• 대한의용생체공학회:의공학회지
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• 제37권4호
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• pp.127-133
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• 2016

This study proposes the feasibility for automatic classification of sleep/wakefulness using nasal pressure in patients with sleep-disordered breathing (SDB). First, SDB events were detected using the methods developed in our previous studies. In epochs for normal breathing, we extracted the features for classifying sleep/wakefulness based on time-domain, frequency-domain and non-linear analysis. And then, we conducted the independent two-sample t-test and calculated Mahalanobis distance (MD) between the two categories. As a results, $SD_{LEN}$ (MD = 0.84, p < 0.01), $P_{HF}$ (MD = 0.81, p < 0.01), $SD_{AMP}$ (MD = 0.76, p = 0.031) and $MEAN_{AMP}$ (MD = 0.75, p = 0.027) were selected as optimal feature. We classified sleep/wakefulness based on support vector machine (SVM). The classification results showed mean of sensitivity (Sen.), specificity (Spc.) and accuracy (Acc.) of 60.5%, 89.0% and 84.8% respectively. This method showed the possibilities to automatically classify sleep/wakefulness only using nasal pressure.

• Safety and Health at Work
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• 제7권2호
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• pp.120-123
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• 2016

Background: To assess in a laboratory setting the ability to stay awake in a sample of workers of an Italian hospital and to investigate the association between that ability and the risk of occupational injury. Methods: Nine workers at the University Hospital of Udine who reported an occupational injury in the study period (cases), and seven noninjured workers (controls) underwent a polysomnography and four 40-minute maintenance of wakefulness tests (MWT). Differences in sleep characteristics and in wakefulness maintenance were assessed using Wilcoxon's rank sums tests and Fisher's exact tests. Results: Controls had greater sleep latency, lower total sleep time, fewer leg movements, and a higher percentage ratio of cycling alternating pattern, were more likely not to fall asleep during the MWT and were less likely to have two or more sleep onsets. Although not all the differences reached statistical significance, cases had lower sleep onset times in Trials 1-3. Conclusion: In the literature, the evidence of an association between MWT results and real life risk of accidents is weak. Our results suggest a relationship between the MWT results and the risk of injury among hospital workers.

• Journal of Ginseng Research
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• 제34권1호
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• pp.30-40
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• 2010

The present investigation was conducted to evaluate the regulation of sleep architecture by the red ginseng water extract (RGE) in acutely and chronically restraint stressed rats. Adult rats were fitted with sleep.wake recording electrodes. Following post-surgical recovery, rats were extensively habituated for freely moving polygraphic recording conditions. Polygraphic signs of sleep-wake activities were recorded for 24 h after RGE administration and induction of stress and were analyzed to understand the regulation of sleep architecture. Acute stress decreased wakefulness and increased total sleep, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep in both the daytime and nighttime recording. RGE shortened the daytime NREM and REM sleep, without changing the wakefulness and total sleep. RGE increased nighttime wakefulness, and decreased total, NREM and REM sleep. Chronic stress increased wakefulness and decreased total sleep in the daytime recording, and increased REM and decreased NREM sleep in both the day and night time recording. RGE ameliorated chronic stress and induced alterations of REM and NREM sleep in the day and night time sleep architecture. Acute and chronic stress could also induce alternations in cortex electroencephalogram (EEG) recording during NREM, REM sleep and wakefulness. These findings suggest that RGE may modulate the sleep behavior in acutely and chronically stressed rats and the ameliorating effect of RGE on the sleep architecture may involve in modulation of $\alpha$-, $\theta$- and $\delta$- wave activities of the cortical EEG.

• 수면정신생리
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• 제16권1호
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• pp.22-27
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• 2009

Regulation of respiration differs significantly between wakefulness and sleep. Respiration during wakefulness is influenced by not only automatic control but also voluntary and behavioral control. Sleep is associated with definite changes in respiratory function. With the onset of sleep, voluntary control of ventilation that overrides automatic control during wakefulness becomes terminated. Also ventilatory response to various stimuli including hypoxemia and hypercapnia is decreased. With these reasons respiration during sleep becomes fragile and unstable so that marked hypoxemia can be happened in patients with lung disease especially during REM sleep. Obstructive sleep apnea may also be developed if upper airway resistance is increased in addition to these blunted ventilatory responses.

• Natural Product Sciences
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• 제15권4호
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• pp.213-221
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• 2009

Longanae Arillus (the rind of fruits of Dimocarpus longan) has been consumed for the treatment of insomnia and anxiety in Asia. To provide further scientific basis to traditional uses of this fruit on insomnia, we evaluated the effects of methanol extract of Longanae Arillus (MELA) on the alteration of sleep architecture and electroencephalogram (EEG) power spectra in acutely and chronically restraint-stressed rats. Following postsurgical recovery, Polygraphic signs of sleep-wake activities were recorded for 24 h after MELA administration in rats. Rats in the acute stress and chronic stress were administered with MELA for 10 days. On the $8^{th},\;9^{th}\;and\;10^{th}$ day of MELA administration, the rats were stressed for 3 h once per day. On the $10^{th}$ day and 1 h after MELA administration, the rats were stressed once for 22 h in the chronic stress group. Acute and chronic stress induced alternations in cortex EEG recordings during non-rapid eye movement (NREM), rapid eye movement (REM) sleep and wakefulness. MELA shortened the total and REM sleep and increased the wakefulness in night time recording without changing daytime recordings. Chronic stress increased wakefulness and REM sleep, decreased total and NREM sleep in the daytime recording, and increased REM and decreased NREM sleep without changing total sleep and wakefulness in night time recording. These findings suggest that MELA ameliorated the alterations in REM and NREM sleep of acutely and chronically stressed rats via modulation of cortical ${\alpha}-$, ${\theta}-$ and ${\delta}-$ wave activity.

• 생물정신의학
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• 제19권1호
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• pp.65-69
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• 2012

Objectives : Much is still unknown about the neurophysiological mechanisms or dynamics of the sleep onset process. Detrended fluctuation analysis (DFA) is a new tool for the analysis of electroencephalography (EEG) that may give us additional information about electrophysiological changes. The purpose of this study is to analyze long-range correlations of electroencephalographic signals by DFA and their changes in the sleep onset process. Methods : Thirty channel EEG was recorded in 61 healthy subjects (male:female=34:27, age=$27.2{\pm}3.0$ years). The scaling exponents, alpha, were calculated by DFA and compared between four kinds of 30s sleep-wakefulness states such as wakefulness, transition period, early sleep, and late sleep (stage 1). These four states were selected by the distribution of alpha and theta waves in O1 and O2 electrodes. Results : The scaling exponents, alpha, were significantly different in the four states during sleep onset periods, and also varied with the thirty leads. The interaction between the sleep states and the leads was significant. The means (${\pm}$ standard deviation) of alphas for the states were 0.94 (${\pm}0.12$), 0.98 (${\pm}0.12$), 1.10 (${\pm}0.10$), 1.07 (${\pm}0.07$) in the wakefulness, transitional period, early sleep and late sleep state respectively. The mean alpha of anterior fifteen leads was greater than that of posterior fifteen leads, and the two regions showed the different pattern of changes of the alpha during the sleep onset periods. Conclusions : The characteristic findings in the sleep onset period were the increasing pattern of scaling exponent of DFA, and the pattern was slightly but significantly different between fronto-temporal and parieto-occipital regions. It suggests that the long-range correlations of EEG have a tendency of increasing from wakefulness to early sleep, but anterior and posterior brain regions have different dynamical process. DFA, one of the nonlinear analytical methods for time series, may be a useful tool for the investigation of the sleep onset period.

• Journal of Sleep Medicine
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• 제15권2호
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• pp.62-67
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• 2018

Objectives: Restless leg syndrome (RLS) is a common sensorimotor disorder and is frequently associated with periodic limb movement in sleep (PLMS). Also about one third of patient with RLS have periodic limb movement during wakefulness (PLMW). However there is little research on the correlation between PLMW and RLS. We aimed to evaluate difference in sleep characteristics between patients with RLS with PLMW and those without PLMW. Methods: Our study included twenty eight RLS patients. Subjects underwent suggested immobilization test (SIT) prior to one full-night polysomnography study. Patients were classified into two groups according to the presence of PLMW based on SIT-PLMW index. Polysomnographic findings, subjective sleep quality, and hematologic results were analyzed and compared between the two groups. Results: Mean age of patient with frequent PLMW (SIT-PLMW ${\geq}40/hr$) was significantly higher. RLS patients with frequent PLMW were also significantly related to insomnia severity. The PLMS index was higher in patients with PLMW and showed a significant correlation with the PLMW index. Conclusions: PLMW influence sleep quality such as insomnia and is correlated with movement during sleep.

• 수면정신생리
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• 제16권1호
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• pp.16-21
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• 2009

In accordance with the development of EEG and polysomnography in the field of sleep research, the sleep onset period (SOP) between wakefulness and sleep has been considered an important part for understanding the physiology of sleep. SOP in the transition from wakefulness to sleep is a gradual process integrating various viewpoints such as behavior, EEG, physiology and subjective report. Particularly, based on understanding of EEG changes during sleep, SOP has been regarded as a pattern of topographical change in specific frequency and specific state in EEG. Studies on quantitative EEG (qEEG) and event-related potential (ERP) have suggested that SOP shows the changes of functional coordination at the specific cortical areas in qEEG and the changes of regular patterns in response to environmental stimulation in ERP. The development of sleep EEG and topographic mapping of EEG is expected to integrate various viewpoints of SOP and clarify the neurophysiologic mechanism of SOP further.

• BMB Reports
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• 제37권5호
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• pp.565-573
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• 2004

Orexin-A and orexin-B (hypocretin-1 and hypocretin-2, respectively) are important hypothalamic neuro-peptides, which are encoded by a single mRNA transcript and stimulate food intake as well as regulate wakefulness. Here we determined the solution structure of orexin-A by NMR spectroscopy and by simulated-annealing calculation. The structural features of orexin-A involve two $\alpha$-helices, with the hydrophobic residues disposed to on one side of helix, and hydrophilic residues to the other. A hydrophilic turn induced by two disulfide bonds provides the key difference between orexin-A and -B. With previous mutagenic studies, the derived structure of orexin-A provides us with a structure-functional view for novel drug design.

• 수면정신생리
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• 제6권1호
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• pp.19-25
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• 1999

Sleep alters both breathing pattern and the ventilatory responses to external stimuli. These changes during sleep permit the development or aggravation of sleep-related hypoxemia in patients with respiratory disease and contribute to the pathogenesis of apneas in patients with the sleep apnea syndrome. Fundamental effects of sleep on the ventilatory control system are 1) removal of wakefulness input to the upper airway leading to the increase in upper airway resistance, 2) loss of wakefulness drive to the respiratory pump, 3) compromise of protective respiratory reflexes, and 4) additional sleep-induced compromise of ventilatory control initiated by reduced functional residual capacity on supine position assumed in sleep, decreased $CO_2$ production during sleep, and increased cerebral blood flow in especially rapid eye movement(REM) sleep. These effects resulted in periodic breathing during unsteady non-rapid eye movement(NREM) sleep even in normal subjects, regular but low ventilation during steady NREM sleep, and irregular breathing during REM sleep. Sleep-induced breathing instabilities are divided due primarily to transient increase in upper airway resistance and those that involve overshoots and undershoots in neural feedback mechanisms regulating the timing and/or amplitude of respiratory output. Following ventilatory overshoots, breathing stability will be maintained if excitatory short-term potentiation is the prevailing influence. On the other hand, apnea and hypopnea will occur if inhibitory mechanisms dominate following the ventilatory overshoot. These inhibitory mechanisms include 1) hypocapnia, 2) inhibitory effect from lung stretch, 3) baroreceptor stimulation, 4) upper airway mechanoreceptor reflexes, 5) central depression by hypoxia, and 6) central system inertia. While the respiratory control system functions well during wakefulness, the control of breathing is commonly disrupted during sleep. These changes in respiratory control resulting in breathing instability during sleep are related with the pathophysiologic mechanisms of obstructive and/or central apnea, and have the therapeutic implications for nocturnal hypoventilation in patients with chronic obstructive pulmonary disease or alveolar hypoventilation syndrome.