睡眠脑电的关联维数和近似熵分析

睡眠的正确分期是睡眠研究的基础,脑电的非线性参数可以表征不同的睡眠状态。本研究计算睡眠脑电的关联维数和近似熵,通过统计和比较发现关联维数不随嵌入维数的增加而饱和,但其相对大小能有效区分各种睡眠状态;近似熵计算简单,性能稳定,可较好地表征不同睡眠期;相对关联维数和近似熵从不同角度表现了脑电(大脑)复杂性的相同演变规律清醒时复杂性最高,而且波动最大,随着睡眠加深,复杂性降低且变异减小,REM期复杂性基本介于S1期和S2期之间。     

基于各物理因素对睡眠剥夺者脑电的影响

目的:研究不同的物理因素对被睡眠剥夺的受试者脑电的影响.方法:将24名成年健康男性随机分为四组,一个对照组和三个实验组,对所有受试者进行48 h睡眠剥夺实验,其中三个实验组在实验过程中分别不断接受音乐、磁场和局部高压氧干预措施,每个6 h提取一次受试者的脑电波数据.对睡眠脑电数据首先应用小波变换,将脑电信号中的噪声进行消噪处理,然后再利用近似熵和复杂度将消噪后的脑电信号进行特征提取和分析.结果:对于睡眠剥夺的不同时间段,其脑电近似熵的平均值随着脑疲劳程度的增加而降低.实验的前半部分受试者的脑电波的复杂度和近似熵没有统计学差异,但是实验的后半部分受试者的脑电波的复杂度和近似熵有了明显的区别.结论:不同的物理因素可以影响受试者的状态,从而影响受试者的脑电波.脑电近似熵随着脑疲劳程度的增加而降低,有望成为衡量脑疲劳程度的指标.     

基于能量特征和模糊熵的睡眠自动分期

目的:为实现有效睡眠自动分期,提出一种基于脑电能量特征和模糊熵的睡眠分期方法。方法:首先利用小波变换进行脑电信号去噪,再利用FIR带通滤波器提取脑电信号的特征波,获得能量特征,并提取脑电信号的模糊熵,最后利用支持向量机进行模式识别。结果:能量特征值和模糊熵值随着睡眠状态的变化而不同,睡眠各期可以根据特征值的不同而得到有效区分,通过对1 140个脑电信号样本进行睡眠分期,得到的平均准确率为88.45%。结论:基于脑电能量特征和模糊熵的睡眠分期方法简单、有效,具有良好的临床应用价值。     

基于近似熵的思维脑电信号分类研究

采用近似熵(approximate entropy，Apen)作为脑电信号的特征参数对不同思维作业脑电信号进行了分类研究，并对近似熵算法中参数的选择以及互近似熵在思维脑电分类的应用进行了讨探。研究结果表明，近似熵特征在思维作业脑电信号的分类中取得了较好的应用效果。近似熵作为EEG的信号特征为提高思维作业脑电信号的分类正确率提供了一种新的途径，在基于思维作业BCI的应用中具有重要的实用价值。     

不同思维状态下脑电近似熵的变化规律

背景:近似熵是一种描述信号复杂性和规律性的非线性动力学方法,只需较少数据就能度量信号的复杂性。目的:探讨不同思维状态下脑电近似熵的变化规律,以及近似熵在认知过程中的作用。方法:用近似熵对20名健康成年人在安静闭眼、安静睁眼、闭眼记忆、闭眼心算和图片识别5种状态下的脑电数据进行分析。结果与结论:近似熵值在闭眼计算和闭眼记忆思维状态高于安静闭眼状态,在图片识别状态下高于安静睁眼状态(P0.01);近似熵在安静闭眼和安静睁眼状态下各导联处于较低水平,在闭眼心算和闭眼记忆思维状态下各导联处明显增加。说明不同思维状态和不同导联部位对近似熵均有影响;近似熵在认知作业过程下较安静状态增高,并且不同思维状态下大脑功能活动的复杂性不同。因此脑电近似熵分析适用于认知过程脑功能活动变化规律研究,有助于了解大脑的工作机制。     

睡眠脑电信号的非线性动力学分析

睡眠与健康、工作、学习等之间的关系甚为密切。由于脑电(EEG)是描述睡眠过程中最显著和最直观的信号,所以睡眠脑电是研究睡眠的重要且有用的工具。其中睡眠分期研究对评估睡眠质量重要。由于脑电活动自身的复杂性,因此采用非线性方法处理会有比较好的结果。本文简单介绍了睡眠与脑电的关系,重点介绍了几种非线性动力学方法,包括李亚普诺指数、复杂度、相关维数、近似熵等,并介绍了它们对睡眠脑电信号进行特征处理的情况,发现在不同的睡眠期,计算出的结果呈现一定的变化规律。     

基于样本熵的睡眠呼吸暂停综合征脑电研究

目的:探讨睡眠呼吸暂停综合征(SAS)患者脑电的动力学特性,为SAS诊治提供依据。方法:基于脑电的非平稳和非线性特性,采用样本熵(Samp En)对6名SAS患者和6名健康人的睡眠脑电进行分析,研究SAS组和对照组在清醒、浅睡、深睡和快速眼动期(REM)的脑电变化及差异特性。结果:SAS患者和健康者睡眠脑电的样本熵变化有相同规律,即随着睡眠加深,其样本熵值均逐渐减小,但到REM期时,样本熵值又上升至觉醒期水平;与此同时,SAS组的样本熵值在各个睡眠阶段均低于健康组,两组间存在显著差异(P0.01);ROC曲线下面积达到0.858。结论:SAS病理状态对大脑神经活动影响显著,SAS组脑电样本熵值与对照组的显著差异为SAS研究及诊断提供新的方向和依据。     

严重意识障碍患者康复过程EEG非线性特征与CRS-R评分相关性分析与可视化表征

研究严重意识障碍患者意识康复过程脑电非线性特征与行为学意识量表CRS-R评分之间的相关性,并将非线性特征用于脑功能的可视化表征,为建立脑电非线性特征用于评估严重意识障碍患者意识康复过程提供电生理学依据。采集严重意识障碍患者(最小意识状态(MCS)10例和植物状态(VS)8例)意识康复过程中前后两次安静状态的脑电数据,计算近似熵、样本熵、排列熵和复杂度LZC等4种脑电非线性特征,对比分析非线性特征变化与CRS-R评分变化之间的相关性,并利用脑电地形图将近似熵非线性特征进行可视化表征。结果表明,MCS组和VS组CRS-R评分变化均为显著差异(P<0.01);MCS组的近似熵和复杂度LZC变化为显著差异(P<0.05),而VS组只有近似熵变化为显著差异(P<0.05);MCS组近似熵、复杂度LZC的变化与CRS-R评分变化的相关系数分别为0.851和0.693,呈显著正相关,VS组只有近似熵变化与CRS-R评分变化为显著正相关,相关系数为0.778;近似熵用于患者脑地形图可视化表征具有较好的效果。近似熵非线性特征用于评估严重意识障碍患者的意识康复过程具有一定的可行性。     

脑电信号的分析──一种探索大脑功能状态及活动规律的途径

本文从脑电产生的神经生理基础综述了脑电的发生及自发节律调控的不同学说和观点，从临床应用的角度综述了脑电图用于脑病诊断及在麻醉、睡眠研究中的应用，从脑电信号分析方面综述了相关分析、频域分析、时域分析等信号分析方法用于ＥＥＧ（Ｅｌｅｃｔｒｏｅｎｃｅｐｈａｌｏｇｒａｐｈ）信号处理的特点及存在的问题。最后本文介绍了时频分析、混沌方法及复杂性度量等脑电分析方法，这些方法将把脑电分析和研究向前推进一步，也有望成为探索大脑的思维、学习、感知等高级中枢活动规律的新手段。     

有关脑电地形图应用中的一些问题

有关脑电地形图应用中的一些问题吴雯珠１９８８年以来，国内生产脑电地形图（ＢＥＡＭ）机的厂家日益增多，购买ＢＥＡＭ机的医院在有的省普及到县级医院，使ＢＥＡＭ的临床应用与基础研究得到发展，成为一种新的医学诊断技术，但在使用中也出现一些问题。１电极数目ＢＥ...     

Recovery of Performance During Sleep Following Sleep Deprivation

Very few studies have systematically examined recovery of performance after sleep deprivation. In the present study, 12 young adult males were sleep deprived for periods of 40 and 64 hrs. Each period was preceded by baseline nights of sleep and followed by two recovery nights of sleep. Immediate recall and reaction time were tested at 2300, 0145, 0400, 0615, and 0830 during baseline, deprivation, and recovery nights. Performance efficiency showed a progressive decline after 2 hrs of recovery sleep following both periods of deprivation. Return to baseline was apparent after 4 hrs of steep following 40 hrs awake and after 8 hrs of sleep following 64 hrs awake. These results suggested that, in terms of behavioral efficiency, an equal amount of sleep is not required to compensate for sleep lost.     

Sleep Stage Deprivation and Total Sleep Loss: Effects On Sleep Behavior

The combined effects of total sleep loss and the deprivation of stage 4 or stage REM were studied in I two separate experiments. Two full nights or sleep loss preceded stage 4 deprivation or stage REM deprivation in Experiment 1 (N=12); 1 full night of sleep loss followed 3 nights or stage 4 deprivation or stage REM deprivation in Experiment 2 (N=I4). Total sleep loss before sleep stage deprivation significantly increased the number of attempts to enter stage 4, but had little influence on stage REM. A significant REM rebound was found in only one of the REM-deprived groups, but there was a significant stage 4 rebound in all groups on the first full recovery night, supporting the hypothesis from other studies that stage 4 has priority over REM in terms of recovery from sleep loss. The results suggested that stages 2, 3, and 4 partially overlap in their recuperative functions.     

Sleep During and After Gradual Sleep Reduction

To determine: 1) the minimum amounts of sleep subjects would tolerate, 2) the changes in EEG sleep measures, and 3) whether subjects would revert to baseline sleep after study termination, 4 couples gradually reduced their sleep. Three couples reduced their TST in 30-min steps from a baseline of 8 hrs and one couple from a baseline of 6.5 hrs. Subjective estimates of sleep time, sleep quality, and mood were collected daily. Home EEG sleep recordings were obtained 3 nights a week. Two of the 8-hr sleepers reduced their sleep to 5.5 hrs, 2 to 5.0 hrs, and 2 reached 4.5 hrs. These 6 subjects continued sleeping 1 to 2.5 hrs below baseline amounts a year after reduction terminated. The 6.5-hr baseline couple reached 5.0 hrs and returned to 6.5 hrs TST during follow-up. Stages W, 2, and REM decreased significantly in absolute amounts. Percentage of stages W and 2 also decreased significantly. REM percent remained constant. Stage 3 was constant while stage 4 increased in both absolute and relative amounts. REM cycle length remained constant. Stage 4 rebound on 7-hr nights was not observed during times of greatest sleep reduction. Occurrences of stage REM within 10 min of stage 1 onset were observed in 2 subjects when their TST was below 6.5 hrs. Our results are consistent with other studies of shortened sleep, indicating that TST is the major determinant of sleep-stage characteristics.     

Effects of Experimentally-Induced Sleep Fragmentation on Sleep and Sleepiness

The effects of two levels of sleep fragmentation on sleep and daytime sleepiness were investigated in young adult males. Experimental subjects were informed while awake that tones would be presented periodically throughout the night and that their task was to terminate the tone by taking a deep breath. Eight subjects received tones after each minute of sleep and 8 received tones after each 4 min of sleep. Control subjects (N=8) HI did not receive (ones. The subjects were tested for daytime sleepiness using the Multiple Steep latency Test. It was found that: 1) subjects responded reliably lo tones presented during sleep; 2) behavioral control was accompanied by brief electro-physiological indices of arousal on almost all trials, and occasionally led to fall awakenings; 3) sleep was markedly altered in the 1-min condition; 4) a relatively small effect on sleep (reduced stage 4 sleep) was produced by the 4-min condition, and 5) daytime sleepiness was increased by the 1-min condition but not the 4-min condition. It was concluded that the most parsimonious explanation of these results is (he Continuity of Sleep hypothesis.     

Body Movements During Sleep After Sleep Loss

Following 4 baseline nights, 7 Ss were deprived of REM sleep for 3 nights and 7 were deprived of stage 4 sleep. Both groups were then deprived of total sleep for 1 night and then allowed 2 nights of uninterrupted recovery sleep. Compared to baseline nights, on the first recovery night the number of body movements was significantly reduced in all sleep stages and for total sleep. On the second recovery night, the number of movements was back to baseline level. The increased amount of slow-wave sleep (stages 3 and 4) during recovery sleep was not the primary reason for the reduced body motility.     

Assessment of Sleep Hygiene Using the Sleep Hygiene Index

The Sleep Hygiene Index was developed to assess the practice of sleep hygiene behaviors. The Sleep Hygiene Index was delivered to 632 subjects and a subset of the subjects participated in a readministration of the instrument. Test–retest reliability analyses suggested that sleep hygiene behaviors are relatively stable over time for a nonclinical population. Results confirmed that sleep hygiene is strongly related to sleep quality and modestly related to perceptions of daytime sleepiness. As predicted, support of the sleep hygiene construct was also provided by strong correlations with the associated features of a diagnosis of inadequate sleep hygiene. The Sleep Hygiene Index, a much shorter sleep hygiene instrument than previously published, demonstrated comparable psychometric properties with additional evidence of validity and a clear item selection rationale.     

Sleep Patterns and Sleep Disruptions in Kindergarten Children

Assessed sleep patterns and sleep disruptions in kindergarten children and investigated the relation between sleep measures derived from objective and subjective evaluation methods. The sleep patterns of 59 normal kindergarten children (mean age = 5.5 years) were monitored for 4 to 5 consecutive nights by means of activity monitors (actigraph) and by means of parental daily sleep logs. The correlation between the actigraphic measures and the daily parental logs indicated that parents were accurate reporters of sleep schedule measures. However, parents were less accurate in assessing sleep quality measures, significantly underestimating the number of night-wakings and overestimating the quality of their children's sleep. Fragmented sleep was found, by means of activity monitoring, in 41% of the children.     

Effects of Sleep Deprivation on Memory and Sleep Latencies in Connection with Repeated Awakenings From Sleep

Twelve subjects were kept awake 64 hrs. During baseline and recovery sleep, subjects were given a simple memory task. The subjects were awakened 3 times each night during slow-wave sleep and shown 4 playing cards. Approximately 90 min later the subjects were again awakened and tested for retention of the previous cards and given 4 new cards to learn. This procedure was repeated 3 times each night and upon awakening the following morning. On the recovery night recall was reduced, slow-wave sleep was lengthened, sleep latency was shortened, and body motility was reduced. It was suggested that the reason for the poorer recall was deeper sleep induced by the sleep deprivation.