应用小波熵分析大鼠脑电信号的动态变化特性

应用小波熵（一种新的信号复杂度测量方法）分析大鼠在不同生理状态下脑电复杂度的动态时变特性。采用慢性埋植电极记录自由活动大鼠的皮层EEG,使用多分辨率小波变换将EEG信号分解为δ、θ、α和β四个分量,求得随时间变化的小波熵。结果表明：在清醒、慢波睡眠和快动眼睡眠三种生理状态下,EEG的小波熵之间存在显著差别,并且在不同时期其值与各个分解分量之间具有不同的关系,其中,慢波睡眠期小波熵还具有较明显的变化节律,反映了EEG微状态中慢波和纺锤波的互补性。由此可见,小波熵既能区别长时间段EEG复杂度之间的差别,又能反映EEG微状态的快速变化特性。     

局灶性脑缺血损伤无创检测中EEG近似熵研究

局灶性脑缺血的早期无创诊断在临床实际中有着非常重要的意义。采用SD（Sparague-Dawley)大鼠建立了局灶性脑缺血的动物实验模型,记录了缺血前后缺血区域和正常区域的脑电信号EEG。由于近似熵复杂度算法所需时间序列长度较短,大大减少了脑电信号非平稳所带来的困难,且无需粗粒化,采用近似熵对局灶性缺血动物实验模型的脑电信号的复杂度进行了分析。结果发现缺血前后缺血与非缺血区域的近似熵均有着易于区分的特征,因此EEG信号的近似熵分析可以用于对局灶性缺血的脑损伤程度进行诊断,并区分损伤区域和非损伤区域,有望在临床中加以应用。     

40例慢性脑型血吸虫病的脑电图分析

目的:了解脑型血吸虫病脑电图(EEG)的脑电活动状况,为临床诊断与治疗提供参考。方法:收集1997~2004年临床诊断为脑型血吸虫病的40例EEG资料,主要分析异常EEG的脑电活动状况与异常程度、临床分型及预后的关系。结果:31例出现不同程度的EEG异常改变,异常率为77.5%,其中癫痫性为70%;脑瘤型为100%。绝大部分EEG检查是患者经治疗后作的。治疗前后均作了EEG检查的仅9例。治疗前,9例均有不同程度异常,治疗后7例有不同程度改善,2例恢复正常。结论:EEG对脑型血吸虫病的诊断及预后的评价有参考价值。     

额叶EEG偏侧化预测情绪灵活性

随着社会竞争的日益加剧,人们在生活、学习、工作中都可能遇到各种与情绪有关的事件,如何根据情境的要求和个人的需要对情绪进行灵活性的反应,对每个人而言都至关重要.情绪灵活性的研究已成为情绪心理学、临床心理学、健康心理学等多个领域热衷讨论的课题.研究发现,左侧和右侧前额叶皮层半球不同程度地涉及加工和调节对情绪刺激的情绪反应,因此,额叶脑电图(EEG)偏侧化与情绪灵活性存在密切关系.但是,额叶EEG偏侧化是否是情绪灵活性的一个客观指标,以及额叶EEG偏侧化怎样预测情绪灵活性,至今仍不清楚.本研究测量了通过情绪电影范式诱发被试产生高兴、悲伤、愤怒、恐惧、厌恶等情绪过程中的额叶EEG活动.结果显示,情绪灵活性的激活模式反映的是情绪的动机维度,而不是情绪的效价维度.在静息状态下,对于与接近动机相关的情绪,额叶EEG左侧化的个体的左侧化程度增加;对于与回避动机相关的情绪,其左侧化程度降低.与之相对,静息状态额叶EEG右侧化的个体,无论对于与趋近动机相关的情绪还是与回避动机相关的情绪,额叶EEG偏侧化的程度没有发生改变.研究表明,额叶EEG偏侧化模式能够预测情绪灵活性,额叶EEG左侧化的个体有更灵活的情绪反应,额叶EEG右侧化的个体则有相对不灵活的情绪反应.     

急性缺氧和缺氧习服对鼠足冻伤组织存活面积的影响

本工作观察了急性缺氧和缺氧习服对Ｗｉｓｔａｒ大鼠左后足冻伤组织存活面积的影响。急性缺氧冻伤组和平原冻伤组大鼠冻足ＴＳＡ分别为５７．６８％、６０．２５％和６７．７７％、６６．８８％,损伤程度基本相同,表明大鼠模拟６０００ｍ高度急性缺氧８ｈ不加重冻伤引起的组织损伤。大鼠模拟６０００ｍ高度减压缺氧习服１４ｄ或２８ｄ后再作－１５℃或－２０℃冻伤,冻足ＴＳＡ仅为１４、８４％－２３．９１％,明显少于急性缺氧冻     

30例急性血吸虫病的脑电图分析

本文报道了30例急性血吸虫病的脑电图(EEG）资料分析。其中25例异常(占83．3％),主要表现为a波慢化、不规则或基本节律消失。25例中22例(占88％)的慢波以低。中波幅不规则θ波为主,分布以双侧中央区为多,额、枕区次之。EEG异常者,与病情严重程度相关,病情严重者EEG异常程度相对高。12例经治疗后,11例EEG有所改善。     

重复脑缺血对缺氧耐受性的影响

防治脑血管疾病的一个主要策略是提高脑细胞对缺氧的耐受能力,其措施之一是反复进行缺氧适应,使之获得高度耐受性。本工作在已建立的家兔脑缺血模型上反复进行脑缺血适应,比较动物脑缺血适应前后呼吸频率、存活时间以及脑诱发电位的变化,借以了解重复脑缺血对缺氧的耐受性影响。     

抽动障碍临床特点与脑电图关系的研究进展

抽动障碍(Tic disorder,TD)是一种儿童期发病且主要侵犯神经系统的疾病。临床工作中发现部分患儿脑电图(electroencephalogram,EEG)明显异常,提示患儿脑功能障碍与疾病严重程度有关;TD患儿治疗后EEG变化特点也对临床医生选择何种治疗方式有指导意义。     

慢性缺氧对两种不同敏感性大鼠肺动脉压和右心功能的影响

将国外引进繁殖的“缺氧敏感大鼠”(Hilltop SD)和国内常用的实验大鼠(Wistar)同时放在模拟5000米高度的低压舱内进行慢性缺氧,(分平原对照和缺氧4、10、20、30、40天六组),发现HT大鼠的肺动脉压升高程度明显大于W大鼠。在缺氧20天以内,随着肺动脉压的升高,两种大鼠右室心肌收缩性能指标[ dp/dt_(max),( dp/dt_(max)(/RVSP)和舒张性能指标[-dp/dt_(max),(-dp/dt_(max)/RVSP]相应增加。但HT大鼠的心脏代偿功能比W大鼠好。缺氧30天以后,上述心肌性能指标均有下降趋势。关于HT大鼠与W大鼠对缺氧敏感性的差异原因尚待进一步研究。     

基于高阶复杂性测度的心率变异信号分析

心率变异性反映了交感神经和迷走神经对心血管系统的综合调节作用,是评价心血管系统功能的重要指标。复杂度是描述时间信号序列信息量的一个重要参数,传统算法中的过分粗略化会丢失大量的有用信息,而高阶复杂度的引入可较大程度地避免这一问题。在利用Lorenz模型数据仿真的基础上,分别对25例正常人样本和25例充血性心力衰竭病人样本的心率变异信号的1～15阶Kolmogorov复杂度进行了计算,通过对比分析后确定,5阶Kolmogorov复杂度在临床医学上可以为分析心率变异信号获得更为理想的效果。     

Characteristics of the human EEG during cognitive-mnemenic activity under hypoxic conditions

The amplitude-frequency and spatiotemporal characteristics of the EEGs of subjects performing various cognitive-mnemenic activities under the conditions of graduated hypoxia were studied. The quickness and correctness of test performance were significantly decreased beginning from the sixth minute of hypoxia as compared to normoxic conditions. The amplitude and mean period of the dominant EEG activity in this functional state were higher than in the same tests performed under normoxic conditions and lower than in the case of hypoxia not accompanied by the performance of tests. The spatiotemporal characteristics of the EEG under hypoxic conditions displayed both the characteristics typical of hypoxia (a decrease in EEG cross-correlation within anterior cortical regions) and those typical of cognitive-mnemenic activity (an increase in the correlation between the EEGs of distant zones of anterior and posterior cortical regions). It is assumed that the “intermediate” EEG pattern observed in subjects performing cognitive-mnemenic tests under hypoxic conditions reflects opposite effects of hypoxia and intellectual effort on the functional activity of brain neurons.     

Individual typological features in the EEG of athletes after acute hypoxic treatment

In athletes with different types of physical training and various temperaments, variability of the main rhythms of the EEG (??, ??, and ??) and the parameters of the desynchronization response of the ??-rhythm, the individual extent of the decrease in the power of the ??-rhythm during eye opening under the conditions of hypoxia growing from 20.9 to 10% of O₂ were studied. Twenty-four 18- to 26-year-old athletes, including 11 swimmers and 13 skiers, were involved in the study. We found that, in contrast to normoxia conditions, hypoxia was associated with the instability of the spectrum of the EEG rhythms and phasic changes during a 25-min hypoxia. The EEG response during hypoxia depended on individual typological features estimated using Strelau??s temperament questionnaire. Negative correlation between the psychological construct ??endurance?? measured using the FCB-TI questionnaire (Formal Characteristics of Behavior-Temperament Inventory) and the power of the EEG ??-rhythm was found. The parameters of training and the features of the respiration pattern that appeared as a consequence of training modulated the sensitivity of brain structures to hypoxia, which was reflected in the changes in the EEG ??-rhythm under hypoxia conditions.     

Electroencephalograms and cerebral blood flow in carp, Cyprinus carpio, subjected to acute hypoxia

Changes in electroencephalogams (EEG) and cerebral blood flow were examined in carp immobilized with a muscle relaxant during 60 min hypoxia (water Po ₂ of approximately 20 mmHg) and subsequent 30 min normoxia. The amplitude of EEG waves recorded from the telencephalon decreased gradually but slightly with the progression of hypoxia, whereas the telencephalic blood flow increased mainly due to an increased blood velocity. These findings suggested that cerebral activity during hypoxia was compensated to some degree by increased cerebral blood flow. However, carp showed large variations in the patterns of EEG responses and cerebral blood flow.     

EEG markers of the disturbed systemic brain activity in hypoxia

Specific rearrangements of the brain bioelectric potential field and the structures where the components (waves) of the main EEG rhythms interact, as well as the stereotactic location and power of the equivalent electrical dipole sources (EEDSs), were studied at various stages of acute experimental hypoxia (breathing for 15–30 min a hypoxic gas mixture containing 8% oxygen in nitrogen). The disrupted intercentral relationships that ensure the formation of the dynamic “morphological equivalent” to support the integrative brain activity, rearrangements of this activity, and the adaptive functions of the whole brain proved to account for partial or complete disintegration of systemic brain activity during acute hypoxia. EEDS tomography showed that EEDSs responsible for the generation of the basic brain rhythmic pattern are normally located in the thalamic structures. At the initial stages of hypoxia, the distribution of the EEDS foci is changed so that the density of EEDSs is increased on the sections that include the hypothalamic region structures, basal nuclei of the forebrain, and the limbic system; the basal, frontal, and medial regions of the temporal lobes of both hemispheres are also involved. With increasing hypoxia, EEDSs appeared in the basal and medial regions of the frontal lobes. At this time, both the surface and deep regions of the frontal lobes of the brain hemispheres are the major targets of the hypoxic effect. At the stages of severe hypoxia, pronounced functional changes in the CNS are observed, including the phenomenon of movement of multiple EEDS foci primarily through the basal and mediobasal regions of the frontal and temporal lobes and in the limbic system structures. Thus, despite the generalized high-amplitude paroxysmal activity that is observed in EEG, a functional disintegration (disruption) of interactions between individual brain regions appears and leads to disturbed regulation of the brain and systemic brain activity. Spatiotemporal EEG markers have been identified that make it possible to assess the individual sensitivity and resistance to hypoxia, as well as the degree of disintegration of his systemic brain activity at different stages of hypoxia.     

Effect of high altitude hypoxia on the human EEG

The paper presents the results of the comparative study of the EEG at alpine altitudes (Tuya -- Ashu pass, 3200 m) and at low altitudes (City of Frunze, 760 m above the sea level). The dynamics of EEG changes at different stages of adaptation to hypoxia is also traced. The obtained data show that the alpine hypoxia produces a considerable intensification of the excitation processes in the cerebral cortex. Different sensitivity to the oxigen shortage has been found in the frontal-temporal parts of the right and the left hemispheres.     

Changes of external respiration, brain circulation and the EEG in acute hypoxia in the subjects with different hypoxic resistance

Two groups of individuals were distinguished in experiments with acute hypoxic action (respiration of oxygen-nitrogen mixture with 8 % oxygen content) - with low (LHR) and high (HHR) resistance to hypoxia. In subjects of the LR group, slowing down of the pulse rate and lowering of arterial pressure in the shoulder artery were observed on the 5th-10th minute of hypoxia. In the HHR subjects, primary growth of the pulse rate was followed by its stabilization; no significant changes of the arterial pressure were observed. In LHR subjects, in the first 5-10 min of the hypoxia, a significantly lower level of the blood oxygen saturation was observed in comparison to the HHR. In the LHR group, there was a higher increment of amplitude-frequency index of the rheoencephalogram in comparison to the HHR, indicating a higher increment of the cerebral blood flow. The slowing down of the pulse rate in the LHR subjects was accompanied with increasing cerebral pulse volume, so that in spite of the pulse rate slowing, the minute volume of cerebral circulation increased. In the LHR subjects, two-phased dynamics of the EEG was observed: in the first phase there was a slow growth of theta- and delta-band EEG spectral power, in the second phase (on the 5th-10th min of hypoxia), sharp (200-300 % of the background level) growth of the EEG spectral power in those bands was observed. In the HHR subjects, gradual growth of EEG spectral power occurred with relative stabilization on the 10th-12th min of hypoxia. Possible role of the stress in the collapse-like reaction during acute hypoxia is analysed, which might cause increase of the oxygen request of the brain, higher growth of cerebral blood flow and more pronounced lowering of functional activity of the brain in the LHR subjects.     

急性重复缺氧对大鼠海马电活动的影响

本实验以大鼠喘呼吸的出现为重复缺氧时每次缺氧耐受极限（下次缺氧开始的标志）,观察重复缺氧对海马ＣＡ１、ＣＡ３区群锋电位（ｐｏｐｕｌａｔｉｏｎｓｐｉｋｅ,ＰＳ）及海马脑电图的影响。结果表明,首次缺氧早期,刺激同侧隔区所诱发ＣＡ１和ＣＡ３的ＰＳ幅值无明显变化。随着缺氧程度的加深,ＣＡ１和ＣＡ３的ＰＳ幅值逐渐降低,ＣＡ１－ＰＳ于缺氧８ｍｉｎ时消失,此时ＣＡ３－ＰＳ为缺氧前的６０％;海马脑电图θ慢波的波幅和频率也随着缺氧的加深而降低。随着缺氧重复次数的增加,耐受时间逐次延长,ＣＡ１－ＰＳ和ＣＡ３－ＰＳ幅度均逐次降低,到第４次缺氧时,维持在很低水平。ＣＡ１－ＰＳ于缺氧１４ｍｉｎ时消失,此时ＣＡ３的ＰＳ为缺氧前的５％,缺氧１６─１８ｍｉｎ时ＣＡ３－ＰＳ才消失;ＣＡｌ区海马脑电图经常表现为自发性放电,而ＣＡ３区则表现低幅低频慢波。结果提示,重复缺氧时缺氧耐受性的逐次增高与海马电活动逐次抑制相关,重复缺氧使海马ＣＡ１、ＣＡ３区缺氧耐受性差异增大。     

Relations of the EEG local and spatialtemporal spectral characteristics changes under hypoxia in humans

Spatial temporal and local EEG characteristics were studied in healthy subjects during inhalation of hypoxic oxygen-nitrogen gas mixture with 8 % content of oxygen. Analysis of spectra power density, coherence, phase shift, similarity of dominant frequencies in the EEGs of different derivations was performed separately for the EEG epochs with and without visually detected patterns of spatial synchrony of the EEG. Apart from this, a fact of dominance of the frequency in the EEG spectra of corresponding derivation was taken into account when estimating spectral parameters. Results of the study showed that, in general, under hypoxia, the EEG coherence in alpha- and delta-frequency range decreases as compared to the background level, in beta-range growth of this parameter is observed, in theta-range ambiguous changes occur: in the epochs with patterns of spatial synchrony--growth, in other epochs--lowering. Under hypoxia, also occurs growth of frontal and temporal EEGs' phase shift (corresponding to EEGs other derivations) in delta- and theta-range. In beta-range, on the contrary, average level of the phase shift decreases. It was revealed that taking into account the fact of dominance of frequency in the local EEG spectra is necessary for correct interpretation of the EEG spatial and temporal parameter analysis' results. A mathematical model of interaction between processes with different frequency characteristics is suggested, which explains some facts obtained in the study.     

Free Fatty Acids in the Rat Brain in Moderate and Severe Hypoxia

Abstract: The effects of mild, moderate, and severe hypoxia on cerebral cortical concentrations of free fatty acids (FFAs) were investigated in artificially ventilated rats under nitrous oxide anaesthesia. No change occurred during either mild (arterial Po₂ 35–40 mm Hg) or moderate (Po₂ 25–30 mm Hg) hypoxia. The effects of severe hypoxia (Po₂ about 20 mm Hg) combined with hypotension (mean arterial blood pressure 80–85 mm Hg) varied with the EEG pattern and the tissue energy state. Thus, a major increase in total as well as in individual FFAs occurred first when EEG was severely depressed (almost isoelectric) and energy homeostasis disrupted. On a relative basis the greatest change occurred in free arachidonic acid. It is concluded that hypoxia is associated with an increase in the concentrations of FFAs in brain tissue, provided that tissue oxygen deficiency is severe enough to cause tissue energy failure. However, an increase in FFAs does not invariably accompany minor reductions in the adenylate energy charge (EC) of the tissue.     

Selected Contribution: Regulation of sleep-wake states in response to intermittent hypoxic stimuli applied only in sleep.

Recurrent sleep-related hypoxia occurs in common disorders such as obstructive sleep apnea (OSA). The marked changes in sleep after treatment suggest that stimuli associated with OSA (e.g., intermittent hypoxia) may significantly modulate sleep regulation. However, no studies have investigated the independent effects of intermittent sleep-related hypoxia on sleep regulation and recovery sleep after removal of intermittent hypoxia. Ten rats were implanted with telemetry units to record the electroencephalogram (EEG), neck electromyogram, and body temperature. After >7 days recovery, a computer algorithm detected sleep-wake states and triggered hypoxic stimuli (10% O2) or room air stimuli only during sleep for a 3-h period. Sleep-wake states were also recorded for a 3-h recovery period after the stimuli. Each rat received an average of 69.0 +/- 6.9 hypoxic stimuli during sleep. The non-rapid eye movement (non-REM) and rapid-eye-movement (REM) sleep episodes averaged 50.1 +/- 3.2 and 58.9 +/- 6.6 s, respectively, with the hypoxic stimuli, with 32.3 +/- 3.2 and 58.6 +/- 4.8 s of these periods being spent in hypoxia. Compared with results for room air controls, hypoxic stimuli led to increased wakefulness (P < 0.005), nonsignificant changes in non-REM sleep, and reduced REM sleep (P < 0.001). With hypoxic stimuli, wakefulness episodes were longer and more frequent, non-REM periods were shorter and more frequent, and REM episodes were shorter and less frequent (P < 0.015). Hypoxic stimuli also increased faster frequencies in the EEG (P < 0.005). These effects of hypoxic stimuli were reversed on return to room air. There was a rebound increase in REM sleep, increased slower non-REM EEG frequencies, and decreased wakefulness (P < 0.001). The results show that sleep-specific hypoxia leads to significant modulation of sleep-wake regulation both during and after application of the intermittent hypoxic stimuli. This study is the first to determine the independent effects of sleep-related hypoxia on sleep regulation that approximates OSA before and after treatment.