Blood changes during physiological sleep

Summary The action of moderate stimulation of excitatory process in the central nervous system upon development of experimental tuberculosis was studied.Mice infected with tuberculosis received caffeine during 7 days before and 41 days after infection (0.05 mg subcutaneously).Macro- and microscopic research has shown that the number and size of tubercles, weight of lungs and spleen and weight coefficients of these organs are larger in mice not injected with caffeine. These mice also revealed some necrotic lesions in lungs which were not observed in mice injected.Thus repeated injections of caffeine increases resistance of animals against experimental tuberculosis and leads to atternuation of the specific process.Submitted by Active Member of the Academy of Medical Sciences of the USSR, V. N. Chernigovsky     

Blood changes during electrically induced sleep

Summary The change in the blood picture during electrically-induced sleep is associated with the function of the sleep as such. In deep sleep the number of leukocytes falls progressively at the expense of all the white blood cells. There is a rise in the number of erythrocytes and the hematocrit index. In a state of drowsiness the number of leukocytes does not drop and in individual instances it even rises; the erythrocyte count and hematocrit index are not increased so much as in deep sleep. On awaking, the leukocytic shift assumes a character which is just the opposite of that noted during profound sleep. In general, the fluctuations in hematological indices are within physiologically normal limits and analogous to those observed in natural sleep.(Presented by Active Member AMN SSSR V. N. Chernigovskii) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny Vol. 49, No. 5, pp. 51–54, May, 1960     

Cardiac changes during sleep in sleep-deprived infants

OBJECTIVE: To evaluate the influence of a brief period of sleep deprivation on cardiac autonomic controls during sleep in healthy infants. DESIGN: Twelve healthy infants with a median age of 8 weeks (range, 7 to 18 weeks) were recorded polygraphically during a morning and an afternoon nap in a sleep laboratory. They were sleep deprived for approximately 2 hours, either in the morning or in the afternoon, before being allowed to fall asleep. Six infants were sleep deprived before the morning nap, and 6 before the afternoon nap. During both naps, their sleep, breathing, and heart-rate characteristics were continuously recorded. Spectral analysis of heart rate was evaluated as a function of sleep stages. Two major peaks were recognizable: a low-frequency component related to sympathetic and parasympathetic activities and a high-frequency component reflecting parasympathetic tonus. The ratio of low-frequency to high-frequency powers was calculated as an index of sympathovagal interaction. RESULTS: When sleep deprived, the infants had an increase in basal heart rate during non-rapid eye movement sleep (P=.021). With sleep deprivation, the ratio of low-frequency to high-frequency powers increased in non-rapid eye movement sleep (P=.005). These findings were consistent with an increase in sympathetic tone. CONCLUSION: Infants exposed to short-term sleep deprivation manifest changes in cardiac autonomic controls during sleep. These findings could be relevant to mechanisms associated with the sudden infant death syndrome.     

Response to commentaries

The commentators on this article have provided valuable insight, support, or alternatives for the conclusions proffered in my position paper. They expand the spectrum of concepts and studies needed to provide further progress in understanding the observed clinical heterogeneity in AD. They also lend further support to the necessity for dialogue between basic and clinical scientists to urge this agenda ahead.     

Age-related changes in cardiac autonomic control during sleep

Aging is commonly associated with decreased sleep quality and increased periodic breathing (PB) that can influence heart rate variability (HRV). Cardiac autonomic control, as inferred from HRV analysis, was determined, taking into account the sleep quality and breathing patterns. Two groups of 12 young (21.1 +/- 0.8 years) and 12 older (64.9 +/- 1.9 years) volunteers underwent electroencephalographic, cardiac, and respiratory recordings during one experimental night. Time and frequency domain indices of HRV were calculated in 5-min segments, together with electroencephalographic and respiratory power spectra. In the elderly, large R-R oscillations in the very-low frequency (VLF) range emerged, that reflected the frequency of PB observed in 18% of the sleep time. PB occurred more frequently during rapid eye movement sleep (REM) sleep and caused a significant (P < 0.02) increase in the standard deviation of normal R-R intervals (SDNN) and absolute low-frequency (LF) power. With normal respiratory patterns, SDNN, absolute VLF, LF, and high frequency (HF) power fell during each sleep stage (P < 0.01) compared with young subjects, with no significant sleep-stage dependent variations. An overall decrease (P < 0.01) in normalized HF/(LF + HF) was observed in the elderly, suggesting a predominant loss of parasympathetic activity which may be related to decreased slow-wave sleep duration. These results indicate that two distinct breathing features, implying different levels of autonomic drive to the heart, influence HRV in the elderly during sleep. The breathing pattern must be considered to correctly interpret HRV in the elderly.     

Homeostatic changes in slow wave sleep during recovery sleep following restricted nocturnal sleep and partial slow wave sleep recovery during an afternoon nap

There has been speculation and some evidence to suggest that certain fractions of sleep, notably, slow wave sleep (SWS), are under homeostatic control. In order to test this hypothesis, the sleep of eight subjects was terminated on four different occasions after 50% of their normal baseline SWS levels had been obtained. An afternoon nap then followed during which 100%, 50%, or 25% of the SWS debt was reclaimed. A fourth condition contained no afternoon nap. The change in SWS from baseline during subsequent recovery sleep was directly related to the outstanding SWS debt, thus demonstrating that SWS is under homeostatic control.     

Experience-dependent changes in cerebral activation during human REM sleep

The function of rapid-eye-movement (REM) sleep is still unknown. One prevailing hypothesis suggests that REM sleep is important in processing memory traces. Here, using positron emission tomography (PET) and regional cerebral blood flow measurements, we show that waking experience influences regional brain activity during subsequent sleep. Several brain areas activated during the execution of a serial reaction time task during wakefulness were significantly more active during REM sleep in subjects previously trained on the task than in non-trained subjects. These results support the hypothesis that memory traces are processed during REM sleep in humans.     

ERP and behavioral changes during the wake/sleep transition

Event-related potentials (ERPs) following infrequent and frequent stimuli were studied as subjects moved from wakefulness to sleep. Subjects were instructed to respond to the infrequent “target” stimuli (attend condition) or to ignore the stimuli (ignore condition). Parietal P300, prominent following target ERPs in wakefulness under the attend condition, disappeared in association with reduced behavioral responsiveness and emergence of a central negativity (N350). The N350 and preceding and following positivities (P220 and P450) became the dominant feature of both target and nontarget ERPs under both attend and ignore conditions. The P220-N350-P450 complex was larger and peak latencies were shorter under the attend condition. Peak amplitudes tended to be larger following targets, especially under the attend condition. The findings suggest that, although the processes under-lying P300 are less likely to be engaged, processing of stimulus deviance and task relevance continues in sleepiness and sleep, and is reflected by variance in N350 and related activity.     

Exposure to relaxing words during sleep promotes slow-wave sleep and subjective sleep quality

Our thoughts alter our sleep, but the underlying mechanisms are still unknown. We propose that mental processes are active to a greater or lesser extent during sleep and that this degree of activation affects our sleep depth. We examined this notion by activating the concept of “relaxation” during sleep using relaxation-related words in 50 healthy participants. In support of our hypothesis, playing relaxing words during non-rapid eye movement sleep extended the time spent in slow-wave sleep, increased power in the slow-wave activity band after the word cue, and abolished an asymmetrical sleep depth during the word presentation period. In addition, participants reported a higher sleep quality and elevated subjective alertness. Our results support the notion that the activation of mental concepts during sleep can influence sleep depth. They provide a basis for interventions using targeted activations to promote sleep depth and sleep quality to foster well-being and health.     

468例癫癎患者睡眠期癎样放电与睡眠结构变化分析

目的：观察癫 患者的睡眠时相与 样放电的关系,并初步探讨癫 异常脑波活动对睡眠的影响。方法：对４６８例癫　患者进行２４小时动态脑电图（ＡＥＥＧ）监测,观察发作间期清醒与睡眠脑电图　样放电的发作频率,分析５８例癫　患者及对照组睡眠脑电图中睡眠时程、觉醒次数、睡眠纺锤波的变化。结果：４６８例患者中出现　样放电３６２例,睡眠期　样放电检出率８８％,觉醒期检出率５８％。样放电主要出现于ＮＲＥＭ睡眠Ⅰ－Ⅱ期。与对照组比较,癫　组ＮＲＥＭ　Ⅰ－Ⅱ睡眠期延长,ＮＲＥＭ Ⅲ－Ⅳ期缩短;觉醒次数增加,觉醒次数与　样放电频率呈正相关;并有睡眠纺锤波减少及不对称。结论：癫　患者的　样放电主要出现于ＮＲＥＭ睡眠Ⅰ－Ⅱ期,癫　活动对睡眠有一定影响,癫　患者睡眠质量下降。     

The boundary between wakefulness and sleep: quantitative electroencephalographic changes during the sleep onset period.

Microstructural electroencephalographic changes during the wakefulness-sleep transition have been investigated by comparing two definitions of sleep onset: the first occurrence of stage 1 and of stage 2. Power values were calculated across a 1-28-Hz frequency range in a 1-Hz bin resolution in the sleep recordings of 26 normal subjects. Quantitative changes were assessed after averaging individual time series, aligned with respect to the first occurrence of stage 1 or of stage 2.The time course of the single-Hz activity revealed a linear increase of power in the 1-6-Hz range and a linear decrease in the 9-12- and 16-28-Hz ranges during the stage 1 transition. During the stage 2 transition, electroencephalogram power linearly increased in the 1-7- and 14-15-Hz ranges and decreased in the 18-28-Hz range, while the 8-12-Hz range fitted a second-order polynomial curve. The two 'switch' points were also compared in their ability to differentiate Hz by Hz wakefulness from sleep: a lower mean power was found after stage 1 onset in the 9-11-Hz and 20-28-Hz bins and a higher one in the 1-5-Hz bins, while a higher power was found in the 1-8-Hz and 12-16-Hz bins and a lower one in 18-28-Hz bins after stage 2 onset. The time course of three electroencephalographic frequency ranges [delta/theta/sigma (1-7 and 12-16 Hz); beta (17-28 Hz); alpha (8-11 Hz)], grouped on the basis of a principal component analysis, fitted a first-order polynomial curve for the first two ranges, and a second-order polynomial curve for the last, with a progressive decrease during wakefulness, a minimum point during stage 1, and a subsequent increase during stage 2.The uniformly increasing electroencephalographic power across the 1-16-Hz frequency range during stage 2 and the shift of functional meaning for the alpha power during stage 1 point to the start of stage 2 as a more reliable boundary between wakefulness and sleep.     

Arterial pressure and heart rate changes during natural sleep in rat

Mean arterial pressure and heart rate data during quiet wakefulness and phases of sleep in conscious rat are sampled by a computer at a rate of 100/sec. Average values and variability expressed as standard deviation are computed for each recording session. Mean arterial pressure and heart rate and their variability decrease from quiet wakefulness to synchronized sleep. During desynchronized sleep, mean arterial pressure increases to the level of quiet wakefulness and is more variable than during synchronized sleep. Heart rate is lower and more uniform during sleep than during quiet wakefulness, and there is no difference between synchronized and desynchronized sleep except that a greater variability occurs during desynchronized sleep. The study shows that characteristic and specific cardiovascular changes accompany the phases of sleep and that a hierarchy of arterial pressure is present during the resting behavior in rat.