted faster reaction time. Our findings indicate regional correlates between sigma power and processing speed that are specific to early childhood and provide novel insights into the neurobiological features of the EEG that may underlie developing cognitive abilities. PMID:26556377

  15. Energy and energy flux in axisymmetric slow and fast waves

    NASA Astrophysics Data System (ADS)

    Moreels, M. G.; Van Doorsselaere, T.; Grant, S. D. T.; Jess, D. B.; Goossens, M.

    2015-06-01

    Aims: We aim to calculate the kinetic, magnetic, thermal, and total energy densities and the flux of energy in axisymmetric sausage modes. The resulting equations should contain as few parameters as possible to facilitate applicability for different observations. Methods: The background equilibrium is a one-dimensional cylindrical flux tube model with a piecewise constant radial density profile. This enables us to use linearised magnetohydrodynamic equations to calculate the energy densities and the flux of energy for axisymmetric sausage modes. Results: The equations used to calculate the energy densities and the flux of energy in axisymmetric sausage modes depend on the radius of the flux tube, the equilibrium sound and Alfvén speeds, the density of the plasma, the period and phase speed of the wave, and the radial or longitudinal components of the Lagrangian displacement at the flux tube boundary. Approximate relations for limiting cases of propagating slow and fast sausage modes are also obtained. We also obtained the dispersive first-order correction term to the phase speed for both the fundamental slow body mode under coronal conditions and the slow surface mode under photospheric conditions. Appendix A is available in electronic form at http://www.aanda.org

  16. The Propagation of Slow Wave Potentials in Pea Epicotyls.

    PubMed Central

    Stahlberg, R.; Cosgrove, D. J.

    1997-01-01

    Slow wave potentials are considered to be electric long-distance signals specific for plants, although there are conflicting ideas about a chemical, electrical, or hydraulic mode of propagation. These ideas were tested by comparing the propagation of hydraulic and electric signals in epicotyls of pea (Pisum sativum L). A hydraulic signal in the form of a defined step increase in xylem pressure (Px) was applied to the root of intact seedlings and propagated nearly instantly through the epicotyl axis while its amplitude decreased with distance from the pressure chamber. This decremental propagation was caused by a leaky xylem and created an axial Px gradient in the epicotyl. Simultaneously along the epicotyl surface, depolarizations appeared with lag times that increased acropetally with distance from the pressure chamber from 5 s to 3 min. When measured at a constant distance, the lag times increased as the size of the applied pressure steps decreased. We conclude that the Px gradient in the epicotyl caused local depolarizations with acropetally increasing lag times, which have the appearance of an electric signal propagating with a rate of 20 to 30 mm min-1. This static description of the slow wave potentials challenges its traditional classification as a propagating electric signal. PMID:12223601

  17. Mild Airflow Limitation during N2 Sleep Increases K-complex Frequency and Slows Electroencephalographic Activity

    PubMed Central

    Nguyen, Chinh D.; Wellman, Andrew; Jordan, Amy S.; Eckert, Danny J.

    2016-01-01

    Study Objectives: To determine the effects of mild airflow limitation on K-complex frequency and morphology and electroencephalogram (EEG) spectral power. Methods: Transient reductions in continuous positive airway pressure (CPAP) during stable N2 sleep were performed to induce mild airflow limitation in 20 patients with obstructive sleep apnea (OSA) and 10 healthy controls aged 44 ± 13 y. EEG at C3 and airflow were measured in 1-min windows to quantify K-complex properties and EEG spectral power immediately before and during transient reductions in CPAP. The frequency and morphology (amplitude and latency of P200, N550 and N900 components) of K-complexes and EEG spectral power were compared between conditions. Results: During mild airflow limitation (18% reduction in peak inspiratory airflow from baseline, 0.38 ± 0.11 versus 0.31 ± 0.1 L/sec) insufficient to cause American Academy of Sleep Medicine-defined cortical arousal, K-complex frequency (9.5 ± 4.5 versus 13.7 ± 6.4 per min, P < 0.01), N550 amplitude (25 ± 3 versus 27 ± 3 μV, P < 0.01) and EEG spectral power (delta: 147 ± 48 versus 230 ± 99 μV2, P < 0.01 and theta bands: 31 ± 14 versus 34 ± 13 μV2, P < 0.01) significantly increased whereas beta band power decreased (14 ± 5 versus 11 ± 4 μV2, P < 0.01) compared to the preceding non flow-limited period on CPAP. K-complex frequency, morphology, and timing did not differ between patients and controls. Conclusion: Mild airflow limitation increases K-complex frequency, N550 amplitude, and spectral power of delta and theta bands. In addition to providing mechanistic insight into the role of mild airflow limitation on K-complex characteristics and EEG activity, these findings may have important implications for respiratory conditions in which airflow limitation during sleep is common (e.g., snoring and OSA). Citation: Nguyen CD, Wellman A, Jordan AS, Eckert DJ. Mild airflow limitation during N2 sleep increases k-complex frequency and slows

  18. β-amyloid disrupts human NREM slow waves and related hippocampus-dependent memory consolidation

    PubMed Central

    Mander, Bryce A.; Marks, Shawn M.; Vogel, Jacob W.; Rao, Vikram; Lu, Brandon; Saletin, Jared M.; Ancoli-Israel, Sonia; Jagust, William J.; Walker, Matthew P.

    2015-01-01

    Independent evidence associates β-amyloid pathology with both NREM sleep disruption and memory impairment in older adults. However, whether the influence of β-amyloid pathology on hippocampus-dependent memory is, in part, driven by impairments of NREM slow wave activity (SWA) and associated overnight memory consolidation is unknown. Here, we show that β-amyloid burden within medial prefrontal cortex (mPFC) is significantly correlated with the severity of impairment in NREM SWA generation. Moreover, reduced NREM SWA generation was further associated with impaired overnight memory consolidation and impoverished hippocampal-neocortical memory transformation. Furthermore, structural equation models revealed that the association between mPFC β-amyloid pathology and impaired hippocampus-dependent memory consolidation is not direct, but instead, statistically depends on the intermediary factor of diminished NREM SWA. By linking β-amyloid pathology with impaired NREM SWA, these data implicate sleep disruption as a novel mechanistic pathway through which β-amyloid pathology may contribute to hippocampus-dependent cognitive decline in the elderly. PMID:26030850

  19. β-amyloid disrupts human NREM slow waves and related hippocampus-dependent memory consolidation.

    PubMed

    Mander, Bryce A; Marks, Shawn M; Vogel, Jacob W; Rao, Vikram; Lu, Brandon; Saletin, Jared M; Ancoli-Israel, Sonia; Jagust, William J; Walker, Matthew P

    2015-07-01

    Independent evidence associates β-amyloid pathology with both non-rapid eye movement (NREM) sleep disruption and memory impairment in older adults. However, whether the influence of β-amyloid pathology on hippocampus-dependent memory is, in part, driven by impairments of NREM slow wave activity (SWA) and associated overnight memory consolidation is unknown. Here we show that β-amyloid burden in medial prefrontal cortex (mPFC) correlates significantly with the severity of impairment in NREM SWA generation. Moreover, reduced NREM SWA generation was further associated with impaired overnight memory consolidation and impoverished hippocampal-neocortical memory transformation. Furthermore, structural equation models revealed that the association between mPFC β-amyloid pathology and impaired hippocampus-dependent memory consolidation was not direct, but instead statistically depended on the intermediary factor of diminished NREM SWA. By linking β-amyloid pathology with impaired NREM SWA, these data implicate sleep disruption as a mechanistic pathway through which β-amyloid pathology may contribute to hippocampus-dependent cognitive decline in the elderly. PMID:26030850

  20. Comparing the Robustness of High-Frequency Traveling-Wave Tube Slow-Wave Circuits

    NASA Technical Reports Server (NTRS)

    Chevalier, Christine T.; Wilson, Jeffrey D.; Kory, Carol L.

    2007-01-01

    A three-dimensional electromagnetic field simulation software package was used to compute the cold-test parameters, phase velocity, on-axis interaction impedance, and attenuation, for several high-frequency traveling-wave tube slow-wave circuit geometries. This research effort determined the effects of variations in circuit dimensions on cold-test performance. The parameter variations were based on the tolerances of conventional micromachining techniques.

  1. Sleep spindles and hippocampal functional connectivity in human NREM sleep.

    PubMed

    Andrade, Kátia C; Spoormaker, Victor I; Dresler, Martin; Wehrle, Renate; Holsboer, Florian; Sämann, Philipp G; Czisch, Michael

    2011-07-13

    We investigated human hippocampal functional connectivity in wakefulness and throughout non-rapid eye movement sleep. Young healthy subjects underwent simultaneous EEG and functional magnetic resonance imaging (fMRI) measurements at 1.5 T under resting conditions in the descent to deep sleep. Continuous 5 min epochs representing a unique sleep stage (i.e., wakefulness, sleep stages 1 and 2, or slow-wave sleep) were extracted. fMRI time series of subregions of the hippocampal formation (HF) (cornu ammonis, dentate gyrus, and subiculum) were extracted based on cytoarchitectonical probability maps. We observed sleep stage-dependent changes in HF functional coupling. The HF was integrated to variable strength in the default mode network (DMN) in wakefulness and light sleep stages but not in slow-wave sleep. The strongest functional connectivity between the HF and neocortex was observed in sleep stage 2 (compared with both slow-wave sleep and wakefulness). We observed a strong interaction of sleep spindle occurrence and HF functional connectivity in sleep stage 2, with increased HF/neocortical connectivity during spindles. Moreover, the cornu ammonis exhibited strongest functional connectivity with the DMN during wakefulness, while the subiculum dominated hippocampal functional connectivity to frontal brain regions during sleep stage 2. Increased connectivity between HF and neocortical regions in sleep stage 2 suggests an increased capacity for possible global information transfer, while connectivity in slow-wave sleep is reflecting a functional system optimal for segregated information reprocessing. Our data may be relevant to differentiating sleep stage-specific contributions to neural plasticity as proposed in sleep-dependent memory consolidation. PMID:21753010

  2. Detection of the Recovery Phase of in vivo Gastric Slow Wave Recordings

    PubMed Central

    Paskaranandavadivel, Niranchan; Pan, Xingzheng; Du, Peng; O’Grady, Gregory; Cheng, Leo K.

    2016-01-01

    Gastric motility is coordinated by bio-electrical events known as slow waves. Abnormalities in slow waves are linked to major functional and motility disorders. In recent years, the use of high-resolution (HR) recordings have provided a unique view of spatiotemporal activation profiles of normal and dysrhythmic slow wave activity. To date, in vivo studies of gastric slow wave activity have primarily focused on the activation phase of the slow wave event. In this study, the recovery phase of slow waves was investigated through the use of HR recording techniques. The recovery phase of the slow wave event was detected through the use of the signal derivative, computed via a wavelet transform. The activation to recovery interval (ARi) metric was computed as a difference between the recovery time and activation time. The detection method was validated with synthetic slow wave signals of varying morphologies with the addition of synthetic ventilator and high frequency noise. The methods was then applied to HR experimental porcine gastric slow wave recordings. Ventilator noise more than 10% of the slow wave amplitude affected the estimation of the ARi metric. Signal to noise ratio below 3 dB affected the ARi metric, but with minor deviation in accuracy. Experimental ARi values ranged from 3.7–4.7 s from three data sets, with significant differences across them. PMID:26737682

  3. A slow slip event triggered by teleseismic surface waves

    NASA Astrophysics Data System (ADS)

    Itaba, Satoshi; Ando, Ryosuke

    2011-11-01

    In recent years slow slip events (SSE) have been observed to occur at regular intervals on the deep portions of subduction zone interfaces. These are accompanied by seismic tremor that occurs over their duration. It has been observed that tremor activity shows transient modulations in response to earth tides and the passage of seismic waves from distant earthquakes. Here we show, for the first time, geodetic evidence for the triggering of an interplate SSE itself by teleseismic surface waves. This SSE, in southwest Japan, which had an equivalent magnitude Mw 5.3 and duration of 1.5 days, was triggered by the surface waves of a Mw 7.6 earthquake in Tonga. This evidence was captured by a newly deployed sensitive strainmeter network. The triggered SSE occurred on a place on the plate interface where the recurrence time for such events had almost expired, whereas other regions, at up to 90% of the recurrence time, were not triggered. This provides information for the conditions for triggering and generation of SSEs and, perhaps, for regular earthquakes.

  4. SLOW MAGNETOACOUSTIC WAVES IN TWO-RIBBON FLARES

    SciTech Connect

    Nakariakov, V. M.; Zimovets, I. V.

    2011-04-01

    We demonstrate that disturbances observed to propagate along the axis of the arcade in two-ribbon solar flares at the speed of a few tens of km s{sup -1}, well below the Alfven and sound speeds, can be interpreted in terms of slow magnetoacoustic waves. The waves can propagate across the magnetic field, parallel to the magnetic neutral line, because of the wave-guiding effect due to the reflection from the footpoints. The perpendicular group speed of the perturbation is found to be a fraction of the sound speed, which is consistent with observations. The highest value of the group speed grows with the increase in the ratio of the sound and Alfven speeds. For a broad range of parameters, the highest value of the group speed corresponds to the propagation angle of 25 deg. - 28 deg. to the magnetic field. This effect can explain the temporal and spatial structure of quasi-periodic pulsations observed in two-ribbon flares.

  5. Stimulating forebrain communications: Slow sinusoidal electric fields over frontal cortices dynamically modulate hippocampal activity and cortico-hippocampal interplay during slow-wave states.

    PubMed

    Greenberg, Anastasia; Whitten, Tara A; Dickson, Clayton T

    2016-06-01

    Slow-wave states are characterized by the most global physiological phenomenon in the mammalian brain, the large-amplitude slow oscillation (SO; ~1Hz) composed of alternating states of activity (ON/UP states) and silence (OFF/DOWN states) at the network and single cell levels. The SO is cortically generated and appears as a traveling wave that can propagate across the cortical surface and can invade the hippocampus. This cortical rhythm is thought to be imperative for sleep-dependent memory consolidation, potentially through increased interactions with the hippocampus. The SO is correlated with learning and its presumed enhancement via slow rhythmic electrical field stimulation improves subsequent mnemonic performance. However, the mechanism by which such field stimulation influences the dynamics of ongoing cortico-hippocampal communication is unknown. Here we show - using multi-site recordings in urethane-anesthetized rats - that sinusoidal electrical field stimulation applied to the frontal region of the cerebral cortex creates a platform for improved cortico-hippocampal communication. Moderate-intensity field stimulation entrained hippocampal slow activity (likely by way of the temporoammonic pathway) and also increased sharp-wave ripples, the signature memory replay events of the hippocampus, and further increased cortical spindles. Following cessation of high-intensity stimulation, SO interactions in the cortical-to-hippocampal direction were reduced, while the reversed hippocampal-to-cortical communication at both SO and gamma bandwidths was enhanced. Taken together, these findings suggest that cortical field stimulation may function to boost memory consolidation by strengthening cortico-hippocampal and hippocampo-cortical interplay at multiple nested frequencies in an intensity-dependent fashion. PMID:26947518

  6. Sustained Use of CPAP Slows Deterioration of Cognition, Sleep, and Mood in Patients with Alzheimer's Disease and Obstructive Sleep Apnea: A Preliminary Study

    PubMed Central

    Cooke, Jana R.; Ayalon, Liat; Palmer, Barton W.; Loredo, Jose S.; Corey-Bloom, Jody; Natarajan, Loki; Liu, Lianqi; Ancoli-Israel, Sonia

    2009-01-01

    Introduction: Obstructive sleep apnea (OSA) is common among patients with Alzheimer's disease (AD). Untreated OSA exacerbates the cognitive and functional deficits. Continuous positive airway pressure (CPAP) has recently been shown to have beneficial effects on cognition in AD. Little attention has focused on the long-term benefits of CPAP in these patients. Methods: This was an exploratory study of sustained CPAP use (mean use = 13.3 months, SD = 5.2) among a subset of participants from an initial 6-week randomized clinical trial (RCT) of CPAP in patients with mild to moderate AD. Follow-up included 5 patients who continued CPAP (CPAP+) after completion of the RCT and 5 patients who discontinued CPAP (CPAP−), matched by time of completion of the initial study. A neuropsychological test battery and sleep/mood questionnaires were administered and effect sizes were calculated. Results: Even with a small sample size, sustained CPAP use resulted in moderate-to-large effect sizes. Compared to the CPAP− group, the CPAP+ group showed less cognitive decline with sustained CPAP use, stabilization of depressive symptoms and daytime somnolence, and significant improvement in subjective sleep quality. Caregivers of the CPAP+ group also reported that their own sleep was better when compared to the final RCT visit and that their patients psychopathological behavior was improved. Conclusion: The results of this preliminary study raise the possibility that sustained, long-term CPAP treatment for patients with AD and OSA may result in lasting improvements in sleep and mood as well as a slowing of cognitive deterioration. Prospective randomized controlled research trials evaluating these hypotheses are needed. Citation: Cooke JR; Ayalon L; Palmer BW; Loredo JS; Corey-Bloom J; Natarajan L; Liu L; Ancoli-Israel S. Sustained use of CPAP slows deterioration of cognition, sleep, and mood in patients with Alzheimer's disease and obstructive sleep apnea: a preliminary study. J Clin

  7. Sleep and cardiac rhythm in the gray seal.

    PubMed

    Ridgway, S H; Harrison, R J; Joyce, P L

    1975-02-14

    Telemetric studies of electroencephalograms, electrocardiograms, and electroculograms and concurrent observations of behavior revealed that seals can sleep underwater, on the surface, or while hauled out. Rapid eye movement preceded slow wave sleep and was accompanied by increased respiratory rate and rhythmic tachycardia. While slow wave sleep occurred under all sleep conditions, rapid eye movement occurred only when a seal was hanging at the water surface or hauled out, never underwater. PMID:163484

  8. Electroencephalogram slowing predicts neurodegeneration in rapid eye movement sleep behavior disorder.

    PubMed

    Rodrigues Brazète, Jessica; Gagnon, Jean-François; Postuma, Ronald B; Bertrand, Josie-Anne; Petit, Dominique; Montplaisir, Jacques

    2016-01-01

    A large proportion of patients with idiopathic rapid eye movement sleep behavior disorder (iRBD) develop a synucleinopathy, mostly Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. Therefore, identifying markers of neurodegeneration in iRBD could have major implications. We aimed to assess the usefulness of electroencephalography (EEG) spectral analysis performed during wakefulness for predicting the development of a neurodegenerative disease in iRBD. Fifty-four iRBD patients, 28 of whom developed Parkinson's disease, multiple system atrophy, or dementia with Lewy bodies (mean follow-up: 3.5 years), and 30 healthy controls underwent at baseline a resting-state waking EEG recording, neurological exam, and neuropsychological assessment. Absolute and relative spectral powers were analyzed for 5 frequency bands in frontal, central, parietal, temporal, and occipital regions. The slow-to-fast [(δ + θ)/(β1 + β2)] power ratio for each of the 5 cortical regions and the dominant occipital frequency were calculated as an index of cortical slowing. Patients who developed disease showed higher absolute delta and theta power in all 5 cortical regions compared to disease-free patients and controls. The slow-to-fast power ratio was higher in all regions in patients who developed disease than in the 2 other groups. Moreover, patients who developed disease had a slower dominant occipital frequency compared to controls. The only significant difference observed between disease-free iRBD patients and controls was higher absolute delta power in frontal and occipital regions in iRBD patients. Specific EEG abnormalities were identified during wakefulness in iRBD patients who later developed a synucleinopathy. EEG slowing is a promising marker of neurodegeneration in iRBD patients. PMID:26545633

  9. Slow Wave Vane Structure with Elliptical Cross-Section Slots, an Analysis

    NASA Technical Reports Server (NTRS)

    Kosmahl, Henry G.

    1994-01-01

    Mathematical analysis of the wave equation in cylinders with elliptical cross-section slots was performed. Compared to slow wave structures with rectangular slots higher impedance and lower power dissipation losses are evident. These features could lead to improved designs of traveling wave magnetrons and gigahertz backward-wave oscillators as well as linear traveling wave tubes with relatively shallow slots.

  10. Nonlinear theory of slow cyclotron wave interaction in folded waveguide

    SciTech Connect

    Ganguly, A.K.; Choi, J.J.

    1995-12-31

    A three-dimensional non-linear theory is presented for the generation of broadband radiation from slow cyclotron wave interaction in a folded waveguide. The serpentine structure is formed by folding a rectangular waveguide so that the orientation of the magnetic changes (H-plane bend) instead of the conventional E-plane bend configuration where the orientation of the electric field changes. The H-plane bend structure can use larger beam tunnel without distorting the rf field structure and generate higher output power. Numerical results will be shown for the TE{sub 10} mode propagation in an unridged and a double ridged waveguide. For a 61.5 kV, 3 A beam with {alpha}=1.0 and {Delta}v{sub z}/v{sub z}=0, calculations show an efficiency of 25% with 20% bandwidth and an efficiency of 35% at 10% bandwidth. The efficiency and bandwidth is relatively unchanged up to a beam axial velocity spread of 2%. The bandwidth can be further increased by mode coalescing techniques. Multistage operation is necessary to avoid backward wave oscillation.

  11. Sleep in pregnancy.

    PubMed

    Richardson, P

    1996-07-01

    The article examines relationships between pregnancy and maternal sleep. Specifically, sleep as a restorative process is considered with regard for the metabolic and arousal demands of childbearing. The analysis draws attention to the limited number of studies in the area and the need for greater research interest in pregnancy sleep phenomena. The available evidence indicates that maternal slow-wave and rapid eye movement which are key to anabolic activity and neural-cerebral recharge, are protected throughout pregnancy until perhaps the last 3 to 4 weeks before delivery. The sleep disturbances about which term gravidas complain appear to be based on increased periods of wakefulness after sleep onset. PMID:8717994

  12. SLOW MAGNETOACOUSTIC WAVES OBSERVED ABOVE A QUIET-SUN REGION IN A DARK CAVITY

    SciTech Connect

    Liu Jiajia; Zhou Zhenjun; Wang Yuming; Liu Rui; Liao Chijian; Shen Chenglong; Zheng Huinan; Miao Bin; Su Zhenpeng; Wang, S.; Wang Bin E-mail: ymwang@ustc.edu.cn

    2012-10-20

    Waves play a crucial role in diagnosing the plasma properties of various structures in the solar corona and coronal heating. Slow magnetoacoustic (MA) waves are one of the important types of magnetohydrodynamic waves. In past decades, numerous slow MA waves were detected above active regions and coronal holes, but were rarely found elsewhere. Here, we investigate a 'tornado'-like structure consisting of quasi-periodic streaks within a dark cavity at about 40-110 Mm above a quiet-Sun region on 2011 September 25. Our analysis reveals that these streaks are actually slow MA wave trains. The properties of these wave trains, including phase speed, compression ratio, and kinetic energy density, are similar to those of the reported slow MA waves, except that the period of these waves is about 50 s, much shorter than the typical reported values (3-5 minutes).

  13. Alpha-wave frequency characteristics in health and insomnia during sleep.

    PubMed

    Schwabedal, Justus T C; Riedl, Maik; Penzel, Thomas; Wessel, Niels

    2016-06-01

    Appearances of alpha waves in the sleep electrencephalogram indicate physiological, brief states of awakening that lie in between wakefulness and sleep. These microstates may also cause the loss in sleep quality experienced by individuals suffering from insomnia. To distinguish such pathological awakenings from physiological ones, differences in alpha-wave characteristics between transient awakening and wakefulness observed before the onset of sleep were studied. In polysomnographic datasets of sleep-healthy participants (n = 18) and patients with insomnia (n = 10), alpha waves were extracted from the relaxed, wake state before sleep onset, wake after sleep-onset periods and arousals of sleep. In these, alpha frequency and variability were determined as the median and standard deviation of inverse peak-to-peak intervals. Before sleep onset, patients with insomnia showed a decreased alpha variability compared with healthy participants (P < 0.05). After sleep onset, both groups showed patterns of decreased alpha frequency that was lower for wake after sleep-onset periods of shorter duration. For patients with insomnia, alpha variability increased for short wake after sleep-onset periods. Major differences between the two groups were encountered during arousal. In particular, the alpha frequency in patients with insomnia rebounded to wake levels, while the frequency in healthy participants remained at the reduced level of short wake after sleep-onset periods. Reductions in alpha frequency during wake after sleep-onset periods may be related to the microstate between sleep and wakefulness that was described for such brief awakenings. Reduced alpha variability before sleep may indicate a dysfunction of the alpha generation mechanism in insomnia. Alpha characteristics may also prove valuable in the study of other sleep and attention disorders. PMID:26781046

  14. A 0.14 THz relativistic coaxial overmoded surface wave oscillator with metamaterial slow wave structure

    SciTech Connect

    Guo, Weijie; Wang, Jianguo Chen, Zaigao; Cai, Libing; Wang, Yue; Wang, Guangqiang; Qiao, Hailiang

    2014-12-15

    This paper presents a new kind of device for generating the high power terahertz wave by using a coaxial overmoded surface wave oscillator with metamaterial slow wave structure (SWS). A metallic metamaterial SWS is used to avoid the damage of the device driven by a high-voltage electron beam pulse. The overmoded structure is adopted to make it much easy to fabricate and assemble the whole device. The coaxial structure is used to suppress the mode competition in the overmoded device. Parameters of an electron beam and geometric structure are provided. Particle-in-cell simulation results show that the high power terahertz wave at the frequency of 0.14 THz is generated with the output power 255 MW and conversion efficiency about 21.3%.

  15. Characterization of slow waves generated by myenteric interstitial cells of Cajal of the rabbit small intestine.

    PubMed

    Kito, Yoshihiko; Mitsui, Retsu; Ward, Sean M; Sanders, Kenton M

    2015-03-01

    Slow waves (slow wavesICC) were recorded from myenteric interstitial cells of Cajal (ICC-MY) in situ in the rabbit small intestine, and their properties were compared with those of mouse small intestine. Rabbit slow wavesICC consisted of an upstroke depolarization followed by a distinct plateau component. Ni(2+) and nominally Ca(2+)-free solutions reduced the rate-of-rise and amplitude of the upstroke depolarization. Replacement of Ca(2+) with Sr(2+) enhanced the upstroke component but decreased the plateau component of rabbit slow wavesICC. In contrast, replacing Ca(2+) with Sr(2+) decreased both components of mouse slow wavesICC. The plateau component of rabbit slow wavesICC was inhibited in low-extracellular-Cl(-)-concentration (low-[Cl(-)]o) solutions and by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), an inhibitor of Cl(-) channels, cyclopiazonic acid (CPA), an inhibitor of internal Ca(2+) pumps, or bumetanide, an inhibitor of Na(+)-K(+)-2Cl(-) cotransporter (NKCC1). Bumetanide also inhibited the plateau component of mouse slow wavesICC. NKCC1-like immunoreactivity was observed mainly in ICC-MY in the rabbit small intestine. Membrane depolarization with a high-K(+) solution reduced the upstroke component of rabbit slow wavesICC. In cells depolarized with elevated external K(+), DIDS, CPA, and bumetanide blocked slow wavesICC. These results suggest that the upstroke component of rabbit slow wavesICC is partially mediated by voltage-dependent Ca(2+) influx, whereas the plateau component is dependent on Ca(2+)-activated Cl(-) efflux. NKCC1 is likely to be responsible for Cl(-) accumulation in ICC-MY. The results also suggest that the mechanism of the upstroke component differs in rabbit and mouse slow wavesICC in the small intestine. PMID:25540230

  16. A Multistudy Analysis of the Effects of Early Cocaine Abstinence on Sleep

    PubMed Central

    Matuskey, D; Pittman, B; Forselius, E; Malison, RT; Morgan, PT

    2010-01-01

    Objective To describe the sleep patterns of early cocaine abstinence in chronic users by polysomnographic and subjective measures. Methods 28 cocaine-dependent participants (ages 24-55) underwent polysomnographic sleep (PSG) recording on the 1st, 2nd and 3rd weeks of abstinence on a research dedicated inpatient facility. Objective measures of total sleep time, total REM time, slow wave sleep, sleep efficiency and a subjective measure (sleep quality) along with demographic data were collected from three different long term research studies over a five year period. Data were reanalyzed to allow greater statistical power for comparisons. Results Progressive weeks of abstinence had main effects on all assessed PSG sleep measures showing decreased total sleep time, REM sleep, stage 1 and 2 sleep, and sleep efficiency; increases in sleep onset and REM latencies and a slight increase in slow-wave sleep time were also present. Total sleep time and slow wave sleep were negatively associated with years of cocaine use. Total sleep time was positively associated with the amount of current ethanol use. Sex differences were found with females having more total REM time and an increase at a near significance level in slow wave sleep. Subjective measures were reported as improving with increasing abstinence over the same time period. Conclusions Chronic cocaine users show a general deterioration in objective sleep measures over a three-week period despite an increase in subjective overall sleep quality providing further evidence for “occult insomnia” during early cocaine abstinence. PMID:21144676

  17. Transcranial slow oscillation stimulation during NREM sleep enhances acquisition of the radial maze task and modulates cortical network activity in rats

    PubMed Central

    Binder, Sonja; Rawohl, Julia; Born, Jan; Marshall, Lisa

    2014-01-01

    Slow wave sleep, hallmarked by the occurrence of slow oscillations (SO), plays an important role for the consolidation of hippocampus-dependent memories. Transcranial stimulation by weak electric currents oscillating at the endogenous SO frequency (SO-tDCS) during post-learning sleep was previously shown by us to boost SO activity and improve the consolidation of hippocampus-dependent memory in human subjects. Here, we aimed at replicating and extending these results to a rodent model. Rats were trained for 12 days at the beginning of their inactive phase in the reference memory version of the radial arm maze. In a between subjects design, animals received SO-tDCS over prefrontal cortex (PFC) or sham stimulation within a time frame of 1 h during subsequent non-rapid eye movement (NREM) sleep. Applied over multiple daily sessions SO-tDCS impacted cortical network activity as measured by EEG and behavior: at the EEG level, SO-tDCS enhanced post-stimulation upper delta (2–4 Hz) activity whereby the first stimulations of each day were preferentially affected. Furthermore, commencing on day 8, SO-tDCS acutely decreased theta activity indicating long-term effects on cortical networks. Behaviorally, working memory for baited maze arms was enhanced up to day 4, indicating enhanced consolidation of task-inherent rules, while reference memory errors did not differ between groups. Taken together, we could show here for the first time an effect of SO-tDCS during NREM sleep on cognitive functions and on cortical activity in a rodent model. PMID:24409131

  18. Enhanced traveling wave amplification of co-planar slow wave structure by extended phase-matching

    SciTech Connect

    Palm, Andrew; Sirigiri, Jagadishwar; Shin, Young-Min

    2015-09-15

    The electron beam co-propagating with slow waves in a staggered double grating array (SDGA) efficiently amplifies millimeter and sub-millimeter waves over a wide spectrum. Our theoretical and numerical analyses show that the power amplification in the fundamental passband is enhanced by the extended beam-wave phase-matching. Particle-in-cell simulations on the SDGA slow wave structure, designed with 10.4 keV and 50–100 mA sheet beam, indicate that maintaining beam-wave synchronization along the entire length of the circuit improves the gain by 7.3% leading to a total gain of 28 dB, corresponding to 62 W saturated power at the middle of operating band, and a 3-dB bandwidth of 7 GHz with 10.5% at V-band (73.5 GHz center frequency) with saturated peak power reaching 80 W and 28 dB at 71 GHz. These results also show a reasonably good agreement with analytic calculations based on Pierce small signal gain theory.

  19. Reduction in cortical gamma synchrony during depolarized state of slow wave activity in mice

    PubMed Central

    Hwang, Eunjin; McNally, James M.; Choi, Jee Hyun

    2013-01-01

    EEG gamma band oscillations have been proposed to account for the neural synchronization crucial for perceptual integration. While increased gamma power and synchronization is generally observed during cognitive tasks performed during wake, several studies have additionally reported increased gamma power during sleep or anesthesia, raising questions about the characteristics of gamma oscillation during impaired consciousness and its role in conscious processing. Phase-amplitude modulation has been observed between slow wave activity (SWA, 0.5–4 Hz) and gamma oscillations during ketamine/xylazine anesthesia or sleep, showing increased gamma activity corresponding to the depolarized (ON) state of SWA. Here we divided gamma activity into its ON and OFF (hyperpolarized) state components based on the phase of SWA induced by ketamine/xylazine anesthesia and compared their power and synchrony with wake state levels in mice. We further investigated the state-dependent changes in both gamma power and synchrony across primary motor and primary somatosensory cortical regions and their interconnected thalamic regions throughout anesthesia and recovery. As observed previously, gamma power was as high as during wake specifically during the ON state of SWA. However, the synchrony of this gamma activity between somatosensory-motor cortical regions was significantly reduced compared to the baseline wake state. In addition, the somatosensory-motor cortical synchrony of gamma oscillations was reduced and restored in an anesthetic state-dependent manner, reflecting the changing depth of anesthesia. Our results provide evidence that during anesthesia changes in long-range information integration between cortical regions might be more critical for changes in consciousness than changes in local gamma oscillatory power. PMID:24379760

  20. Determination of S-wave slowness from a linear array of borehole receivers

    NASA Astrophysics Data System (ADS)

    Eisner, Leo; Fischer, Tomáš; Rutledge, James T.

    2009-01-01

    Locations of seismic events from a linear array of receivers may require determination of slowness vectors of arriving waves. In an isotropic medium, P waves are polarized along the slowness vector, which enables direct determination of backazimuth (i.e. azimuth to a source from a receiver) from P-wave polarization. In contrast, S waves usually have much larger signal-to-noise ratio than P waves, but are polarized in a plane perpendicular to their slowness vectors, which prevents direct determination of their backazimuth. We have developed a novel technique to determine the slowness vector of S waves detected in a linear array of receivers in an isotropic medium. We combine the S-wave polarization measurement with the derivative of the S-wave travel times along the array to obtain the full slowness vector and backazimuth. The proposed method allows one to determine direction to sources of seismic events from a single linear array of receivers, using only S waves. This technique is not affected by SV waves, which is shown by a test on a synthetic data set. We also test the method on two real microseismic data sets from hydraulic fracturing treatments and show that it outperforms the backazimuth determination from P waves and from horizontal polarization of S waves.

  1. Optimizing sleep/wake schedules in space: Sleep during chronic nocturnal sleep restriction with and without diurnal naps

    NASA Astrophysics Data System (ADS)

    Mollicone, Daniel J.; Van Dongen, Hans P. A.; Dinges, David F.

    2007-02-01

    Effective sleep/wake schedules for space operations must balance severe time constraints with allocating sufficient time for sleep in order to sustain high levels of neurobehavioral performance. Developing such schedules requires knowledge about the relationship between scheduled "time in bed" (TIB) and actual physiological sleep obtained. A ground-based laboratory study in N=93 healthy adult subjects was conducted to investigate physiological sleep obtained in a range of restricted sleep schedules. Eighteen different conditions with restricted nocturnal anchor sleep, with and without diurnal naps, were examined in a response surface mapping paradigm. Sleep efficiency was found to be a function of total TIB per 24 h regardless of how the sleep was divided among nocturnal anchor sleep and diurnal nap sleep periods. The amounts of sleep stages 1+2 and REM showed more complex relationships with the durations of the anchor and nap sleep periods, while slow-wave sleep was essentially preserved among the different conditions of the experiment. The results of the study indicated that when sleep was chronically restricted, sleep duration was largely unaffected by whether the sleep was placed nocturnally or split between nocturnal anchor sleep periods and daytime naps. Having thus assessed that split-sleep schedules are feasible in terms of obtaining physiological sleep, further research will reveal whether these schedules and the associated variations in the distribution of sleep stages may be advantageous in mitigating neurobehavioral performance impairment in the face of limited time for sleep.

  2. Effect of Daytime Exercise on Sleep Eeg and Subjective Sleep

    NASA Astrophysics Data System (ADS)

    Sasazawa, Y.; Kawada, T.; Kiryu, Y.

    1997-08-01

    This study was designed to assess the effects of daytime physical exercise on the quality of objective and subjective sleep by examining all-night sleep EEGs. The subjects were five male students, aged 19 to 20 years, who were in the habit of performing regular daytime exercise. The sleep polygraphic parameters in this study were sleep stage time as a percentage of total sleep time (%S1, %S2, %S(3+4), %SREM, %MT), time in bed (TIB), sleep time (ST), total sleep time (TST), sleep onset latency (SOL), waking from sleep, sleep efficiency, number of awakenings, number of stage shifts, number of spindles, and percentages of α and δ waves, all of which were determined by an automatic computer analysis system. The OSA questionnaire was used to investigate subjective sleep. The five scales of the OSA used were sleepiness, sleep maintenance, worry, integrated sleep feeling, and sleep initiation. Each sleep parameter was compared in the exercise and the non-exercise groups. Two-way analysis of variance was applied using subject factor and exercise factor. The main effect of the subject was significant in all parameters and the main effect of exercise in %S(3+4), SOL and sleep efficiency, among the objective sleep parameters. The main effects of the subject, except sleepiness, were significant, as was the main effect of exercise on sleep initiation, among the subjective sleep parameters. These findings suggest that daytime exercise shortened sleep latency and prolonged slow-wave sleep, and that the subjects fell asleep more easily on exercise days. There were also significant individual differences in both the objective and subjective sleep parameters.

  3. GABAB Receptors, Schizophrenia and Sleep Dysfunction

    PubMed Central

    Kantrowitz, Joshua; Citrome, Leslie; Javitt, Daniel

    2016-01-01

    Evidence for an intrinsic relationship between sleep, cognition and the symptomatic manifestations of schizophrenia is accumulating. This review presents evidence for the possible utility of GABAB receptor agonists for the treatment of subjective and objective sleep abnormalities related to schizophrenia. At the phenotypic level, sleep disturbance occurs in 16–30% of patients with schizophrenia and is related to reduced quality of life and poor coping skills. On the neurophysiological level, studies suggest that sleep deficits reflect a core component of schizophrenia. Specifically, slow-wave sleep deficits, which are inversely correlated with cognition scores, are seen. Moreover, sleep plays an increasingly well documented role in memory consolidation in schizophrenia. Correlations of slow-wave sleep deficits with impaired reaction time and declarative memory have also been reported. Thus, both behavioural insomnia and sleep architecture are critical therapeutic targets in patients with schizophrenia. However, long-term treatment with antipsychotics often results in residual sleep dysfunction and does not improve slow-wave sleep, and adjunctive GABAA receptor modulators, such as benzodiazepines and zolpidem, can impair sleep architecture and cognition in schizophrenia. GABAB receptor agonists have therapeutic potential in schizophrenia. These agents have minimal effect on rapid eye movement sleep while increasing slow-wave sleep. Preclinical associations with increased expression of genes related to slow-wave sleep production and circadian rhythm function have also been reported. GABAB receptor deficits result in a sustained hyperdopaminergic state and can be reversed by a GABAB receptor agonist. Genetic, postmortem and electrophysiological studies also associate GABAB receptors with schizophrenia. While studies thus far have not shown significant effects, prior focus on the use of GABAB receptor agonists has been on the positive symptoms of schizophrenia, with

  4. Enhancing the efficiency of slow-wave electron cyclotron masers with the tapered refractive index

    SciTech Connect

    Kong Lingbao; Hou Zhiling; Jing Jian; Jin Haibo; Du Chaohai

    2013-04-15

    The nonlinear analysis of slow-wave electron cyclotron masers (ECM) based on anomalous Doppler effect in a slab waveguide is presented. A method of tapered refractive index (TRI) is proposed to enhance the efficiency of slow-wave ECM. The numerical calculations show that the TRI method can significantly enhance the efficiency of slow-wave ECM with the frequency ranging from the microwave to terahertz band. The effect of beam velocity spread on the efficiency has also been studied. Although the velocity spread suppresses the efficiency significantly, a great enhancement of efficiency can still be introduced by the TRI method.

  5. Electrical slow waves in the mouse oviduct are dependent on extracellular and intracellular calcium sources

    PubMed Central

    Dixon, Rose Ellen; Britton, Fiona C.; Baker, Salah A.; Hennig, Grant W.; Rollings, Christina M.; Sanders, Kenton M.

    2011-01-01

    Spontaneous contractions of the myosalpinx are critical for oocyte transport along the oviduct. Slow waves, the electrical events that underlie myosalpinx contractions, are generated by a specialized network of pacemaker cells called oviduct interstitial cells of Cajal (ICC-OVI). The ionic basis of oviduct pacemaker activity is unknown. Intracellular recordings and Ca2+ imaging were performed to examine the role of extracellular and intracellular Ca2+ sources in slow wave generation. RT-PCR was performed to determine the transcriptional expression of Ca2+ channels. Molecular studies revealed most isoforms of L- and T-type calcium channels (Cav1.2,1.3,1.4,3.1,3.2,3.3) were expressed in myosalpinx. Reduction of extracellular Ca2+ concentration ([Ca2+]o) resulted in the abolition of slow waves and myosalpinx contractions without significantly affecting resting membrane potential (RMP). Spontaneous Ca2+ waves spread through ICC-OVI cells at a similar frequency to slow waves and were inhibited by reduced [Ca2+]o. Nifedipine depolarized RMP and inhibited slow waves; however, pacemaker activity returned when the membrane was repolarized with reduced extracellular K+ concentration ([K+]o). Ni2+ also depolarized RMP but failed to block slow waves. The importance of ryanodine and inositol 1,4,5 trisphosphate-sensitive stores were examined using ryanodine, tetracaine, caffeine, and 2-aminoethyl diphenylborinate. Results suggest that although both stores are involved in regulation of slow wave frequency, neither are exclusively essential. The sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) pump inhibitor cyclopiazonic acid inhibited pacemaker activity and Ca2+ waves suggesting that a functional SERCA pump is necessary for pacemaker activity. In conclusion, results from this study suggest that slow wave generation in the oviduct is voltage dependent, occurs in a membrane potential window, and is dependent on extracellular calcium and functional SERCA pumps. PMID:21881003

  6. Endothelial Function and Sleep: Associations of Flow-Mediated Dilation With Perceived Sleep Quality and Rapid Eye Movement (REM) Sleep

    PubMed Central

    Cooper, Denise C.; Ziegler, Michael G.; Milic, Milos S.; Ancoli-Israel, Sonia; Mills, Paul J.; Loredo, José S.; von Känel, Roland; Dimsdale, Joel E.

    2013-01-01

    Summary Endothelial function typically precedes clinical manifestations of cardiovascular disease and provides a potential mechanism for the associations observed between cardiovascular disease and sleep quality. This study examined how subjective and objective indicators of sleep quality relate to endothelial function, as measured by brachial artery flow-mediated dilation (FMD). In a clinical research center, 100 non-shift working adults (mean age: 36 years) completed FMD testing and the Pittsburgh Sleep Quality Index, along with a polysomnography assessment to obtain the following measures: slow wave sleep, percentage rapid eye movement (REM) sleep, REM sleep latency, total arousal index, total sleep time, wake after sleep onset, sleep efficiency, and apnea hypopnea index. Bivariate correlations and followup multiple regressions examined how FMD related to subjective (i.e., Pittsburgh Sleep Quality Index scores) and objective (i.e., polysomnography-derived) indicators of sleep quality. After FMD showed bivariate correlations with Pittsburgh Sleep Quality Index scores, percentage REM sleep, and REM latency, further examination with separate regression models indicated that these associations remained significant after adjustments for sex, age, race, hypertension, body mass index, apnea hypopnea index, smoking, and income (p's<0.05). Specifically, as FMD decreased, scores on the Pittsburgh Sleep Quality Index increased (indicating decreased subjective sleep quality) and percentage REM sleep decreased, while REM sleep latency increased (p's<0.05). Poorer subjective sleep quality and adverse changes in REM sleep were associated with diminished vasodilation, which could link sleep disturbances to cardiovascular disease. PMID:24033699

  7. Simulated Obstructive Sleep Apnea Increases P-Wave Duration and P-Wave Dispersion

    PubMed Central

    Wons, Annette M.; Rossi, Valentina; Bratton, Daniel J.; Schlatzer, Christian; Schwarz, Esther I.; Camen, Giovanni; Kohler, Malcolm

    2016-01-01

    Background A high P-wave duration and dispersion (Pd) have been reported to be a prognostic factor for the occurrence of paroxysmal atrial fibrillation (PAF), a condition linked to obstructive sleep apnea (OSA). We tested the hypothesis of whether a short-term increase of P-wave duration and Pd can be induced by respiratory manoeuvres simulating OSA in healthy subjects and in patients with PAF. Methods 12-lead-electrocardiography (ECG) was recorded continuously in 24 healthy subjects and 33 patients with PAF, while simulating obstructive apnea (Mueller manoeuvre, MM), obstructive hypopnea (inspiration through a threshold load, ITH), central apnea (AP), and during normal breathing (BL) in randomized order. The P-wave duration and Pd was calculated by using dedicated software for ECG-analysis. Results P-wave duration and Pd significantly increased during MM and ITH compared to BL in all subjects (+13.1ms and +13.8ms during MM; +11.7ms and +12.9ms during ITH; p<0.001 for all comparisons). In MM, the increase was larger in healthy subjects when compared to patients with PAF (p<0.05). Conclusion Intrathoracic pressure swings through simulated obstructive sleep apnea increase P-wave duration and Pd in healthy subjects and in patients with PAF. Our findings imply that intrathoracic pressure swings prolong the intra-atrial and inter-atrial conduction time and therefore may represent an independent trigger factor for the development for PAF. PMID:27071039

  8. Slow-Mode MHD Wave Penetration into a Coronal Null Point due to the Mode Transmission

    NASA Astrophysics Data System (ADS)

    Afanasyev, Andrey N.; Uralov, Arkadiy M.

    2016-05-01

    Recent observations of magnetohydrodynamic oscillations and waves in solar active regions revealed their close link to quasi-periodic pulsations in flaring light curves. The nature of that link has not yet been understood in detail. In our analytical modelling we investigate propagation of slow magnetoacoustic waves in a solar active region, taking into account wave refraction and transmission of the slow magnetoacoustic mode into the fast one. The wave propagation is analysed in the geometrical acoustics approximation. Special attention is paid to the penetration of waves in the vicinity of a magnetic null point. The modelling has shown that the interaction of slow magnetoacoustic waves with the magnetic reconnection site is possible due to the mode transmission at the equipartition level where the sound speed is equal to the Alfvén speed. The efficiency of the transmission is also calculated.

  9. Conventional, Bayesian, and Modified Prony's methods for characterizing fast and slow waves in equine cancellous bone

    PubMed Central

    Groopman, Amber M.; Katz, Jonathan I.; Holland, Mark R.; Fujita, Fuminori; Matsukawa, Mami; Mizuno, Katsunori; Wear, Keith A.; Miller, James G.

    2015-01-01

    Conventional, Bayesian, and the modified least-squares Prony's plus curve-fitting (MLSP + CF) methods were applied to data acquired using 1 MHz center frequency, broadband transducers on a single equine cancellous bone specimen that was systematically shortened from 11.8 mm down to 0.5 mm for a total of 24 sample thicknesses. Due to overlapping fast and slow waves, conventional analysis methods were restricted to data from sample thicknesses ranging from 11.8 mm to 6.0 mm. In contrast, Bayesian and MLSP + CF methods successfully separated fast and slow waves and provided reliable estimates of the ultrasonic properties of fast and slow waves for sample thicknesses ranging from 11.8 mm down to 3.5 mm. Comparisons of the three methods were carried out for phase velocity at the center frequency and the slope of the attenuation coefficient for the fast and slow waves. Good agreement among the three methods was also observed for average signal loss at the center frequency. The Bayesian and MLSP + CF approaches were able to separate the fast and slow waves and provide good estimates of the fast and slow wave properties even when the two wave modes overlapped in both time and frequency domains making conventional analysis methods unreliable. PMID:26328678

  10. Sleep in Children with Williams Syndrome

    PubMed Central

    Mason, Thornton B.A.; Arens, Raanan; Sharman, Jaclyn; Bintliff-Janisak, Brooke; Schultz, Brian; Walters, Arthur S.; Cater, Jacqueline R.; Kaplan, Paige; Pack, Allan I.

    2011-01-01

    Objective To analyze sleep in children with Williams Syndrome (WS) compared to normal healthy controls in order to determine whether particular sleep features are characteristic of WS, and to explore associations between disturbed sleep and behavior. Methods 35 children with genetically-confirmed WS and 35 matched controls underwent overnight polysomnography and performance testing in the Sleep Center at the Children’s Hospital of Philadelphia. Parents completed questionnaires regarding the subjects’ sleep and behavior. Results WS subjects had significantly different sleep than controls, with decreased sleep efficiency, increased respiratory-related arousals, and increased slow wave sleep on overnight polysomnography. WS subjects were also noted to have more difficulty falling asleep, with greater restlessness and more arousals from sleep than controls. 52% of WS subjects had features of attention deficit- hyperactivity disorder. Conclusions Children with WS had significantly different sleep than controls in our sample. These differences demonstrated in our study may reflect genetic influences on sleep. PMID:21940205

  11. Sleep and Breathing at High Altitude.

    PubMed

    Wickramasinghe, Himanshu; Anholm, James D.

    1999-01-01

    Sleep at high altitude is characterized by poor subjective quality, increased awakenings, frequent brief arousals, marked nocturnal hypoxemia, and periodic breathing. A change in sleep architecture with an increase in light sleep and decreasing slow-wave and REM sleep have been demonstrated. Periodic breathing with central apnea is almost universally seen amongst sojourners to high altitude, although it is far less common in long-standing high altitude dwellers. Hypobaric hypoxia in concert with periodic breathing appears to be the principal cause of sleep disruption at altitude. Increased sleep fragmentation accounts for the poor sleep quality and may account for some of the worsened daytime performance at high altitude. Hypoxic sleep disruption contributes to the symptoms of acute mountain sickness. Hypoxemia at high altitude is most severe during sleep. Acetazolamide improves sleep, AMS symptoms, and hypoxemia at high altitude. Low doses of a short acting benzodiazepine (temazepam) may also be useful in improving sleep in high altitude. PMID:11898114

  12. Sustained Sleep Fragmentation Induces Sleep Homeostasis in Mice

    PubMed Central

    Baud, Maxime O.; Magistretti, Pierre J.; Petit, Jean-Marie

    2015-01-01

    Study Objectives: Sleep fragmentation (SF) is an integral feature of sleep apnea and other prevalent sleep disorders. Although the effect of repetitive arousals on cognitive performance is well documented, the effects of long-term SF on electroencephalography (EEG) and molecular markers of sleep homeostasis remain poorly investigated. To address this question, we developed a mouse model of chronic SF and characterized its effect on EEG spectral frequencies and the expression of genes previously linked to sleep homeostasis including clock genes, heat shock proteins, and plasticity-related genes. Design: N/A. Setting: Animal sleep research laboratory. Participants : Sixty-six C57BL6/J adult mice. Interventions: Instrumental sleep disruption at a rate of 60/h during 14 days Measurements and Results: Locomotor activity and EEG were recorded during 14 days of SF followed by recovery for 2 days. Despite a dramatic number of arousals and decreased sleep bout duration, SF minimally reduced total quantity of sleep and did not significantly alter its circadian distribution. Spectral analysis during SF revealed a homeostatic drive for slow wave activity (SWA; 1–4 Hz) and other frequencies as well (4–40 Hz). Recordings during recovery revealed slow wave sleep consolidation and a transient rebound in SWA, and paradoxical sleep duration. The expression of selected genes was not induced following chronic SF. Conclusions: Chronic sleep fragmentation (SF) increased sleep pressure confirming that altered quality with preserved quantity triggers core sleep homeostasis mechanisms. However, it did not induce the expression of genes induced by sleep loss, suggesting that these molecular pathways are not sustainably activated in chronic diseases involving SF. Citation: Baud MO, Magistretti PJ, Petit JM. Sustained sleep fragmentation induces sleep homeostasis in mice. SLEEP 2015;38(4):567–579. PMID:25325477

  13. Serotonin neurons and sleep. I. Long term recordings of dorsal raphe discharge frequency and PGO waves.

    PubMed

    Lydic, R; McCarley, R W; Hobson, J A

    1987-10-01

    Brain stem transection studies suggest that pontine neurons play a key role in regulating the mammalian sleep cycle. The serotonin (5-HT) hypothesis originally postulated that pontine 5-HT containing neurons directly initiated and maintained synchronized or NREM sleep and "primed" rapid eye movement (REM) sleep. Contrary to the predictions of this hypothesis, single unit recordings from the serotonergic dorsal raphe nucleus (DRN) have uniformly shown that DRN discharge rate is positively correlated with behavioral arousal but negatively correlated with both the NREM and REM phases of sleep. These findings required revision of the original 5-HT hypothesis and suggested instead that DRN discharge may influence the maintenance of behavioral arousal and, by ceasing to discharge, may contribute to the generation of NREM and REM sleep. The purpose of this paper was to quantitatively assess the strength of the correlation between DRN discharge, REM sleep, and PGO waves following the experimental perturbations of the sleep cycle. Since forced locomotor activity is known to powerfully alter the timing of sleep and wakefulness, the present experiments used forced activity in an attempt to dissociate DRN discharge from the sleep cycle. It was hypothesized that such dissociations would suggest DRN discharge is not involved in sleep cycle regulation. Contrastingly, preserved correlations would support the hypothesis of a possible causal relationship between DRN discharge, PGO waves activity, and the timing of sleep and wakefulness. Extracellular recordings were obtained from single cells in the DRN of intact, undrugged cats across greater than 300 sleep cycles with durations ranging from about 8 to 80 mins. Forced activity significantly reduced the amount of time spent in wakefulness and increased the number but not the duration of REM sleep epochs. The results revealed that DRN discharge rate was altered as a function of sleep cycle duration. In no case, however, was forced

  14. Microfabrication of diamond-based slow-wave circuits for mm-wave and THz vacuum electronic sources

    NASA Astrophysics Data System (ADS)

    Lueck, M. R.; Malta, D. M.; Gilchrist, K. H.; Kory, C. L.; Mearini, G. T.; Dayton, J. A.

    2011-06-01

    Planar and helical slow-wave circuits for THz radiation sources have been made using novel microfabrication and assembly methods. A biplanar slow-wave circuit for a 650 GHz backward wave oscillator (BWO) was fabricated through the growth of diamond into high aspect ratio silicon molds and the selective metallization of the tops and sidewalls of 90 µm tall diamond features using lithographically created shadow masks. Helical slow-wave circuits for a 650 GHz BWO and a 95 GHz traveling wave tube were created through the patterning of trenches in thin film diamond, electroplating of gold half-helices, and high accuracy bonding of helix halves. The development of new techniques for the microfabrication of vacuum electronic components will help to facilitate compact and high-power sources for terahertz range radiation.

  15. Stick-slip at soft adhesive interfaces mediated by slow frictional waves.

    PubMed

    Viswanathan, Koushik; Sundaram, Narayan K; Chandrasekar, Srinivasan

    2016-06-28

    Stick-slip is a friction instability that governs diverse phenomena from squealing automobile brakes to earthquakes. At soft adhesive interfaces, this instability has long been attributed to Schallamach waves, which are a type of slow frictional wave. We use a contact configuration capable of isolating single wave events, coupled with high speed in situ imaging, to demonstrate the existence of two new stick-slip modes. It is shown that these modes also correspond to the passage of slow waves-separation pulse and slip pulse-with distinct nucleation and propagation characteristics. The slip pulse, characterized by a sharp stress front, propagates in the same direction as the Schallamach wave. In contrast, the separation pulse, involving local interface detachment and resembling a tensile neck, travels in exactly the opposite direction. A change in the stick-slip mode from the separation to the slip pulse is effected simply by increasing the normal force. Taken together, the three waves constitute all possible stick-slip modes in low-velocity sliding. The detailed observations enable us to present a phase diagram delineating the domains of occurrence of these waves. We suggest a direct analogy between the observed slow frictional waves and well known muscular locomotory waves in soft bodied organisms. Our work answers basic questions about adhesive mechanisms of frictional instabilities in natural and engineered systems, with broader implications for slow surface wave phenomena. PMID:27118236

  16. Propagation of Long-Wavelength Nonlinear Slow Sausage Waves in Stratified Magnetic Flux Tubes

    NASA Astrophysics Data System (ADS)

    Barbulescu, M.; Erdélyi, R.

    2016-05-01

    The propagation of nonlinear, long-wavelength, slow sausage waves in an expanding magnetic flux tube, embedded in a non-magnetic stratified environment, is discussed. The governing equation for surface waves, which is akin to the Leibovich-Roberts equation, is derived using the method of multiple scales. The solitary wave solution of the equation is obtained numerically. The results obtained are illustrative of a solitary wave whose properties are highly dependent on the degree of stratification.

  17. The Effects of Sleep Continuity Disruption on Positive Mood and Sleep Architecture in Healthy Adults

    PubMed Central

    Finan, Patrick H.; Quartana, Phillip J.; Smith, Michael T.

    2015-01-01

    Objective: The purpose of this study was to test an experimental model of the effects of sleep continuity disturbance on sleep architecture and positive mood in order to better understand the mechanisms linking insomnia and depression. Design: Participants were randomized to receive 3 consecutive nights of sleep continuity disruption via forced nocturnal awakenings (FA, n = 21), or one of two control conditions: restricted sleep opportunity (RSO, n = 17) or uninterrupted sleep (US, n = 24). Setting: The study was set in an inpatient clinical research suite. Participants: Healthy, good-sleeping men and women were included. Measurement and Results: Polysomnography was used to measure sleep architecture, and mood was assessed via self-report each day. Compared to restricted sleep opportunity controls, forced awakenings subjects had significantly less slow wave sleep (P < 0.05) after the first night of sleep deprivation, and significantly lower positive mood (P < 0.05) after the second night of sleep deprivation. The differential change in slow wave sleep statistically mediated the observed group differences in positive mood (P = 0.002). Conclusions: To our knowledge, this is the first human experimental study to demonstrate that, despite comparable reductions in total sleep time, partial sleep loss from sleep continuity disruption is more detrimental to positive mood than partial sleep loss from delaying bedtime, even when controlling for concomitant increases in negative mood. With these findings, we provide temporal evidence in support of a putative biologic mechanism (slow wave sleep deficit) that could help explain the strong comorbidity between insomnia and depression. Citation: Finan PH, Quartana PJ, Smith MT. The effects of sleep continuity disruption on positive mood and sleep architecture in healthy adults. SLEEP 2015;38(11):1735–1742. PMID:26085289

  18. Slow Waves in Fractures Filled with Viscous Fluid

    SciTech Connect

    Korneev, Valeri

    2008-01-08

    Stoneley guided waves in a fluid-filled fracture generally have larger amplitudes than other waves, and therefore, their properties need to be incorporated in more realistic models. In this study, a fracture is modeled as an infinite layer of viscous fluid bounded by two elastic half-spaces with identical parameters. For small fracture thickness, I obtain a simple dispersion equation for wave-propagation velocity. This velocity is much smaller than the velocity of a fluid wave in a Biot-type solution, in which fracture walls are assumed to be rigid. At seismic prospecting frequencies and realistic fracture thicknesses, the Stoneley guided wave has wavelengths on the order of several meters and an attenuation Q factor exceeding 10, which indicates the possibility of resonance excitation in fluid-bearing rocks. The velocity and attenuation of Stoneley guided waves are distinctly different at low frequencies for water and oil. The predominant role of fractures in fluid flow at field scales is supported by permeability data showing an increase of several orders of magnitude when compared to values obtained at laboratory scales. These data suggest that Stoneley guided waves should be taken into account in theories describing seismic wave propagation in fluid-saturated rocks.

  19. Linear analysis of a backward wave oscillator with triangular corrugated slow wave structure

    NASA Astrophysics Data System (ADS)

    Saber, Md. Ghulam; Sagor, Rakibul Hasan; Amin, Md. Ruhul

    2016-05-01

    In this work, a backward wave oscillator (BWO) with triangularly corrugated periodic metallic slow wave structure (TrCSWS) driven by an infinitely thin annular electron beam is studied using linear theory. The electron beam is assumed to be guided by a strong magnetic field. The triangular axial profile of the SWS is approximated by a Fourier series in order to apply the linear Rayleigh-Fourier (R-F) theory that has long been used in the theoretical analysis of BWOs with sinusoidally corrugated SWS (SCSWS). The dispersion equation for various beam parameters has been solved and the temporal growth rate (TGR) of the electromagnetic wave for the fundamental TM_{01} mode is calculated numerically. The TGR values for different beam parameters have been compared with those of the BWO with SCSWS, semi-circularly corrugated SWS (SCCSWS) and trapezoidally corrugated SWS (TCSWS). In order to compare the TGR values, the amplitude of corrugation of the TrCSWS is varied so that its dispersion curve of TM_{01} mode almost coincides with that of the SCSWS and TCSWS. The study reveals that the performance (in terms of TGR) of the proposed BWO with TrCSWS is comparable to that of other BWOs with SCSWS and TCSWS for the same set of beam parameters and it provides significantly better performance than SCCSWS. So, the proposed TrCSWS that can easily be constructed may replace SCSWS, SCCSWS or TCSWS as their viable alternative.

  20. Effects of a new slow release formulation of caffeine on EEG, psychomotor and cognitive functions in sleep-deprived subjects.

    PubMed

    Patat, Alain; Rosenzweig, Pierre; Enslen, Marc; Trocherie, Suzanne; Miget, Nathalie; Bozon, Marie-Christine; Allain, Hervé; Gandon, Jean-Marc

    2000-04-01

    Caffeine is a widely-consumed psychoactive substance whose stimulant effects on mood, attention and performance are largely recognised. The central nervous system pharmacodynamic profile of a single oral dose of a new slow release (SR) caffeine formulation (600 mg) was assessed in a randomised, double-blind, crossover, placebo-controlled study. Twelve young, health, male, sleep-deprived (for 36 h) subjects were studied using EEG and various measures of psychomotor and cognitive functions, including critical flicker fusion (CFF), choice reaction task (CRT), tracking, continuous performance task (CPT), Stroop test, body sway and subjective evaluation (Stanford Sleepiness Scale). Caffeine significantly ( < 0/05) antagonised the detrimental effects of sleep-deprivation on EEG (i.e. produced a significant decrease in delta and theta relative power and a significant increase in alpha and beta (12-40 Hz) relative power) and psychomotor performance (significant increase in speed of reaction on the CRT and Stroop tests, significant decrease in body sway, significant increase in accuracy of the CPT and significant reduction in subjective sedation) compared to placebo. The effect peaked 4 h after dosing and was maintained until the end of sleep deprivation (i.e. 24 h after dosing). In conclusion, the present results demonstrate that a single dose of caffeine SR possesses alerting effects which are able to reverse the deleterious effect of 36 h sleep deprivation for at least 24 h. Copyright 2000 John Wiley & Sons, Ltd. PMID:12404329

  1. Characterization of K-complexes and slow wave activity in a neural mass model.

    PubMed

    Weigenand, Arne; Schellenberger Costa, Michael; Ngo, Hong-Viet Victor; Claussen, Jens Christian; Martinetz, Thomas

    2014-11-01

    NREM sleep is characterized by two hallmarks, namely K-complexes (KCs) during sleep stage N2 and cortical slow oscillations (SOs) during sleep stage N3. While the underlying dynamics on the neuronal level is well known and can be easily measured, the resulting behavior on the macroscopic population level remains unclear. On the basis of an extended neural mass model of the cortex, we suggest a new interpretation of the mechanisms responsible for the generation of KCs and SOs. As the cortex transitions from wake to deep sleep, in our model it approaches an oscillatory regime via a Hopf bifurcation. Importantly, there is a canard phenomenon arising from a homoclinic bifurcation, whose orbit determines the shape of large amplitude SOs. A KC corresponds to a single excursion along the homoclinic orbit, while SOs are noise-driven oscillations around a stable focus. The model generates both time series and spectra that strikingly resemble real electroencephalogram data and points out possible differences between the different stages of natural sleep. PMID:25392991

  2. Characterization of K-Complexes and Slow Wave Activity in a Neural Mass Model

    PubMed Central

    Ngo, Hong-Viet Victor; Claussen, Jens Christian; Martinetz, Thomas

    2014-01-01

    NREM sleep is characterized by two hallmarks, namely K-complexes (KCs) during sleep stage N2 and cortical slow oscillations (SOs) during sleep stage N3. While the underlying dynamics on the neuronal level is well known and can be easily measured, the resulting behavior on the macroscopic population level remains unclear. On the basis of an extended neural mass model of the cortex, we suggest a new interpretation of the mechanisms responsible for the generation of KCs and SOs. As the cortex transitions from wake to deep sleep, in our model it approaches an oscillatory regime via a Hopf bifurcation. Importantly, there is a canard phenomenon arising from a homoclinic bifurcation, whose orbit determines the shape of large amplitude SOs. A KC corresponds to a single excursion along the homoclinic orbit, while SOs are noise-driven oscillations around a stable focus. The model generates both time series and spectra that strikingly resemble real electroencephalogram data and points out possible differences between the different stages of natural sleep. PMID:25392991

  3. Discrete-State Simulated Annealing For Traveling-Wave Tube Slow-Wave Circuit Optimization

    NASA Technical Reports Server (NTRS)

    Wilson, Jeffrey D.; Bulson, Brian A.; Kory, Carol L.; Williams, W. Dan (Technical Monitor)

    2001-01-01

    Algorithms based on the global optimization technique of simulated annealing (SA) have proven useful in designing traveling-wave tube (TWT) slow-wave circuits for high RF power efficiency. The characteristic of SA that enables it to determine a globally optimized solution is its ability to accept non-improving moves in a controlled manner. In the initial stages of the optimization, the algorithm moves freely through configuration space, accepting most of the proposed designs. This freedom of movement allows non-intuitive designs to be explored rather than restricting the optimization to local improvement upon the initial configuration. As the optimization proceeds, the rate of acceptance of non-improving moves is gradually reduced until the algorithm converges to the optimized solution. The rate at which the freedom of movement is decreased is known as the annealing or cooling schedule of the SA algorithm. The main disadvantage of SA is that there is not a rigorous theoretical foundation for determining the parameters of the cooling schedule. The choice of these parameters is highly problem dependent and the designer needs to experiment in order to determine values that will provide a good optimization in a reasonable amount of computational time. This experimentation can absorb a large amount of time especially when the algorithm is being applied to a new type of design. In order to eliminate this disadvantage, a variation of SA known as discrete-state simulated annealing (DSSA), was recently developed. DSSA provides the theoretical foundation for a generic cooling schedule which is problem independent, Results of similar quality to SA can be obtained, but without the extra computational time required to tune the cooling parameters. Two algorithm variations based on DSSA were developed and programmed into a Microsoft Excel spreadsheet graphical user interface (GUI) to the two-dimensional nonlinear multisignal helix traveling-wave amplifier analysis program TWA3

  4. Chronic hiccups and sleep.

    PubMed

    Arnulf, I; Boisteanu, D; Whitelaw, W A; Cabane, J; Garma, L; Derenne, J P

    1996-04-01

    To explore the effect of sleep on hiccups, we studied eight patients aged 20-81 years, all males with chronic hiccups lasting 7 days to 7 years, by means of overnight polysomnography. The incidence of new bouts of hiccups and the likelihood of hiccups being present were both highest in wakefulness and became progressively lower through stages I-IV of slow wave sleep (SWS) to rapid eye movement sleep (REMS). There was a significant tendency for hiccups to disappear at sleep onset and REMS onset. Of all 21 bouts of hiccups that were observed to stop, 10/21 did so during an apnea or hypopnea. Frequency of hiccups within a bout slowed progressively from wakefulness through the stages of SWS to REMS. For the whole group, mean frequency decreased significantly from wakefulness [(25.6 +/- 12.1), (mean +/- SD)] to sleep onset or stage I (22.3 +/- 12.2). Sleep latency was increased from 8 +/- 16.3 minutes when hiccups were absent to 16.35 +/- 19.9 minutes when it was present. Sleep efficiency was poor because of long waking periods, and there were deficiencies of both SWS and REMS. Hiccups themselves were not responsible for any arousals or awakenings. We conclude that neural mechanisms responsible for hiccups are strongly influenced by sleep state and that hiccups disrupt sleep onset but not established sleep. PMID:8723381

  5. Slowing and stopping of wave in dispersive metamaterial loaded helical guide.

    PubMed

    Sharma, Dushyant K; Pathak, Surya K

    2016-02-01

    We propose a dispersive metamaterial loaded helical waveguide (DMLHG) structure that supports slowing and stopping of Electromagnetic (EM) wave. Analytical and computational characterizations have been done to visualize various modal characteristics in detail using the Drude model as a dispersive parameter. It is observed that metamaterial insertion enhances helical guide slow wave behaviour and it supports both forward wave (FW) and backward wave (BW) as well as mode degeneracy. Obtained mode degeneracy mechanism leads to trapping of EM wave. The proposed guide structure provides a dynamic control of wave velocity by varying its physical parameters. Two possible structures are designed and simulated using CST Microwave Studio Software. The simulation results verify the presence of similar characteristics as observed in analytical study such as FW, BW, mode-degeneracy, but in slightly shifted frequency spectrum. PMID:26906840

  6. Giant amplification in degenerate band edge slow-wave structures interacting with an electron beam

    NASA Astrophysics Data System (ADS)

    Othman, Mohamed A. K.; Veysi, Mehdi; Figotin, Alexander; Capolino, Filippo

    2016-03-01

    We propose a new amplification regime based on a synchronous operation of four degenerate electromagnetic (EM) modes in a slow-wave structure and the electron beam, referred to as super synchronization. These four EM modes arise in a Fabry-Pérot cavity when degenerate band edge (DBE) condition is satisfied. The modes interact constructively with the electron beam resulting in superior amplification. In particular, much larger gains are achieved for smaller beam currents compared to conventional structures based on synchronization with only a single EM mode. We demonstrate giant gain scaling with respect to the length of the slow-wave structure compared to conventional Pierce type single mode traveling wave tube amplifiers. We construct a coupled transmission line model for a loaded waveguide slow-wave structure exhibiting a DBE, and investigate the phenomenon of giant gain via super synchronization using the Pierce model generalized to multimode interaction.

  7. The Role of Sleep in Changing Our Minds: A Psychologist's Discussion of Papers on Memory Reactivation and Consolidation in Sleep

    ERIC Educational Resources Information Center

    Cartwright, Rosalind D.

    2004-01-01

    The group of papers on memory reactivation and consolidation during sleep included in this volume represents cutting edge work in both animals and humans. They support that the two types of sleep serve different necessary functions. The role of slow wave sleep (SWS) is reactivation of the hippocampal-neocortical circuits activated during a waking…

  8. Update of sleep alterations in depression

    PubMed Central

    Medina, Andrés Barrera; Lechuga, DeboraYoaly Arana; Escandón, Oscar Sánchez; Moctezuma, Javier Velázquez

    2014-01-01

    Sleep disturbances in depression are up to 70%. Patients frequently have difficulty in falling asleep, frequent awakenings during the night and non-restorative sleep. Sleep abnormalities in depression are mainly characterized by increased rapid eye movement (REM) sleep and reduced slow wave sleep. Among the mechanisms of sleep disturbances in depression are hyperactivation of the hypothalamic-pituitary-adrenal axis, CLOCK gene polymorphism and primary sleep disorders. The habenula is a structure regulating the activities of monoaminergic neurons in the brain. The hyperactivation of the habenula has also been implicated, together with sleep disturbances, in depression. The presence of depression in primary sleep disorders is common. Sleep disturbances treatment include pharmacotherapy or Cognitive Behavioral Therapy. PMID:26483922

  9. Effects of thermal environment on sleep and circadian rhythm

    PubMed Central

    2012-01-01

    The thermal environment is one of the most important factors that can affect human sleep. The stereotypical effects of heat or cold exposure are increased wakefulness and decreased rapid eye movement sleep and slow wave sleep. These effects of the thermal environment on sleep stages are strongly linked to thermoregulation, which affects the mechanism regulating sleep. The effects on sleep stages also differ depending on the use of bedding and/or clothing. In semi-nude subjects, sleep stages are more affected by cold exposure than heat exposure. In real-life situations where bedding and clothing are used, heat exposure increases wakefulness and decreases slow wave sleep and rapid eye movement sleep. Humid heat exposure further increases thermal load during sleep and affects sleep stages and thermoregulation. On the other hand, cold exposure does not affect sleep stages, though the use of beddings and clothing during sleep is critical in supporting thermoregulation and sleep in cold exposure. However, cold exposure affects cardiac autonomic response during sleep without affecting sleep stages and subjective sensations. These results indicate that the impact of cold exposure may be greater than that of heat exposure in real-life situations; thus, further studies are warranted that consider the effect of cold exposure on sleep and other physiological parameters. PMID:22738673

  10. Noninvasive biomagnetic detection of intestinal slow wave dysrhythmias in chronic mesenteric ischemia

    PubMed Central

    Muszynski, N. D.; Cheng, L. K.; Bradshaw, L. A.; Naslund, T. C.; Richards, W. O.

    2015-01-01

    Chronic mesenteric ischemia (CMI) is a challenging clinical problem that is difficult to diagnose noninvasively. Diagnosis early in the disease process would enable life-saving early surgical intervention. Previous studies established that superconducting quantum interference device (SQUID) magnetometers detect the slow wave changes in the magnetoenterogram (MENG) noninvasively following induction of mesenteric ischemia in animal models. The purpose of this study was to assess functional physiological changes in the intestinal slow wave MENG of patients with chronic mesenteric ischemia. Pre- and postoperative studies were conducted on CMI patients using MENG and intraoperative recordings using invasive serosal electromyograms (EMG). Our preoperative MENG recordings showed that patients with CMI exhibited a significant decrease in intestinal slow wave frequency from 8.9 ± 0.3 cpm preprandial to 7.4 ± 0.1 cpm postprandial (P < 0.01) that was not observed in postoperative recordings (9.3 ± 0.2 cpm preprandial and 9.4 ± 0.4 cpm postprandial, P = 0.86). Intraoperative recording detected multiple frequencies from the ischemic portion of jejunum before revascularization, whereas normal serosal intestinal slow wave frequencies were observed after revascularization. The preoperative MENG data also showed signals with multiple frequencies suggestive of uncoupling and intestinal ischemia similar to intraoperative serosal EMG. Our results showed that multichannel MENG can identify intestinal slow wave dysrhythmias in CMI patients. PMID:25930082

  11. Metabolic consequences of sleep and sleep loss

    PubMed Central

    Van Cauter, Eve; Spiegel, Karine; Tasali, Esra; Leproult, Rachel

    2015-01-01

    Reduced sleep duration and quality appear to be endemic in modern society. Curtailment of the bedtime period to minimum tolerability is thought to be efficient and harmless by many. It has been known for several decades that sleep is a major modulator of hormonal release, glucose regulation and cardiovascular function. In particular, slow wave sleep (SWS), thought to be the most restorative sleep stage, is associated with decreased heart rate, blood pressure, sympathetic nervous activity and cerebral glucose utilization, compared with wakefulness. During SWS, the anabolic growth hormone is released while the stress hormone cortisol is inhibited. In recent years, laboratory and epidemiologic evidence have converged to indicate that sleep loss may be a novel risk factor for obesity and type 2 diabetes. The increased risk of obesity is possibly linked to the effect of sleep loss on hormones that play a major role in the central control of appetite and energy expenditure, such as leptin and ghrelin. Reduced leptin and increased ghrelin levels correlate with increases in subjective hunger when individuals are sleep restricted rather than well rested. Given the evidence, sleep curtailment appears to be an important, yet modifiable, risk factor for the metabolic syndrome, diabetes and obesity. The marked decrease in average sleep duration in the last 50 years coinciding with the increased prevalence of obesity, together with the observed adverse effects of recurrent partial sleep deprivation on metabolism and hormonal processes, may have important implications for public health. PMID:18929315

  12. Modelling changes in sleep timing and duration across the lifespan: Changes in circadian rhythmicity or sleep homeostasis?

    PubMed

    Skeldon, Anne C; Derks, Gianne; Dijk, Derk-Jan

    2016-08-01

    Sleep changes across the lifespan, with a delay in sleep timing and a reduction in slow wave sleep seen in adolescence, followed by further reductions in slow wave sleep but a gradual drift to earlier timing during healthy ageing. The mechanisms underlying changes in sleep timing are unclear: are they primarily related to changes in circadian processes, or to a reduction in the neural activity dependent build up of homeostatic sleep pressure during wake, or both? We review existing studies of age-related changes to sleep and explore how mathematical models can explain observed changes. Model simulations show that typical changes in sleep timing and duration, from adolesence to old age, can be understood in two ways: either as a consequence of a simultaneous reduction in the amplitude of the circadian wake-propensity rhythm and the neural activity dependent build-up of homeostatic sleep pressure during wake; or as a consequence of reduced homeostatic sleep pressure alone. A reduction in the homeostatic pressure also explains greater vulnerability of sleep to disruption and reduced daytime sleep-propensity in healthy ageing. This review highlights the important role of sleep homeostasis in sleep timing. It shows that the same phenotypic response may have multiple underlying causes, and identifies aspects of sleep to target to correct delayed sleep in adolescents and advanced sleep in later life. PMID:26545247

  13. Changes in Processing of Masked Stimuli across Early- and Late-Night Sleep: A Study on Behavior and Brain Potentials

    ERIC Educational Resources Information Center

    Verleger, Rolf; Schuknecht, Simon-Vitus; Jaskowski, Piotr; Wagner, Ullrich

    2008-01-01

    Sleep has proven to support the memory consolidation in many tasks including learning of perceptual skills. Explicit, conscious types of memory have been demonstrated to benefit particularly from slow-wave sleep (SWS), implicit, non-conscious types particularly from rapid eye movement (REM) sleep. By comparing the effects of early-night sleep,…

  14. T-Wave Alternans Patterns During Sleep in Healthy, Cardiac Disease and Sleep Apnea Patients

    PubMed Central

    Nemati, Shamim; Malhotra, Atul; Clifford, Gari D.

    2010-01-01

    Background T-Wave Alternans (TWA) activity is known to be a function of heart rate and condition, as well as perhaps physiological state. A recently published non-parametric non-stationary TWA analysis method has been shown to reject nonstationary noise accurately using phase randomized surrogates and has been shown to estimate TWA accurately. This new method was evaluated on multiple databases over a range of heart rates and in healthy subjects, cardiac patients, and obstructive sleep apnea (OSA) patients. We hypothesized that TWA would be lower than previously reported when measured with our new technique and that higher levels of TWA would be observed in OSA patients when compared to normals. Methods Five databases were analyzed: 1) Healthy subjects from PhysioNet’s Normal Sinus Rhythm Database (NSRDB), 2) Arrhythmia patients from PhysioNet’s Chronic Heart Failure Database (CHFDB) and 3) PhysioNet’s Sudden Cardiac Death Database (SCDDB), 4) OSA patients from PhysioNet’s MIT-BIH Polysomnographic Database (SLPDB), and 5) a private Sleep Apnea Database (SADB) of 85 subjects. TWA magnitudes were calculated for 7 heart rate decades [intervals of 10 beats per minute (BPM) between 40 and 110 BPM] for each database. The Mann-Whitney U-test and the two-sample Kolmogorov-Smirnov test were applied to test for significant differences between data from each database in each heart rate decade interval. Results In the healthy population TWA activity level tended to increase with heart rate. Moreover, there appeared to be an unexpected nadir in TWA activity around 60–70 BPM, and a small but significant rise in TWA above and below these heart rates. The rise in TWA at lower heart rates has not been previously reported to our knowledge. We also observed that TWA is unexpectedly lower in OSA patients and did not increase with heart rate. Conclusion Although the physiological mechanisms underlying our observations are unclear, there may be clinical implications for TWA

  15. Genotyping Sleep Disorders Patients

    PubMed Central

    Shadan, Farhad F.; Dawson, Arthur; Cronin, John W.; Jamil, Shazia M.; Grizas, Alexandra P.; Koziol, James A.; Kline, Lawrence E.

    2010-01-01

    Objective The genetic susceptibility factors underlying sleep disorders might help us predict prognoses and responses to treatment. Several candidate polymorphisms for sleep disorders have been proposed, but there has as yet inadequate replication or validation that the candidates may be useful in the clinical setting. Methods To assess the validity of several candidate associations, we obtained saliva deoxyribonucleic acid (DNA) samples and clinical information from 360 consenting research participants who were undergoing clinical polysomnograms. Ten single nucleotide polymorphisms (SNPs) were genotyped. These were thought to be related to depression, circadian sleep disorders, sleep apnea, restless legs syndrome (RLS), excessive sleepiness, or to slow waves in sleep. Results With multivariate generalized linear models, the association of TEF rs738499 with depressive symptoms was confirmed. Equivocal statistical evidence of association of rs1801260 (the C3111T SNP in the CLOCK gene) with morningness/eveningness and an association of Apolipoprotein E (APOE) rs429358 with the Epworth Sleepiness Scale (ESS) were obtained, but these associations were not strong enough to be of clinical value by themselves. Predicted association of SNPs with sleep apnea, RLS, and slow wave sleep were not confirmed. Conclusion The SNPs tested would not, by themselves, be of use for clinical genotyping in a sleep clinic. PMID:20396431

  16. Kinetic Simulation of Slow Magnetosonic Waves and Quasi-Periodic Upflows in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Ruan, Wenzhi; He, Jiansen; Zhang, Lei; Vocks, Christian; Marsch, Eckart; Tu, Chuanyi; Peter, Hardi; Wang, Linghua

    2016-07-01

    Quasi-periodic disturbances of emission-line parameters are frequently observed in the corona. These disturbances propagate upward along the magnetic field with speeds of ∼100 km s‑1. This phenomenon has been interpreted as evidence of the propagation of slow magnetosonic waves or has been argued to be a signature of intermittent outflows superposed on the background plasmas. Here we aim to present a new “wave + flow” model to interpret these observations. In our scenario, the oscillatory motion is a slow-mode wave, and the flow is associated with a beam created by the wave–particle interaction owing to Landau resonance. With the help of a kinetic model, we simulate the propagation of slow-mode waves and the generation of beam flows. We find that weak periodic beam flows can be generated by to Landau resonance in the solar corona, and the phase with the strongest blueward asymmetry is ahead of that with the strongest blueshift by about 1/4 period. We also find that the slow wave damps to the level of 1/e after the transit time of two wave periods, owing to Landau damping and Coulomb collisions in our simulation. This damping timescale is similar to that resulting from thermal conduction in the MHD regime. The beam flow is weakened/attenuated with increasing wave period and decreasing wave amplitude since Coulomb collisions become more and more dominant over the wave action. We suggest that this “wave + flow” kinetic model provides an alternative explanation for the observed quasi-periodic propagating perturbations in various parameters in the solar corona.

  17. Fast and slow flexural waves in a deviated borehole in homogeneous and layered anisotropic formations

    NASA Astrophysics Data System (ADS)

    He, Xiao; Hu, Hengshan; Guan, Wei

    2010-04-01

    Dipole acoustic fields in an arbitrarily deviated well penetrating a homogeneous as well as a stratified transversely isotropic formation are simulated using a 3-D finite-difference time-domain algorithm in cylindrical coordinates. The modelling results show that a dipole source can excite a fast- and a slow-flexural mode due to the shear wave anisotropy when the borehole is inclined with respect to the symmetry axis of transverse isotropy. Both flexural slownesses change with the wellbore deviation angle. The splitting of flexural modes is prominent in full wave arrays when the shear anisotropy is strong enough. It is revealed that the dipole orientation influences the relative amplitudes of the fast- and slow-flexural waves but it has no effect on their slownesses or phases. In a vertical well parallel to the symmetry axis, the two flexural waves degenerate and propagate at the same speed. The degenerated flexural wave travels approximately at the shear speed along the borehole wall except in a few formations. Our study shows, for example, that it is about 10 per cent slower than the shear wave in Mesaverde clayshale 5501. Even in that kind of formations, however, extraction of the fast- and slow-shear velocities from the flexural modes is still possible if the borehole deviation is large enough. To examine the effect of layering, we modelled the full waves in a formation with a sandwich. When the well is perpendicular to the layer interfaces, reflection is obvious and can be recognized. It becomes weaker or even invisible as the deviation angle increases, so it is difficult to detect a thin layer embedded in a formation directly from reflected waves. The sandwich can, instead, be recognized from the irregularity in the spectra of the full waveforms displayed versus depth. [Correction added after online publication 25th February 2009; the original spelling of `homogenous' in the title has been corrected to `homogeneous'.[

  18. Multi-channel wireless mapping of gastrointestinal serosal slow wave propagation

    PubMed Central

    Paskaranandavadivel, Niranchan; Wang, Rui; Sathar, Shameer; O’Grady, Gregory; Cheng, Leo K; Farajidavar, Aydin

    2015-01-01

    Background High-resolution (HR) extracellular mapping allows accurate profiling of normal and dysrhythmic slow wave patterns. A current limitation is that cables traverse the abdominal wall or a natural orifice, risking discomfort, dislodgement or infection. Wireless approaches offer advantages, but a multi-channel system is required, capable of recording slow waves and mapping propagation with high fidelity. Methods A novel multi-channel (n=7) wireless mapping system was developed and compared to a wired commercial system. Slow wave signals were recorded from the porcine gastric and intestinal serosa in-vivo. Signals were simultaneously acquired using both systems, and were filtered and processed to map activation wavefronts. For validation, the frequency and amplitude of detected events were compared, together with the speed and direction of mapped wavefronts. Key Results The wireless device achieved comparable signal quality to the reference device, and slow wave frequencies were identical. Amplitudes of the acquired gastric and intestinal slow wave signals were consistent between the devices. During normal propagation, spatiotemporal mapping remained accurate in the wireless system, however, during ectopic dysrhythmic pacemaking, the lower sampling resolution of the wireless device led to reduced accuracy in spatiotemporal mapping. Conclusions and Inferences A novel multichannel wireless device is presented for mapping slow wave activity. The device achieved high quality signals, and has the potential to facilitate chronic monitoring studies and clinical translation of spatiotemporal mapping. The current implementation may be applied to detect normal patterns and dysrhythmia onset, but HR mapping with finely spaced arrays currently remains necessary to accurately define dysrhythmic patterns. PMID:25599978

  19. Pediatric sleep apnea

    MedlinePlus

    Sleep apnea - pediatric; Apnea - pediatric sleep apnea syndrome; Sleep-disordered breathing - pediatric ... Untreated pediatric sleep apnea may lead to: High blood pressure Heart or lung problems Slow growth and development

  20. Enhanced four-wave mixing in graphene-silicon slow-light photonic crystal waveguides

    SciTech Connect

    Zhou, Hao E-mail: tg2342@columbia.edu; Gu, Tingyi E-mail: tg2342@columbia.edu McMillan, James F.; Wong, Chee Wei E-mail: tg2342@columbia.edu; Petrone, Nicholas; Zande, Arend van der; Hone, James C.; Yu, Mingbin; Lo, Guoqiang; Kwong, Dim-Lee; Feng, Guoying; Zhou, Shouhuan

    2014-09-01

    We demonstrate the enhanced four-wave mixing of monolayer graphene on slow-light silicon photonic crystal waveguides. 200-μm interaction length, a four-wave mixing conversion efficiency of −23 dB is achieved in the graphene-silicon slow-light hybrid, with an enhanced 3-dB conversion bandwidth of about 17 nm. Our measurements match well with nonlinear coupled-mode theory simulations based on the measured waveguide dispersion, and provide an effective way for all-optical signal processing in chip-scale integrated optics.

  1. Slow Magnetosonic Waves Generated in the Plasmasphere by Ionospheric Terminator Motion

    NASA Astrophysics Data System (ADS)

    Leonovich, A. S.; Kozlov, D. A.

    2012-11-01

    A problem of the structure and spectrum of slow magnetosonic waves in a dipole plasmasphere is solved. The numerical solutions are found to the problem, for a distribution of the plasma parameters typical of the Earth's plasmasphere. The solutions allow us to treat the total electronic content oscillations registered above Japan as oscillations of one of the first harmonics of standing slow magnetosonic (SMS) waves. The results of numerical calculations of total electron content (TEC) oscillation amplitude are compared to the observations of the TEC oscillations and are shown to be in a good agreement with them.

  2. Shock Formation and Energy Dissipation of Slow Magnetosonic Waves in Coronal Plumes

    NASA Technical Reports Server (NTRS)

    Cuntz, M.; Suess, S. T.

    2003-01-01

    We study the shock formation and energy dissipation of slow magnetosonic waves in coronal plumes. The wave parameters and the spreading function of the plumes as well as the base magnetic field strength are given by empirical constraints mostly from SOHO/UVCS. Our models show that shock formation occurs at low coronal heights, i.e., within 1.3 bun, depending on the model parameters. In addition, following analytical estimates, we show that scale height of energy dissipation by the shocks ranges between 0.15 and 0.45 Rsun. This implies that shock heating by slow magnetosonic waves is relevant at most heights, even though this type of waves is apparently not a solely operating energy supply mechanism.

  3. Estimation of Delta Wave by Mutual Information of Heartbeat During Sleep

    NASA Astrophysics Data System (ADS)

    Kurihara, Yosuke; Watanabe, Kajiro; Kobayashi, Kazuyuki; Tanaka, Hiroshi

    The quality of sleep is evaluated based on the sleep stages judged by R-K method or the manual of American Academy of Sleep Medicine. The brainwaves, eye movements, and chin EMG of sleeping subjects are used for the judgment. These methods above, however, require some electrodes to be attached to the head and the face to obtain the brainwaves, eye movements, and chin EMG, thus making the measurements troublesome to be held on a daily basis. If non-invasive measurements of brainwaves, eye movements, and chin EMG are feasible, or their equivalent data can be estimated through other bio-signals, the monitoring of the quality of daily sleeps, which influences the health condition, will be easy. In this paper, we discuss the appearance rate of delta wave occurrences, which is deeply related with the depth of sleep, can be estimated based on the average amount of mutual information calculated by pulse wave signals and body movements measured non-invasively by the pneumatic method. As a result, the root mean square error between the appearance rate of delta wave occurrences measured with a polysomnography and the estimated delta pulse was 14.93%.

  4. Slow wave structures using twisted waveguides for charged particle applications

    SciTech Connect

    Kang, Yoon W.; Fathy, Aly E.; Wilson, Joshua L.

    2012-12-11

    A rapidly twisted electromagnetic accelerating structure includes a waveguide body having a central axis, one or more helical channels defined by the body and disposed around a substantially linear central axial channel, with central portions of the helical channels merging with the linear central axial channel. The structure propagates electromagnetic waves in the helical channels which support particle beam acceleration in the central axial channel at a phase velocity equal to or slower than the speed of light in free space. Since there is no variation in the shape of the transversal cross-section along the axis of the structure, inexpensive mechanical fabrication processes can be used to form the structure, such as extrusion, casting or injection molding. Also, because the field and frequency of the resonant mode depend on the whole structure rather than on dimensional tolerances of individual cells, no tuning of individual cells is needed. Accordingly, the overall operating frequency may be varied with a tuning/phase shifting device located outside the resonant waveguide structure.

  5. SDO/AIA Observation and Modeling of Flare-excited Slow Waves in Hot Coronal Loops

    NASA Astrophysics Data System (ADS)

    Wang, T.; Ofman, L.; Provornikova, E.; Sun, X.; Davila, J. M.

    2014-12-01

    The flare-excited standing slow waves were first detected by SOHO/SUMER as Doppler shift oscillations in hot (>6 MK) coronal loops. It has been suggested that they are excited by small or micro- flares at one loop's footpoint. However, the detailed excitation mechanism remains unclear. In this study, we report an oscillation event observed by SDO/AIA in the 131 channel. The intensity disturbances excited by a C-class flare propagated back and forth along a hot loop for about two period with a strong damping. From the measured oscillation period and loop length, we estimate the wave phase speed to be about 410 km/s. Using a regularized DEM analysis we determine the loop temperature and electron density evolution and find that the loop plasma is heated to a temperature of 8-12 MK with a mean about 9 MK. These measurements support the interpretation as slow magnetoacousic waves. Magnetic field extrapolation suggests that the flare is triggered by slipping and null-point-type reconnections in a fan-spine magnetic topology, and the injected (or impulsively evaporated) hot plasmas flowing along the large spine field lines form the oscillating hot loops. To understand why the propagating waves but not the standing waves as observed previously are excited in this event, we preform simulations using a 3D MHD model based on the observed magnetic configuration including full energy equation. Our simulations indicate that the nature of loop temperature structure is critical for the excitation of whether propagating or standing waves in a hot loop. Our result demonstrates that the slow waves may be used for heating diagnostics of coronal loops with coronal seismology. We also discuss the application of coronal seismology for estimating the average magnetic field strength in the hot loop based on the observed slow waves.

  6. Cut-off period for slow magnetoacoustic waves in coronal plasma structures

    NASA Astrophysics Data System (ADS)

    Afanasyev, A. N.; Nakariakov, V. M.

    2015-10-01

    Context. There is abundant observational evidence of longitudinal compressive waves in plasma structures of the solar corona, which are confidently interpreted in terms of slow magnetoacoustic waves. The uses of coronal slow waves in plasma diagnostics, as well as analysis of their possible contribution to coronal heating and the solar wind acceleration, require detailed theoretical modelling. Aims: We investigate the effects of obliqueness, magnetic field, and non-uniformity of the medium on the evolution of long-wavelength slow magnetoacoustic waves guided by field-aligned plasma non-uniformities, also called tube waves. Special attention is paid to the cut-off effect due to the gravity stratification of the coronal plasma. Methods: We study the behaviour of linear tube waves in a vertical untwisted straight field-aligned isothermal plasma cylinder. We apply the thin flux tube approximation, taking into account effects of stratification caused by gravity. The dispersion due to the finite radius of the flux tube is neglected. We analyse the behaviour of the cut-off period for an exponentially divergent magnetic flux tube filled in with a stratified plasma. The results obtained are compared with the known cases of the constant Alfven speed and the pure acoustic wave. Results: We derive the wave equation for tube waves and reduce it to the form of the Klein-Gordon equation with varying coefficients, which explicitly contains the cut-off frequency. The cut-off period is found to vary with height, decreasing significantly in the low-beta plasma and in the plasma with the beta of the order of unity. The depressions in the cut-off period profiles can affect the propagation of longitudinal waves along coronal plasma structures towards the higher corona and can form coronal resonators.

  7. Possible influence of AMPD1 on cholinergic neurotransmission and sleep.

    PubMed

    Buyse, Bertien; Van Damme, Philip; Belge, Catharina; Testelmans, Dries

    2016-02-01

    It is known that adenosine excess due to monophosphate deaminase deficiency (AMPD1) can be linked to muscle problems. Recently, Perumal et al., 2014 reported a first case of possible impact of AMPD1 on sleep, REM sleep and cholinergic neurotransmission. We report a second patient with similar sleep complaints: long sleep duration with residual daytime sleepiness and a need to sleep after exercise. On polysomnography we observed a long sleep duration, with high sleep efficiency and a SOREMP; on MSLT a shortened sleep latency and 4 SOREMPS were observed. Frequency power spectral heart rate analysis during slow wave sleep, REM sleep and wakefulness revealed an increased parasympathetic tone. In conclusion, AMPD1 could have a profound influence on cholinergic neurotransmission and sleep; further studies are mandatory. PMID:26439223

  8. Preliminary study of slow and fast ultrasonic waves using MR images of trabecular bone phantom

    NASA Astrophysics Data System (ADS)

    Solis-Najera, S. E.; Neria-Pérez, J. A.; Medina, L.; Garipov, R.; Rodríguez, A. O.

    2014-11-01

    Cancellous bone is a complex tissue that performs physiological and biomechanical functions in all vertebrates. It is made up of trabeculae that, from a simplified structural viewpoint, can be considered as plates and beams in a hyperstatic structure that change with time leading to osteoporosis. Several methods has been developed to study the trabecular bone microstructure among them is the Biot's model which predicts the existence of two longitudinal waves in porous media; the slow and the fast waves, that can be related to porosity of the media. This paper is focused on the experimental detection of the two Biot's waves of a trabecular bone phantom, consisting of a trabecular network of inorganic hydroxyapatite. Experimental measurements of both waves were performed using through transmission ultrasound. Results had shown clearly that the propagation of two waves propagation is transversal to the trabecular alignment. Otherwise the waves are overlapped and a single wave seems to be propagated. To validate these results, magnetic resonance images were acquired to assess the trabecular direction, and to assure that the pulses correspond to the slow and fast waves. This approach offers a methodology for non-invasive studies of trabecular bones.

  9. Preliminary study of slow and fast ultrasonic waves using MR images of trabecular bone phantom

    SciTech Connect

    Solis-Najera, S. E. E-mail: angel.perez@ciencias.unam.mx Neria-Pérez, J. A. E-mail: angel.perez@ciencias.unam.mx Medina, L. E-mail: angel.perez@ciencias.unam.mx; Garipov, R.; Rodríguez, A. O.

    2014-11-07

    Cancellous bone is a complex tissue that performs physiological and biomechanical functions in all vertebrates. It is made up of trabeculae that, from a simplified structural viewpoint, can be considered as plates and beams in a hyperstatic structure that change with time leading to osteoporosis. Several methods has been developed to study the trabecular bone microstructure among them is the Biot’s model which predicts the existence of two longitudinal waves in porous media; the slow and the fast waves, that can be related to porosity of the media. This paper is focused on the experimental detection of the two Biot’s waves of a trabecular bone phantom, consisting of a trabecular network of inorganic hydroxyapatite. Experimental measurements of both waves were performed using through transmission ultrasound. Results had shown clearly that the propagation of two waves propagation is transversal to the trabecular alignment. Otherwise the waves are overlapped and a single wave seems to be propagated. To validate these results, magnetic resonance images were acquired to assess the trabecular direction, and to assure that the pulses correspond to the slow and fast waves. This approach offers a methodology for non-invasive studies of trabecular bones.

  10. Effects of body mass index on gastric slow wave: a magnetogastrographic study.

    PubMed

    Somarajan, S; Cassilly, S; Obioha, C; Richards, W O; Bradshaw, L A

    2014-02-01

    We measured gastric slow wave activity simultaneously with magnetogastrogram (MGG), mucosal electromyogram (EMG) and electrogastrogram (EGG) in human subjects with varying body mass index (BMI) before and after a meal. In order to investigate the effect of BMI on gastric slow wave parameters, each subject's BMI was calculated and divided into two groups: subjects with BMI ≤ 27 and BMI > 27. Signals were processed with Fourier spectral analysis and second-order blind identification (SOBI) techniques. Our results showed that increased BMI does not affect signal characteristics such as frequency and amplitude of EMG and MGG. Comparison of the postprandial EGG power, on the other hand, showed a statistically significant reduction in subjects with BMI > 27 compared with BMI ≤ 27. In addition to the frequency and amplitude, the use of SOBI-computed propagation maps from MGG data allowed us to visualize the propagating slow wave and compute the propagation velocity in both BMI groups. No significant change in velocity with increasing BMI or meal was observed in our study. In conclusion, multichannel MGG provides an assessment of frequency, amplitude and propagation velocity of the slow wave in subjects with differing BMI categories and was observed to be independent of BMI. PMID:24398454

  11. Standing Slow-Mode Waves in Hot Coronal Loops: Observations, Modeling, and Coronal Seismology

    NASA Astrophysics Data System (ADS)

    Wang, Tongjiang

    2011-07-01

    Strongly damped Doppler shift oscillations are observed frequently associated with flarelike events in hot coronal loops. In this paper, a review of the observed properties and the theoretical modeling is presented. Statistical measurements of physical parameters (period, decay time, and amplitude) have been obtained based on a large number of events observed by SOHO/SUMER and Yohkoh/BCS. Several pieces of evidence are found to support their interpretation in terms of the fundamental standing longitudinal slow mode. The high excitation rate of these oscillations in small- or micro-flares suggest that the slow mode waves are a natural response of the coronal plasma to impulsive heating in closed magnetic structure. The strong damping and the rapid excitation of the observed waves are two major aspects of the waves that are poorly understood, and are the main subject of theoretical modelling. The slow waves are found mainly damped by thermal conduction and viscosity in hot coronal loops. The mode coupling seems to play an important role in rapid excitation of the standing slow mode. Several seismology applications such as determination of the magnetic field, temperature, and density in coronal loops are demonstrated. Further, some open issues are discussed.

  12. Social Exclusion in Middle Childhood: Rejection Events, Slow-wave Neural Activity and Ostracism Distress

    PubMed Central

    Crowley, Michael J.; Wu, Jia; Molfese, Peter J.; Mayes, Linda C.

    2010-01-01

    This study examined neural activity with event-related potentials (ERPs) in middle childhood during a computer-simulated ball-toss game, Cyberball. Experiencing fair play initially, children were ultimately excluded by the other players. We focused specifically on “not my turn” events within fair play and rejection events within social exclusion. Dense-array ERPs revealed that rejection events are perceived rapidly. Condition differences (“not my turn” vs. rejection) were evident in a posterior ERP peaking at 420 ms consistent, with a larger P3 effect for rejection events indicating that in middle childhood rejection events are differentiated in < 500 ms. Condition differences were evident for slow-wave activity (500–900 ms) in the medial frontal cortical region and the posterior occipital-parietal region, with rejection events more negative frontally and more positive posteriorly. Distress from the rejection experience was associated with a more negative frontal slow wave and a larger late positive slow wave, but only for rejection events. Source modeling with Geosouce software suggested that slow wave neural activity in cortical regions previously identified in functional imaging studies of ostracism, including subgenual cortex, ventral anterior cingulate cortex and insula was greater for rejection events vs. “not my turn” events. PMID:20628967

  13. Compressible turbulence with slow-mode waves observed in the bursty bulk flow of plasma sheet

    NASA Astrophysics Data System (ADS)

    Wang, Tieyan; Cao, Jinbin; Fu, Huishan; Meng, Xuejie; Dunlop, M.

    2016-03-01

    In this paper, we report the evidence of compressible turbulence with slow-mode waves in a bursty bulk flow of plasma sheet. This compressible turbulence is characterized by a multiscale (1-60 s) anticorrelation between plasma density and magnetic field strength. Besides, the magnetic compressibility spectrum stays nearly constant at all the measured frequencies. Furthermore, the turbulence energy distributions are anisotropic with k⊥ > k//, and the dispersion relation is consistent with slow-mode prediction. The fluctuations of density and magnetic field have similar double slope spectrum and kurtosis. These results suggest that the slow waves are involved in the intermittent turbulence cascade from MHD to ion kinetic scales, which may have significant implications for the energy transfer in the plasma sheet.

  14. Habitual sleep length and patterns of recovery sleep after 24 hour and 36 hour sleep deprivation.

    PubMed

    Benoit, O; Foret, J; Bouard, G; Merle, B; Landau, J; Marc, M E

    1980-12-01

    Five long sleepers (LS) and 5 short sleepers (SS) were selected from 310 medical students. Nine regular sleepers (RS) were used as a control. The sleep was recorded during 3 reference nights, one recovery night after a 36 h sleep deprivation (R2), one morning sleep after a 24 h sleep deprivation (D1) and the night following D1(R1). According to previous data slow wave sleep (SWS) amounts were the same in the 3 groups while stage 2 and paradoxical sleep (PS) amounts increased with the sleep duration. The hourly distribution of intervening wakefulness and SWS were similar for all groups. When compared to RS or SS the hourly distribution in LS of PS was lower until the sixth hour. As a function of experimental conditions, sleep patterns of LS were the most affected. In R2 the sleep of LS more closely resembled that of RS or SS than in reference nights, while in R1 LS' sleep was the most disturbed. Morning sleep durations were very similar for all groups, but in LS intervening wakefulness was increased and PS was decreased when compared to RS and SS. Negative correlations (Spearman rank test) were found between the morning increase of body temperature after a sleep-deprived night and both TST and PS durations. In all recorded sleep periods, SWS amounts were positively correlated with prior wakefulness duration and the PS amount with TST. PMID:6160990

  15. Beam-plasma amplifiers based on nonhomogeneous plasma-cavity slow-wave structure

    SciTech Connect

    Perevodchikov, V.I.; Mitin, L.A.; Shapiro, A.L.; Zavjalov, M.A.

    1995-11-01

    The investigation of interaction of E-beam with hybrid waves of nonhomogeneous plasma-cavity slow-wave structure have been carried out. It`s shown that depression of external magnetic field at out-put part of plasma-cavity structure may be used for decreasing of phase velocity of active waves and phase space synchronization ones with space charge fields, induced in plasma. This mode of operation of plasma TWT was calculated. The investigations carried out theoretically has been supported by experiments with plasma TWT.

  16. Simultaneous realization of negative group velocity, fast and slow acoustic waves in a metamaterial

    NASA Astrophysics Data System (ADS)

    Li, Xiao-juan; Xue, Cheng; Fan, Li; Zhang, Shu-yi; Chen, Zhe; Ding, Jin; Zhang, Hui

    2016-06-01

    An acoustic metamaterial is designed based on a simple and compact structure of one string of side pipes arranged along a waveguide, in which diverse group velocities are achieved. Owing to Fabry-Perot resonance of the side pipes, a negative phase time is achieved, and thus, acoustic waves transmitting with negative group velocities are produced near the resonant frequency. In addition, both fast and slow acoustic waves are also observed in the vicinity of the resonance frequency. The extraordinary group velocities can be explained based on spectral rephasing induced by anomalous dispersion on the analogy of Lorentz dispersion in electromagnetic waves.

  17. Calculation of coupling to slow and fast waves in the LHRF from phased waveguide arrays

    SciTech Connect

    Pinsker, R.I.; Duvall, R.E.; Fortgang, C.M.; Colestock, P.L.

    1986-04-01

    A previously reported algorithm for solving the problem of coupling electromagnetic energy in the LHRF from a phased array of identical rectangular waveguides to a plane-stratified, magnetized cold plasma is numerically implemented. The resulting computer codes are sufficiently general to allow for an arbitrary number of waveguides with finite dimensions in both poloidal and toroidal directions, and are thus capable of computing coupling to both slow and fast waves in the plasma. Some of the details of the implementation and the extension of the algorithm to allow study of the Fourier spectrum of slow and fast waves launched by the array are discussed. Good agreement is found with previously reported, less general work for the slow wave launching case. The effect of phasing multirow arrays in the poloidal direction is studied, and an asymmetry between phasing 'up' and 'down' is found that persists in the case where the plasma adjacent to the array is uniform. A 4 x 3 array designed to launch fast waves of high phase velocity is studied. By using the optimal poloidal phasing, low reflection coefficients (absolute value of R/sup 2/ less than or equal to 20%) are found under some not unrealistic edge plasma conditions, but most of the input power is trapped in the outermost layer of the plasma. Implications of our results for fast wave current drive experiments are discussed.

  18. Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, James A., Jr.

    1997-01-01

    Recently, a method has been established to accurately calculate cold-test data for helical slow-wave structures using the three-dimensional electromagnetic computer code, MAFIA. Cold-test parameters have been calculated for several helical traveling-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment. The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits. The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making it possible, for the first time, to design a complete TWT via computer simulation.

  19. Effect of Helical Slow-Wave Circuit Variations on TWT Cold-Test Characteristics

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, James A., Jr.

    1997-01-01

    Recent advances in the state of the art of computer modeling offer the possibility for the first time to evaluate the effect that slow-wave structure parameter variations, such as manufacturing tolerances, have on the cold-test characteristics of helical traveling-wave tubes (TWT's). This will enable manufacturers to determine the cost effectiveness of controlling the dimensions of the component parts of the TWT, which is almost impossible to do experimentally without building a large number of tubes and controlling several parameters simultaneously. The computer code MAFIA is used in this analysis to determine the effect on dispersion and on-axis interaction impedance of several helical slow-wave circuit parameter variations, including thickness and relative dielectric constant of the support rods, tape width, and height of the metallized films deposited on the dielectric rods. Previous computer analyses required so many approximations that accurate determinations of the effect of many relevant dimensions on tube performance were practically impossible.

  20. Fast and slow magnetosonic waves in two-dimensional spin-1/2 quantum plasma

    SciTech Connect

    Mushtaq, A.; Vladimirov, S. V.

    2010-10-15

    Using the spin-1/2 resistive quantum magnetohydrodynamics model, linear and nonlinear relations for slow and fast magnetosonic modes are derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. The plasma resistivity is shown to play a role of dissipation in the system. With the aid of tanh method the traveling wave solution of Kadomstev-Petviashvili-Burgers is obtained. The solution shows a general shock wave profile superposed by a perturbative solitary-wave contribution. The dynamics of fast and slow magnetosonic shock and soliton, respectively, in the presence and absence of dissipation is investigated with respect to electron spin magnetization, quantum diffraction, and plasma statistic. It is found that results obtained from the spin quantum plasmas differ significantly from the nonspin quantum plasmas. The relevance of the present work to dense astrophysical plasmas such as pulsar magnetosphere is pointed out.

  1. Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, J. A., Jr.

    1998-01-01

    Recently, a method has been established to accurately calculate cold-test data for helical slow-wave structures using the three-dimensional (3-D) electromagnetic computer code, MAFIA. Cold-test parameters have been calculated for several helical traveling-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment. The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits. The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making it possible, for the first time, to design a complete TWT via computer simulation.

  2. Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, James A., Jr.

    1998-01-01

    Recently, a method has been established to accurately calculate cold-test data for helical slow-wave structures using the three-dimensional (3-D) electromagnetic computer code, MAxwell's equations by the Finite Integration Algorithm (MAFIA). Cold-test parameters have been calculated for several helical traveLing-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment. The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits. The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making It possible, for the first time, to design complete TWT via computer simulation.

  3. Numerical calculation of electromagnetic eigenfields and dispersion relations for slow-wave device simulation

    SciTech Connect

    Oslake, J.M.; Verboncoeur, J.P.; Birdsall, C.K.

    1996-12-31

    Slow-wave structures support microwave amplification via electromagnetic coupling with an injected electron beam. Critical in the design of such devices is the dependence of the dispersion relation on the geometry of the guiding structure. The dispersion relation provides phase and group velocities, and the fields provide the impedance as seen by the beam. To this end, a computer model is developed which first numerically solves a wave equation in finite difference form subject to boundary conditions periodic in z and conducting elsewhere. For decades, the desired dispersion and impedance have been obtained experimentally from cold tests (no beam) on slow-wave structures by varying structure dimensions. However, the numerical approach condenses this process to a few minutes of simulation.

  4. Effect of Helical Slow-Wave Circuit Variations on TWT Cold-Test Characteristics

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, J. A., Jr.

    1998-01-01

    Recent advances in the state of the art of computer modeling offer the possibility for the first time to evaluate the effect that slow-wave structure parameter variations, such as manufacturing tolerances, have on the cold-test characteristics of helical traveling-wave tubes (TWT's). This will enable manufacturers to determine the cost effectiveness of controlling the dimensions of the component parts of the TWT, which is almost impossible to do experimentally without building a large number of tubes and controlling several parameters simultaneously. The computer code MAFIA is used in this analysis to determine the effect on dispersion and on-axis interaction impedance of several helical slow-wave circuit parameter variations, including thickness and relative dielectric constant of the support rods, tape width, and height of the metallized films deposited on the dielectric rods. Previous computer analyzes required so many approximations that accurate determinations of the effect of many relevant dimensions on tube performance were practically impossible.

  5. Sleeping worries away or worrying away sleep? Physiological evidence on sleep-emotion interactions.

    PubMed

    Talamini, Lucia M; Bringmann, Laura F; de Boer, Marieke; Hofman, Winni F

    2013-01-01

    Recent findings suggest that sleep might serve a role in emotional coping. However, most findings are based on subjective reports of sleep quality, while the relation with underlying sleep physiology is still largely unknown. In this study, the impact of an emotionally distressing experience on the EEG correlates of sleep was assessed. In addition, the association between sleep physiological parameters and the extent of emotional attenuation over sleep was determined. The experimental set up involved presentation of an emotionally neutral or distressing film fragment in the evening, followed by polysomnographic registration of undisturbed, whole-night sleep and assessment of emotional reactivity to film cues on the next evening. We found that emotional distress induced mild sleep deterioration, but also an increase in the proportion of slow wave sleep (SWS) and altered patterning of rapid eye movement (REM) sleep. Indeed, while REM sleep occurrence normally increases over the course of the night, emotional distress flattened this distribution and correlated with an increased number of REM periods. While sleep deterioration was negatively associated to emotional attenuation over sleep, the SWS response was positively related to such attenuation and may form part of a compensatory response to the stressor. Interestingly, trait-like SWS characteristics also correlated positively with the extent of emotion attenuation over sleep. The combined results provide strong evidence for an intimate reciprocal relation between sleep physiology and emotional processing. Moreover, individual differences in subjects' emotional and sleep responses suggest there may be a coupling of certain emotion and sleep traits into distinct emotional sleep types. PMID:23671601

  6. Sleep, Torpor and Memory Impairment

    NASA Astrophysics Data System (ADS)

    Palchykova, S.; Tobler, I.

    It is now well known that daily torpor induces a sleep deficit. Djungarian hamsters emerging from this hypometabolic state spend most of the time in sleep. This sleep is characterized by high initial values of EEG slow-wave activity (SWA) that monotonically decline during recovery sleep. These features resemble the changes seen in numerous species during recovery after prolonged wakefulness or sleep deprivation (SD). When hamsters are totally or partially sleep deprived immediately after emerging from torpor, an additional increase in SWA can be induced. It has been therefore postulated, that these slow- waves are homeostatically regulated, as predicted by the two-process model of sleep regulation, and that during daily torpor a sleep deficit is accumulated as it is during prolonged waking. The predominance of SWA in the frontal EEG observed both after SD and daily torpor provides further evidence for the similarity of these conditions. It has been shown in several animal and human studies that sleep can enhance memory consolidation, and that SD leads to memory impairment. Preliminary data obtained in the Djungarian hamster showed that both SD and daily torpor result in object recognition deficits. Thus, animals subjected to SD immediately after learning, or if they underwent an episode of daily torpor between learning and retention, displayed impaired recognition memory for complex object scenes. The investigation of daily torpor can reveal mechanisms that could have important implications for hypometabolic state induction in other mammalian species, including humans.

  7. High-Intensity Continuous Wave Slow Positron Source at Jefferson Lab

    NASA Astrophysics Data System (ADS)

    Golge, Serkan; Vlahovic, Branislav; Wojtsekhowski, Bogdan

    2013-04-01

    We present a novel concept of an electron linac-based slow positron source with projected intensity on the order of 10^10 slow e^+/s. The key components of this concept are a Continuous Wave (CW) electron beam, a rotating positron-production target, a synchronized raster/anti-raster, a transport channel, and extraction of positrons into a field-free area through a magnetic field terminator plug for moderation in a solid Neon moderator. The feasibility calculations were completed in the framework of GEANT4 simulation and OPERA-3D magnetic field calculation code.

  8. Frequency-dependent damping in propagating slow magneto-acoustic waves

    SciTech Connect

    Prasad, S. Krishna; Banerjee, D.; Van Doorsselaere, T.

    2014-07-10

    Propagating slow magneto-acoustic waves are often observed in polar plumes and active region fan loops. The observed periodicities of these waves range from a few minutes to a few tens of minutes and their amplitudes were found to decay rapidly as they travel along the supporting structure. Previously, thermal conduction, compressive viscosity, radiation, density stratification, and area divergence were identified to be some of the causes for change in the slow wave amplitude. Our recent studies indicate that the observed damping in these waves is frequency-dependent. We used imaging data from the Solar Dynamics Observatory/Atmospheric Imaging Assembly to study this dependence in detail and for the first time via observations we attempted to deduce a quantitative relation between the damping length and frequency of these oscillations. We developed a new analysis method to obtain this relation. The observed frequency dependence does not seem to agree with the current linear wave theory and it was found that the waves observed in the polar regions show a different dependence from those observed in the on-disk loop structures despite the similarity in their properties.

  9. Estimation of material parameters from slow and fast shear waves in an incompressible, transversely isotropic material.

    PubMed

    Tweten, Dennis J; Okamoto, Ruth J; Schmidt, John L; Garbow, Joel R; Bayly, Philip V

    2015-11-26

    This paper describes a method to estimate mechanical properties of soft, anisotropic materials from measurements of shear waves with specific polarization and propagation directions. This method is applicable to data from magnetic resonance elastography (MRE), which is a method for measuring shear waves in live subjects or in vitro samples. Here, we simulate MRE data using finite element analysis. A nearly incompressible, transversely isotropic (ITI) material model with three parameters (shear modulus, shear anisotropy, and tensile anisotropy) is used, which is appropriate for many fibrous, biological tissues. Both slow and fast shear waves travel concurrently through such a material with speeds that depend on the propagation direction relative to fiber orientation. A three-parameter estimation approach based on directional filtering and isolation of slow and fast shear wave components (directional filter inversion, or DFI) is introduced. Wave speeds of each isolated shear wave component are estimated using local frequency estimation (LFE), and material properties are calculated using weighted least squares. Data from multiple finite element simulations are used to assess the accuracy and reliability of DFI for estimation of anisotropic material parameters. PMID:26476762

  10. A System and Method for Online High-Resolution Mapping of Gastric Slow-Wave Activity

    PubMed Central

    Bull, Simon H.; O’Grady, Gregory; Du, Peng

    2015-01-01

    High-resolution (HR) mapping employs multielectrode arrays to achieve spatially detailed analyses of propagating bioelectrical events. A major current limitation is that spatial analyses must currently be performed “off-line” (after experiments), compromising timely recording feedback and restricting experimental interventions. These problems motivated development of a system and method for “online” HR mapping. HR gastric recordings were acquired and streamed to a novel software client. Algorithms were devised to filter data, identify slow-wave events, eliminate corrupt channels, and cluster activation events. A graphical user interface animated data and plotted electrograms and maps. Results were compared against off-line methods. The online system analyzed 256-channel serosal recordings with no unexpected system terminations with a mean delay 18 s. Activation time marking sensitivity was 0.92; positive predictive value was 0.93. Abnormal slow-wave patterns including conduction blocks, ectopic pacemaking, and colliding wave fronts were reliably identified. Compared to traditional analysis methods, online mapping had comparable results with equivalent coverage of 90% of electrodes, average RMS errors of less than 1 s, and CC of activation maps of 0.99. Accurate slow-wave mapping was achieved in near real-time, enabling monitoring of recording quality and experimental interventions targeted to dysrhythmic onset. This work also advances the translation of HR mapping toward real-time clinical application. PMID:24860024

  11. Modeling of Reflective Propagating Slow-mode Wave in a Flaring Loop

    NASA Astrophysics Data System (ADS)

    Fang, X.; Yuan, D.; Van Doorsselaere, T.; Keppens, R.; Xia, C.

    2015-11-01

    Quasi-periodic propagating intensity disturbances have been observed in large coronal loops in extreme ultraviolet images over a decade, and are widely accepted to be slow magnetosonic waves. However, spectroscopic observations from Hinode/EIS revealed their association with persistent coronal upflows, making this interpretation debatable. We perform a 2.5D magnetohydrodynamic simulation to imitate the chromospheric evaporation and the following reflected patterns in a flare loop. Our model encompasses the corona, transition region, and chromosphere. We demonstrate that the quasi periodic propagating intensity variations captured by the synthesized Solar Dynamics Observatory/Atmospheric Imaging Assembly 131, 94 Å emission images match the previous observations well. With particle tracers in the simulation, we confirm that these quasi periodic propagating intensity variations consist of reflected slow mode waves and mass flows with an average speed of 310 km s‑1 in an 80 Mm length loop with an average temperature of 9 MK. With the synthesized Doppler shift velocity and intensity maps of the Solar and Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation Fe xix line emission, we confirm that these reflected slow mode waves are propagating waves.

  12. Simulating Reflective Propagating Slow-wave/flow in a Flaring Loop

    NASA Astrophysics Data System (ADS)

    Fang, X.

    2015-12-01

    Quasi-periodic propagating intensity disturbances have been observed in large coronal loops in EUV images over a decade, and are widely accepted to be slow magnetosonic waves. However, spectroscopic observations from Hinode/EIS revealed their association with persistent coronal upflows, making this interpretation debatable. We perform a 2.5D magnetohydrodynamic simulation to imitate the chromospheric evaporation and the following reflected patterns in a post flare loop. Our model encompasses the corona, transition region, and chromosphere. We demonstrate that the quasi periodic propagating intensity variations captured by our synthesized AIA 131, 94~Å~emission images match the previous observations well. With particle tracers in the simulation, we confirm that these quasi periodic propagating intensity variations consist of reflected slow mode waves and mass flows with an average speed of 310 km/s in an 80 Mm length loop with an average temperature of 9 MK. With the synthesized Doppler shift velocity and intensity maps in SUMER Fe XIX line emission, we confirm that these reflected slow mode waves are propagating waves.

  13. Cortical Processing of Respiratory Afferent Stimuli during Sleep in Children with the Obstructive Sleep Apnea Syndrome

    PubMed Central

    Huang, Jingtao; Colrain, Ian M.; Melendres, M. Cecilia; Karamessinis, Laurie R.; Pepe, Michelle E.; Samuel, John M.; Abi-Raad, Ronald F.; Trescher, William H.; Marcus, Carole L.

    2008-01-01

    Study Objectives: Children with the obstructive sleep apnea syndrome (OSAS) have blunted upper airway responses to negative pressure, but the underlying cause remains unknown. Cortical processing of respiratory afferent information can be tested by measuring respiratory-related evoked potentials (RREPs). We hypothesized that children with OSAS have blunted RREP responses compared to normal children during sleep. Design: During sleep, RREPs were obtained from EEG electrodes Fz, Cz, Pz during stage 2 sleep, slow wave sleep (SWS), and REM sleep. RREPs were produced with multiple short occlusions of the upper airway. Setting: Sleep laboratory. Participants: 9 children with OSAS and 12 normal controls. Measurements and Results: Children with OSAS had significantly decreased evoked K-complex production in stage 2 sleep and slow wave sleep and significantly reduced RREP N350 and P900 components in slow wave sleep. There were no significant differences in any of the measured RREP components in stage 2 sleep, and the only REM difference was decreased P2 amplitude. Conclusions: Results indicate that in children with OSAS, cortical processing of respiratory-related information measured with RREPs persists throughout sleep; however, RREPs during SWS are blunted compared to those seen in control children. Possible causes for this difference include a congenital deficit in neural processing reflective of a predisposition to develop OSAS, or changes in the upper airway rendering the airway less capable of transducing pressure changes following occlusion. Further research is required to evaluate RREPs after effective surgical treatment of OSAS in children, in order to distinguish between these alternatives. Citation: Huang J; Colrain IM; Melendres MC; Karamessinis LR; Pepe ME; Samuel JM; Abi-Raad RF; Trescher WH; Marcus CL. Cortical processing of respiratory afferent stimuli during sleep in children with the obstructive sleep apnea syndrome. SLEEP 2007;31(3):403-410. PMID:18363317

  14. Initiation of sleep-dependent cortical-hippocampal correlations at wakefulness-sleep transition.

    PubMed

    Haggerty, Daniel C; Ji, Daoyun

    2014-10-01

    Sleep is involved in memory consolidation. Current theories propose that sleep-dependent memory consolidation requires active communication between the hippocampus and neocortex. Indeed, it is known that neuronal activities in the hippocampus and various neocortical areas are correlated during slow-wave sleep. However, transitioning from wakefulness to slow-wave sleep is a gradual process. How the hippocampal-cortical correlation is established during the wakefulness-sleep transition is unknown. By examining local field potentials and multiunit activities in the rat hippocampus and visual cortex, we show that the wakefulness-sleep transition is characterized by sharp-wave ripple events in the hippocampus and high-voltage spike-wave events in the cortex, both of which are accompanied by highly synchronized multiunit activities in the corresponding area. Hippocampal ripple events occur earlier than the cortical high-voltage spike-wave events, and hippocampal ripple incidence is attenuated by the onset of cortical high-voltage spike waves. This attenuation leads to a temporary weak correlation in the hippocampal-cortical multiunit activities, which eventually evolves to a strong correlation as the brain enters slow-wave sleep. The results suggest that the hippocampal-cortical correlation is established through a concerted, two-step state change that first synchronizes the neuronal firing within each brain area and then couples the synchronized activities between the two regions. PMID:25008411

  15. Initiation of sleep-dependent cortical-hippocampal correlations at wakefulness-sleep transition

    PubMed Central

    Haggerty, Daniel C.

    2014-01-01

    Sleep is involved in memory consolidation. Current theories propose that sleep-dependent memory consolidation requires active communication between the hippocampus and neocortex. Indeed, it is known that neuronal activities in the hippocampus and various neocortical areas are correlated during slow-wave sleep. However, transitioning from wakefulness to slow-wave sleep is a gradual process. How the hippocampal-cortical correlation is established during the wakefulness-sleep transition is unknown. By examining local field potentials and multiunit activities in the rat hippocampus and visual cortex, we show that the wakefulness-sleep transition is characterized by sharp-wave ripple events in the hippocampus and high-voltage spike-wave events in the cortex, both of which are accompanied by highly synchronized multiunit activities in the corresponding area. Hippocampal ripple events occur earlier than the cortical high-voltage spike-wave events, and hippocampal ripple incidence is attenuated by the onset of cortical high-voltage spike waves. This attenuation leads to a temporary weak correlation in the hippocampal-cortical multiunit activities, which eventually evolves to a strong correlation as the brain enters slow-wave sleep. The results suggest that the hippocampal-cortical correlation is established through a concerted, two-step state change that first synchronizes the neuronal firing within each brain area and then couples the synchronized activities between the two regions. PMID:25008411

  16. Evaluation of Some Slow-wave Vane Structures for Aminiature Traveling-wave Tube at 30 Ghz

    NASA Technical Reports Server (NTRS)

    Kavanagh, Frank; Ebihara, Ben; Wallett, Thomas M.; Dayton, James A., Jr.

    1994-01-01

    The dispersion characteristics of six vane type slow wave structures were experimentally measured near 1 GHz to determine applicability in an electrostatically focused 30 GHz miniature traveling wave tube (TWT). From the measured results, the trapezoidal vane structure appeared to be the most promising exhibiting an interaction impedance equal to 337.9 ohms at beta(L)/pi equal to 0.3. A 30 GHz trapezoidal vane structure with coupling irises was fabricated using electrical discharge machining (EDM). This structure, however, was too lossy for a short electrostatically focused tube, but several of the structures are amenable to a tube with permanent magnetic focusing.

  17. Do birds sleep in flight?

    NASA Astrophysics Data System (ADS)

    Rattenborg, Niels C.

    2006-09-01

    The following review examines the evidence for sleep in flying birds. The daily need to sleep in most animals has led to the common belief that birds, such as the common swift ( Apus apus), which spend the night on the wing, sleep in flight. The electroencephalogram (EEG) recordings required to detect sleep in flight have not been performed, however, rendering the evidence for sleep in flight circumstantial. The neurophysiology of sleep and flight suggests that some types of sleep might be compatible with flight. As in mammals, birds exhibit two types of sleep, slow-wave sleep (SWS) and rapid eye-movement (REM) sleep. Whereas, SWS can occur in one or both brain hemispheres at a time, REM sleep only occurs bihemispherically. During unihemispheric SWS, the eye connected to the awake hemisphere remains open, a state that may allow birds to visually navigate during sleep in flight. Bihemispheric SWS may also be possible during flight when constant visual monitoring of the environment is unnecessary. Nevertheless, the reduction in muscle tone that usually accompanies REM sleep makes it unlikely that birds enter this state in flight. Upon landing, birds may need to recover the components of sleep that are incompatible with flight. Periods of undisturbed postflight recovery sleep may be essential for maintaining adaptive brain function during wakefulness. The recent miniaturization of EEG recording devices now makes it possible to measure brain activity in flight. Determining if and how birds sleep in flight will contribute to our understanding of a largely unexplored aspect of avian behavior and may also provide insight into the function of sleep.

  18. Evidence of Biot Slow Waves in Electroseismic Measurementss on Laboratory-Scale

    NASA Astrophysics Data System (ADS)

    Devi, M. S.

    2015-12-01

    Electroseismic methods which are the opposite of seismo-electric methods have only been little investigated up to now especially in the near surface scale. These methods can generate the solid-fluid relative movement induced by the electric potential in fluid-filled porous media. These methods are the response of electro-osmosis due to the presence of the electrical double layer. Laboratory experiments and numerical simulations of electroseismic studies have been performed. Electroseismic measurements conducted in micro glass beads saturated with demineralized water. Pair of 37 x 37 mm square aluminium grids with 2 mm of aperture and 4 mm of spacing is used as the electric dipole that connected to the electric power source with the voltage output 150 V. A laser doppler vibrometer is the system used to measure velocity of vibrating objects during measurements by placing a line of reflective paper on the surface of media that scattered back a helium-neon laser. The results in homogeneous media shows that the compressional waves induced by an electric signal. We confirm that the results are not the effects of thermal expansion. We also noticed that there are two kinds of the compressional waves are recorded: fast and slow P-waves. The latter, Biot slow waves, indicate the dominant amplitude. Moreover, we found that the transition frequency (ωc) of Biot slow waves depends on mechanical parameters such as porosity and permeability. The ωc is not affected when varying conductivity of the fluid from 25 - 320 μS/cm, although the amplitude slightly changed. For the results in two layer media by placing a sandstone as a top layer shows that a large amount of transmission seismic waves (apparently as Biot slow waves) rather than converted electromagnetic-to-seismic waves. These properties have also been simulated with full waveform numerical simulations relying on Pride's (1994) using our computer code (Garambois & Dietrich, 2002). If it is true that the electric source in

  19. Shifting from Implicit to Explicit Knowledge: Different Roles of Early- and Late-Night Sleep

    ERIC Educational Resources Information Center

    Yordanova, Juliana; Kolev, Vasil; Verleger, Rolf; Bataghva, Zhamak; Born, Jan; Wagner, Ullrich

    2008-01-01

    Sleep has been shown to promote the generation of explicit knowledge as indicated by the gain of insight into previously unrecognized task regularities. Here, we explored whether this generation of explicit knowledge depends on pre-sleep implicit knowledge, and specified the differential roles of slow-wave sleep (SWS) vs. rapid eye movement (REM)…

  20. [Night sleep patterns in post-operative intensive care patients (author's transl)].

    PubMed

    Landau-Ferey, J; Rebelo, F; Glaser, P; Garma, L

    1977-01-01

    5 patients admitted to intensive care following post-operative complications had EEG recordings on 2 consecutive nights some time after their operations. Study of the different sleep stages showed a marked increase in deep slow wave sleep and waking but asignificant reduction in light slow wave sleep and paradoxical sleep. The appearance of the sleep cycles through the night was unusual with respect to the maximum occurrence of the various stages and their evolution. Finally certain characteristics of paradoxical sleep, the rhythm and duration of the phases and the number and frequency of ocular movements were also modified. Comparison of these findings with those previously reported show that these abnormalities, rather than suggesting sleep deprivation resemble more closely the fidings in shift workers when they resume night sleep after a period of day sleep. The also resemble the changes seen in people whose circadian rhythm has been displaced by 12 hours. PMID:565525

  1. Gender differences in sleep in older men and women.

    PubMed

    Guidozzi, F

    2015-10-01

    Sleep disturbances increase with increasing age in both males and females and become fairly common in the older community when compared to their younger counterparts. Even though these sleep disturbances increase with advancing age, there are nevertheless inherent differences in sleep disturbances between males and females. When compared to older men, older women will have a longer sleep latency (number of minutes it takes to fall asleep), more daytime sleepiness, will sleep about 20 min less per day, have less NREM stages 1 and 2 sleep, have more slow-wave sleep, and are more predisposed to REM sleep. Women have at least a 40% increased risk for developing insomnia, are at twice the risk for restless legs syndrome, will have different obstructive sleep apnea symptoms and more partial obstructions during sleep compared to men. They are also less likely to use antidepressants but will metabolize zolpidem 50% slower than men. PMID:26249643

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

    PubMed

    Nobili, Lino; Ferrara, Michele; Moroni, Fabio; De Gennaro, Luigi; Russo, Giorgio Lo; Campus, Claudio; Cardinale, Francesco; De Carli, Fabrizio

    2011-09-15

    Sleep is traditionally considered a global process involving the whole brain. However, recent studies have shown that sleep depth is not evenly distributed within the brain. Sleep disorders, such as sleepwalking, also suggest that EEG features of sleep and wakefulness might be simultaneously present in different cerebral regions. In order to probe the coexistence of dissociated (wake-like and sleep-like) electrophysiological behaviors within the sleeping brain, we analyzed intracerebral electroencephalographic activity drawn from sleep recordings of five patients with pharmacoresistant focal epilepsy without sleep disturbances, who underwent pre-surgical intracerebral electroencephalographic investigation. We applied spectral and wavelet transform analysis techniques to electroencephalographic data recorded from scalp and intracerebral electrodes localized within the Motor cortex (Mc) and the dorso-lateral Prefrontal cortex (dlPFc). The Mc showed frequent Local Activations (lasting from 5 to more than 60s) characterized by an abrupt interruption of the sleep electroencephalographic slow waves pattern and by the appearance of a wake-like electroencephalographic high frequency pattern (alpha and/or beta rhythm). Local activations in the Mc were paralleled by a deepening of sleep in other regions, as expressed by the concomitant increase of slow waves in the dlPFc and scalp electroencephalographic recordings. These results suggest that human sleep can be characterized by the coexistence of wake-like and sleep-like electroencephalographic patterns in different cortical areas, supporting the hypothesis that unusual phenomena, such as NREM parasomnias, could result from an imbalance of these two states. PMID:21718789

  3. Is sleep-related verbal memory consolidation impaired in sleepwalkers?

    PubMed

    Uguccioni, Ginevra; Pallanca, Olivier; Golmard, Jean-Louis; Leu-Semenescu, Smaranda; Arnulf, Isabelle

    2015-04-01

    In order to evaluate verbal memory consolidation during sleep in subjects experiencing sleepwalking or sleep terror, 19 patients experiencing sleepwalking/sleep terror and 19 controls performed two verbal memory tasks (16-word list from the Free and Cued Selective Reminding Test, and a 220- and 263-word modified story recall test) in the evening, followed by nocturnal video polysomnography (n = 29) and morning recall (night-time consolidation after 14 h, n = 38). The following morning, they were given a daytime learning task using the modified story recall test in reverse order, followed by an evening recall test after 9 h of wakefulness (daytime consolidation, n = 38). The patients experiencing sleepwalking/sleep terror exhibited more frequent awakenings during slow-wave sleep and longer wakefulness after sleep onset than the controls. Despite this reduction in sleep quality among sleepwalking/sleep terror patients, they improved their scores on the verbal tests the morning after sleep compared with the previous evening (+16 ± 33%) equally well as the controls (+2 ± 13%). The performance of both groups worsened during the daytime in the absence of sleep (-16 ± 15% for the sleepwalking/sleep terror group and -14 ± 11% for the control group). There was no significant correlation between the rate of memory consolidation and any of the sleep measures. Seven patients experiencing sleepwalking also sleep-talked during slow-wave sleep, but their sentences were unrelated to the tests or the list of words learned during the evening. In conclusion, the alteration of slow-wave sleep during sleepwalking/sleep terror does not noticeably impact on sleep-related verbal memory consolidation. PMID:25212397

  4. A Framework for the Online Analysis of Multi-Electrode Gastric Slow Wave Recordings

    PubMed Central

    Bull, Simon H.; O’Grady, Greg; Cheng, Leo K.; Pullan, Andrew J.

    2014-01-01

    High resolution mapping of electrical activity is becoming an important technique for analysing normal and dysrhythmic gastrointestinal (GI) slow wave activity. Several methods are used to extract meaningful information from the large quantities of data obtained, however, at present these methods can only be used offline. Thus, all analysis currently performed is retrospective and done after the recordings have finished. Limited information about the quality or characteristics of the data is therefore known while the experiments take place. Building on these offline analysis methods, an online implementation has been developed that identifies and displays slow wave activations working alongside an existing recording system. This online system was developed by adapting existing and novel signal processing techniques and linking these to a new user interface to present the extracted information. The system was tested using high resolution porcine data, and will be applied in future high resolution mapping studies allowing researchers to respond in real time to experimental observations. PMID:22254663

  5. Efficiency enhancement of high power vacuum BWO's using nonuniform slow wave structures

    SciTech Connect

    Moreland, L.D.; Schamiloglu, E. . Pulsed Power and Plasma Science Lab.); Lemke, R.W. ); Korovin, S.D.; Rostov, V.V.; Roitman, A.M. . Inst. of High Current Electronics); Hendricks, K.J.; Spencer, T.A. . Advanced Weapons and Survivability Directorate)

    1994-10-01

    The Sinus-6, a high-power relativistic repetitively-pulsed electron beam accelerator, is used to drive various slow wave structures in a BWO configuration in vacuum. Peak output power of about 550 MW at 9.45 GHz was radiated in an 8-ns pulse. The authors describe experiments which study the relative efficiencies of microwave generation from a two-stage nonuniform amplitude slow wave structure and its variations without an initial stage. Experimental results are compared with 2.5 D particle-in-cell computer simulations. The results suggest that prebunching the electron beam in the initial section of the nonuniform BWO results in increased microwave generation efficiency. Furthermore, simulations reveal that, in addition to the backward propagating surface harmonic of the TM[sub 01] mode, backward and forward propagating volume harmonics with phase velocity twice that of the surface harmonic play an important role in high-power microwave generation and radiation.

  6. THE SLOW-MODE NATURE OF COMPRESSIBLE WAVE POWER IN SOLAR WIND TURBULENCE

    SciTech Connect

    Howes, G. G.; Klein, K. G.; TenBarge, J. M.; Bale, S. D.; Chen, C. H. K.; Salem, C. S.

    2012-07-01

    We use a large, statistical set of measurements from the Wind spacecraft at 1 AU, and supporting synthetic spacecraft data based on kinetic plasma theory, to show that the compressible component of inertial range solar wind turbulence is primarily in the kinetic slow mode. The zero-lag cross-correlation C({delta}n, {delta}B{sub ||}) between proton density fluctuations {delta}n and the field-aligned (compressible) component of the magnetic field {delta}B{sub ||} is negative and close to -1. The typical dependence of C({delta}n, {delta}B{sub ||}) on the ion plasma beta {beta}{sub i} is consistent with a spectrum of compressible wave energy that is almost entirely in the kinetic slow mode. This has important implications for both the nature of the density fluctuation spectrum and for the cascade of kinetic turbulence to short wavelengths, favoring evolution to the kinetic Alfven wave mode rather than the (fast) whistler mode.

  7. Role of cardiorespiratory synchronization and sleep physiology: effects on membrane potential in the restorative functions of sleep.

    PubMed

    Jerath, Ravinder; Harden, Kyler; Crawford, Molly; Barnes, Vernon A; Jensen, Mike

    2014-03-01

    Although sleep physiology has been extensively studied, many of the cellular processes that occur during sleep and the functional significance of sleep remain unclear. The degree of cardiorespiratory synchronization during sleep increases during the progression of slow-wave sleep (SWS). Autonomic nervous system (ANS) activity also assumes a pattern that correlates with the progression of sleep. The ANS is an integral part of physiologic processes that occur during sleep with the respective contribution of parasympathetic and sympathetic activity varying between different sleep stages. In our paper, we attempt to unify the activities of various physiologic systems, namely the cardiac, respiratory, ANS and brain, during sleep into a consolidated picture with particular attention to the membrane potential of neurons. In our unified model, we explore the potential of sleep to promote restorative processes in the brain. PMID:24548599

  8. Over-reflection of slow magnetosonic waves by homogeneous shear flow: Analytical solution

    SciTech Connect

    Dimitrov, Z. D.; Maneva, Y. G.; Hristov, T. S.; Mishonov, T. M.

    2011-08-15

    We have analyzed the amplification of slow magnetosonic (or pseudo-Alfvenic) waves (SMW) in incompressible shear flow. As found here, the amplification depends on the component of the wave-vector perpendicular to the direction of the shear flow. Earlier numerical results are consistent with the general analytic solution for the linearized magnetohydrodynamic equations, derived here for the model case of pure homogeneous shear (without Coriolis force). An asymptotically exact analytical formula for the amplification coefficient is derived for the case when the amplification is sufficiently large.

  9. Slow Feature Analysis on Retinal Waves Leads to V1 Complex Cells

    PubMed Central

    Dähne, Sven; Wilbert, Niko; Wiskott, Laurenz

    2014-01-01

    The developing visual system of many mammalian species is partially structured and organized even before the onset of vision. Spontaneous neural activity, which spreads in waves across the retina, has been suggested to play a major role in these prenatal structuring processes. Recently, it has been shown that when employing an efficient coding strategy, such as sparse coding, these retinal activity patterns lead to basis functions that resemble optimal stimuli of simple cells in primary visual cortex (V1). Here we present the results of applying a coding strategy that optimizes for temporal slowness, namely Slow Feature Analysis (SFA), to a biologically plausible model of retinal waves. Previously, SFA has been successfully applied to model parts of the visual system, most notably in reproducing a rich set of complex-cell features by training SFA with quasi-natural image sequences. In the present work, we obtain SFA units that share a number of properties with cortical complex-cells by training on simulated retinal waves. The emergence of two distinct properties of the SFA units (phase invariance and orientation tuning) is thoroughly investigated via control experiments and mathematical analysis of the input-output functions found by SFA. The results support the idea that retinal waves share relevant temporal and spatial properties with natural visual input. Hence, retinal waves seem suitable training stimuli to learn invariances and thereby shape the developing early visual system such that it is best prepared for coding input from the natural world. PMID:24810948

  10. Numerical calculation of electromagnetic eigenfields and dispersion relation for slow-wave device simulation

    SciTech Connect

    Oslake, J.M.; Verboncoeur, J.P.; Birdsall, C.K.

    1996-12-31

    Slow-wave structures support microwave amplification via electromagnetic coupling with an injected electron beam. Critical in the design of such devices is the dependence of the dispersion relation on the geometry of the guiding structure. The dispersion relation provides phase and group velocities, and the fields provide the impedance as seen by the beam. To this end, a computer model is developed which first numerically solves a wave equation in finite difference from subject to boundary conditions periodic in z and conducting elsewhere. Here the direction of wave propagation is along the z-axis. The solution produces a sequence of eigenfrequencies and eigenfields beginning with cut-off. Fourier decomposition of each eigenfield along selected mesh lines coincident with the location of the electron beam is then performed to establish a correspondence between eigenfrequency and wave number. From this data the dispersion relation for the slow-wave structure can then be formed. An example showing the first two TM passbands and E{sub z} fields for a slotted waveguide in xz coordinates is demonstrated. The authors plan to incorporate plasma loading with space-time dependent dielectric constant.