基于复杂性测度的光诱发下alpha波脑电特性研究

目的:利用Lempel-Ziv复杂度算法,研究光诱发下α波脑电特性。方法:记录20名正常受试者(平均年龄23.2岁)在闭眼状态下接受12 Hz闪光刺激的脑电信号,分析光刺激前后α波脑电复杂度变化。结果:发现12 Hz光刺激能够引起17名受试者α波脑电复杂度的显著增加(P<0.05);其中在额部、右中央、顶部、枕部、右中颞、左右后颞α波脑电复杂度变化较为显著,以顶部与枕部变化最为明显;光刺激后,左右半脑平均α波复杂度均出现增加,其中右脑区α波复杂度变化更为显著。结论:12 Hz频率光诱发能够引起同频率段的脑波信号的显著响应,该结论有助于研究光诱发下的脑功能特性,且对于探索外部刺激对人脑认知活动的影响具有参考价值。     

不同认知深度下大脑α波同步变化规律研究

以能体现不同认知深度的视觉图形为刺激源,以归一化香农熵作为稳态视觉诱发电位（SSVEP）的α波与刺激信号相位同步的有效评测指标,受试者识别视觉图像的正确率为认知精度,刺激频率为7~15 Hz,刺激强度为强、中、弱（分别对应屏幕最大亮度的100%、50%、0%）,实验研究认知深度与SSVEP的α波的相位同步程度之间的变化关系。结果表明:（a）在本文研究范围内,无论刺激强度为强、中、弱,深度认知对应的α波同步程度最大,其次是中度认知的,浅层次认知对应的同步程度最小;（b）刺激强度一定时,3种不同认知深度下的α波同步程度在大脑自发α波频率处（IAF, 约为10 Hz) 最大,随着刺激频率与IAF差值绝对值的增加,同步程度逐渐下降,呈现非线性同步理论中阿诺德舌头变化规律;（c）在中、低刺激强度下,当刺激强度一定时,认知精度随刺激频率和IAF差值绝对值的增加而呈现阿诺德舌头变化规律（中心频率为IAF）,此外,在中等刺激强度,13 Hz处也呈现较高的认知精度。不过,当刺激强度超过一定阈值时,认知精度出现明显下降趋势,提示过高的视觉强度将影响认知精度大小。本结果为研究认知活动的潜在作用机制和大脑认知功能障碍的诊断与治疗提供了新思路。     

基于不同闪烁频率光刺激的脑电压变化研究

目的：脑电信号是大量神经元电活动在大脑头皮表面产生的电位总和,可综合反映大脑内部功能状态和活跃程度。当人体受到外界刺激时,神经系统产生一系列复杂的生物电活动,最终反映为脑电信号。本文使用不同闪烁频率光为刺激源,对光刺激前后脑电信号时域和频域的变化特性进行分析,为利用外刺激调制脑电频率提供新的实验依据。方法：使用同一光源,分别改变其闪烁频率对受试者眼睛进行刺激,利用脑立方移动版采集不同闪烁频率光刺激下的脑电信号,记录并分析脑电信号电位幅值,及其成份δ波（1 Hz~3 Hz）、θ波（4 Hz~7 Hz）、α波（8 Hz~13 Hz）和β波（14Hz~30Hz）能量的变化情况。结果：随着光闪烁频率的增高,脑电压幅度均值和各频段能量先逐渐增大后减小,脑电幅值和各频段能量均在光闪烁频率为5 Hz时达到最大。结论：不同闪烁频率光刺激对脑电压的变化具有显著性影响：在一定阈值之下,脑电压与光闪烁频率变化一致;超过阈值后,趋势相反。该结论有助于探索脑电信号在外刺激作用下的变化规律,为利用外刺激治疗脑部疾病的方式提供了参考价值。     

基于磁刺激内关穴的脑电α波时频分析

目的 本文将磁刺激和传统中医穴位、经络传导相结合,研究了磁刺激内关穴对大脑α波的分布及能量的影响.方法 绘制不同状态下的α波分布的脑电地形图,分析磁刺激对大脑α波分布的影响.采用Gabor小波和希尔伯特变换方法研究磁刺激对大脑α波能量的影响.结果 磁刺激内关穴能够引起被试者α波的分布及能量的变化,表现在：磁刺激时α波分布范围大于安静状态;与刺激前相比,磁刺激后大脑额叶和左侧枕叶的α波能量明显增强.结论 本研究表明磁刺激被试者的内关穴可能使被试者达到清醒和镇定的状态,与针刺内关穴的安神醒脑作用有着异曲同工之效.本研究验证了磁刺激穴位的有效性,为今后的相关研究奠定了基础.     

一种新的电子耳蜗的刺激脉冲序列的合成方案

现有的电子耳蜗的刺激脉冲序列的合成方案都是以固定频率和位置编码方式刺激听觉神经纤维来诱发听觉。但是，这些合成方法破坏了语音信号的时间上的相关性和相干性，均不能反映人的耳蜗对语音信号的时间编码方式。本研究提出了一种全新的刺激脉冲序列的合成方案，该方案能够在语音信号的小波变换域上的过零点处产生刺激脉冲合成脉冲序列，我们将之称为小波一过零刺激方案。小波一过零刺激方案可有效地克服电极之间的相互影响，同时刺激脉冲序列的时间间隔完全由语音信号的动态特性确定，从而保证了语音信号的时间相关性和相干性。     

磁刺激神门穴脑电信号的样本熵分析与诱发电位的研究

研究用经颅磁刺激仪在不同频率下刺激肢体神门穴,在安静、磁刺激、假刺激、假穴4种不同状态下脑电信号的样本熵值以及脑电信号诱发电位的特征。对8名被试者进行实验,实验分为4组即安静、磁刺激、假刺激、假穴,测量3种不同频率(0.5、1、3 Hz)刺激下的脑电信号并计算样本熵值,对刺激后的脑电信号诱发电位进行了分析。结果显示,1 Hz与0.5 Hz磁刺激脑电信号样本熵没有明显变化(P0.05);3 Hz时4种状态下的脑电信号样本熵变化较明显(P0.05),磁刺激组和假穴组明显高于安静组和假刺激组,且磁刺激组略低于假穴组;3 Hz磁刺激无诱发电位;而假穴组产生明显体感诱发电位等其他诱发电位。实验表明,对人体神门穴进行磁刺激对脑电信号有明显抑制,与进行针刺或电刺激同样具有调节神经机能的作用。     

不同电刺激信号对大鼠雪旺细胞增殖的影响

目的研究不同的电刺激信号对大鼠雪旺细胞(RSC96)增殖的影响。方法实验使用RSC96细胞系(中国科学院典型培养物保藏委员会细胞库),经过2次传代培养,以1.25×10~4/孔的密度种植于24孔细胞培养板中,次日电刺激信号分别采用不同的电压(10、100、500、1 000、5 000、10 000 m V/cm)、不同的频率(0.1、1.0、100.0、1 000.0、10 000.0、1 000 000.0 Hz)、不同的脉冲占空比(5%、10%、30%、50%、70%、90%)及不同的波形(正脉冲波、矩形波、三角波、正弦波、杂波、直流波)对细胞进行电刺激,每组设置3个平行样,细胞每天刺激30 min,持续刺激4 d。采用四甲基偶氮唑盐(MTT)法检测细胞增殖率。结果当电刺激频率为100.0 Hz、脉冲占空比为50%、波形为矩形波时,电压500 m V/cm时对细胞的增殖具有抑制作用。当电刺激频率为100.0 Hz、脉冲占空比为50%、电压为500 m V/cm时,正脉冲波、正弦波、矩形波和三角波都能够促进细胞的增殖。当电刺激波形为矩形波、脉冲占空比为50%、电压为500 m V/cm时,频率100.0~1 000.0 Hz组细胞增殖率最高。当电刺激波形为矩形波、频率为100.0 Hz、电压为500 m V/cm时,不同的脉冲占空比对细胞增殖的影响不明显。结论不同的电刺激信号条件对细胞增殖的影响较大。电压≤500 m V/cm、有规律的脉冲波形、频率为100.0~1 000.0 Hz电刺激信号能够获得较好的RSC96增殖的效果。实验所获得的优化电刺激参数在外周神经修复中具有非常大的应用前景。     

大脑皮层信号作用下人体步态节律运动的探讨

节律运动是由中枢模式发生器自激产生的。目前的中枢模式发生器(CPG)建模研究仅表现了CPG的自激行为,对于人脑信号的调节性并没有涉及。本研究提出了基于Matsuoka神经振荡器的CPG模型的修正模型,目的在于以这一修正模型体现大脑皮层信号对于CPG网络的调控性。通过对原有模型中输入刺激与网络内部参数的复杂关联的构建,使得模型本身各参数随输入信号的变化而变化,增强了输入信号对于网络自身的影响,令网络不局限于自激状态,还能够产生自我调节的运动形式,从而体现出大脑信号的调控作用。数值模拟计算结果表明,修正后的模型随着输入刺激的变化可以产生不同模式及不同频率的运动形式,且各不同形式之间可以相互转换,从而在理论上很好地反映出大脑信号在步态节律运动过程中,对步态的模式和频率所起到的一定的调节作用,实现了各种步态运动之间的行为转换及恢复的功能,从理论上实现了自发节律与大脑调节性节律运动的共存性,做到大脑信号与CPG模型的统一。     

α频率光刺激脑电信号同步化的初步研究

研究α频率（8-13Hz）闪光刺激是否能引起人脑枕区同频率脑电信号的增加。采集15名正常志愿者在平静、光刺激状态下的脑电信号,利用脑地形图、小波分析和功率谱估计的方法对α频率光刺激前后的脑电信号进行处理,将归一化后的数据分为平静-激活组、男女对照组、两个不同电极位置组进行对比分析,对组间信号的差异进行了讨论,并对受试者精神状态的变化进行初步探讨。结果表明：周期性α频率光刺激能引起大脑枕区同频率脑电的显著增加。通过分析实验数据,初步得到了大脑在外部闪光刺激时脑电的变化规律,本实验结果对研究外部刺激对脑电的影响有一定的参考价值。     

α频率光刺激脑电信号同步化的初步研究

研究α频率(8～13Hz)闪光刺激是否能引起人脑枕区同频率脑电信号的增加.采集15名正常志愿者在平静、光刺激状态下的脑电信号,利用脑地形图、小波分析和功率谱估计的方法对α频率光刺激前后的脑电信号进行处理,将归一化后的数据分为平静-激活组、男女对照组、两个不同电极位置组进行对比分析,对组间信号的差异进行了讨论,并对受试者精神状态的变化进行初步探讨.结果表明:周期性α频率光刺激能引起大脑枕区同频率脑电的显著增加.通过分析实验数据,初步得到了大脑在外部闪光刺激时脑电的变化规律,本实验结果对研究外部刺激对脑电的影响有一定的参考价值.     

Cortical edema in moderate fluid percussion brain injury is attenuated by vagus nerve stimulation

Development of cerebral edema (intracellular and/or extracellular water accumulation) following traumatic brain injury contributes to mortality and morbidity that accompanies brain injury. Chronic intermittent vagus nerve stimulation (VNS) initiated at either 2 h or 24 h (VNS: 30 s train of 0.5 mA, 20 Hz, biphasic pulses every 30 min) following traumatic brain injury enhances recovery of motor and cognitive function in rats in the weeks following brain injury; however, the mechanisms of facilitated recovery are unknown. The present study examines the effects of VNS on development of acute cerebral edema following unilateral fluid percussion brain injury (FPI) in rats, concomitant with assessment of their behavioral recovery. Two hours following FPI, VNS was initiated. Behavioral testing, using both beam walk and locomotor placing tasks, was conducted at 1 and 2 days following FPI. Edema was measured 48 h post-FPI by the customary method of region-specific brain weights before and after complete dehydration. Results of this study replicated that VNS initiated at 2 h after FPI: 1) effectively facilitated the recovery of vestibulomotor function at 2 days after FPI assessed by beam walk performance (P<0.01); and 2) tended to improve locomotor placing performance at the same time point (P=0.18). Most interestingly, results of this study showed that development of edema within the cerebral cortex ipsilateral to FPI was significantly attenuated at 48 h in FPI rats receiving VNS compared with non-VNS FPI rats (P<0.04). Finally, a correlation analysis between beam walk performance and cerebral edema following FPI revealed a significant inverse correlation between behavior performance and cerebral edema. Together, these results suggest that VNS facilitation of motor recovery following experimental brain injury in rats is associated with VNS-mediated attenuation of cerebral edema.     

脑房室模型的建立与脑血流的定量分析

为了简化无创的脑血流的定量方法,我们应用计算机仿真技术和以脉冲函数作为房室模型的输入函数,计算了24例患者脑99mTc-ECD时间-放射性曲线的脑存积分数.结果表明二室模型的脑存积分数R2和三室模型的脑存积分数R3在α=0.01水平上显著相关,相关系数为0.9836; 用R2和 R3计算脑血流量分别为29.48±1.51 和29.10±1.48 ml/min/100g, 两者之间无显著性差异(P＞0.05,n=24).这表明我们所提出的简化后的二室模型能够较好地刻划99mTc-ECD在脑内的分布机制,用脉冲函数作为模型的输入函数比用左心室的时间放射性曲线更为合适.     

Evaluating the relationship of non-phase locked activities in the electroencephalogram during intermittent stimulation: a partial coherence-based approach

Partial coherence estimate between two signals removing the contribution of a periodic, deterministic one is proposed for measuring the coherence between two ongoing eletroencephalografic (EEG) activities collected at distinct cortical regions under sensory stimulation. The estimator expression was derived and shown to be independent of the stimulating signal. Simulations were used for obtaining the critical values for this coherence estimate. The technique was also evaluated throughout simulations and next applied to the EEG from 12 subjects under intermittent photic stimulation at 4 and 6 Hz. In both simulation and EEG data, major differences between partial and simple coherences occurred at the stimulation frequency and harmonics, except for those falling within the alpha band. These findings suggest that the technique is highly selective in removing the contribution of the periodic source. They also indicate high coherence values of the ongoing EEG within the alpha band.     

The efficacy of frequency-specific acupuncture stimulation on extracellular dopamine concentration in striatum—A rat model study

Acupuncture is a practice that has existed in Chinese society for thousands of years. Today, it is gaining greater acceptance and integration into medical practices of the western world. Its mechanism, however, remains elusive. Our study shows that only specific stimulation frequencies at specific acupoints will induce dopamine release in the corpus striatum, as demonstrated by in vivo microdialysis performed on Sprague–Dawley rats. In the first trial, electroacupuncture (EA) stimulation at 15 Hz and 15 mA was conducted at six different points on the upper limbs of the experimental rats. These points mimic acupoints along six different meridians in the human body. Only Point 2 (corresponding to Pericardium 7) induced a response. In the second trial, EA stimulation at varying frequencies of 3, 6, 9, 12, 15, 18, 21, 24, 27 and 30 Hz, and 15 mA were conducted through Point 2. Stimulation at 6 and 15 Hz induced an immediate response; 21 Hz induced a response only after the ceasing of stimulation. All other frequencies failed to induce a response. The data point to the importance of frequency-specific stimulation at specific acupoints for the release of neurotransmitters in the brain. We speculate that each meridian entails a stimulus of a specific frequency and intensity, which induces the release of its associated neurotransmitters or cytokines. This is a concept with far-reaching clinical implications for acupuncture therapy, including the treatment of dopamine-related disorders.     

Optimization of single electrode tactile codes

The effects of a frequency modulated electrocutaneous signal's (code's) characteristics on the interpretability of the signal were investigated using an electrocutaneous tracking approach. The characteristics investigated include the functional relationship (exponential and hybrid) between an informational signal and the stimulation frequency, the range of stimulation (2–50 Hz and 2–100 Hz), and the impact of pulse width compensation on a code's efficacy. The interpretability of six different single bipolar electrode codes was examined by 30 subjects using a balanced incomplete block experimental design. Codes with exponentially shaped transfer functions resulted in generally lower electrocutaneous tracking errors than codes utilizing hybridshaped transfer functions. Hybrid codes had a transfer function that was linear in the lower frequency range and exponential in the higher frequency range. Codes with a 2–100 Hz frequency range were interpreted better than codes with a 2–50 Hz frequency range. The use of pulse width compensation to maintain a more even level of stimulation intensity had a slightly negative effect on the subjects' abilities to cutaneously track the information signal.     

What are the stimulation parameters that affect the extent of twitch force potentiation in the adductor pollicis muscle?

Muscle force potentiation affects force output during electrical stimulation. Few studies have examined stimulation train parameters that influence potentiation such as pulse number, stimulation frequency, train duration, and force–time integral and peak force produced during the train. Pulse-matched trains (100 pulses) at 7.5, 15, 25, 30, 50, and 100 Hz, and trains of varying pulse number (50, 100, and 200 pulses) at 30 and 50 Hz were delivered to the ulnar nerve of 10 (5 male, 5 female; 23.4 ± 0.9 years), healthy individuals in random order. Single twitches of the adductor pollicis muscle were elicited before and after each train with a rest interval of at least 5 min between each train. No differences in potentiation occurred across the pulse-matched trains at frequencies of 15–50 Hz (38.9 ± 5.4–44.6 ± 5.5%). Twitch force potentiation following the highest (100 Hz) and lowest (7.5 Hz) frequency trains were not significantly different and were lower than the other 100 pulse-matched trains. As pulse number increased, potentiation increased for both the 30 and 50-Hz trains. There was a significant positive correlation between force potentiation and force–time integral produced by the stimulation train, r = 0.70. The results indicate that potentiation magnitude is dependent on the force–time integral produced during the test train and the number of pulses delivered, independent of stimulation frequency.     

Coupling Between Resting Cerebral Perfusion and EEG

While several studies have investigated interactions between the electroencephalography (EEG) and functional magnetic resonance imaging BOLD signal fluctuations, less is known about the associations between EEG oscillations and baseline brain haemodynamics, and few studies have examined the link between EEG power outside the alpha band and baseline perfusion. Here we compare whole-brain arterial spin labelling perfusion MRI and EEG in a group of healthy adults (n = 16, ten females, median age: 27 years, range 21–48) during an eyes closed rest condition. Correlations emerged between perfusion and global average EEG power in low (delta: 2–4 Hz and theta: 4–7 Hz), middle (alpha: 8–13 Hz), and high (beta: 13–30 Hz and gamma: 30–45 Hz) frequency bands in both cortical and sub-cortical regions. The correlations were predominately positive in middle and high-frequency bands, and negative in delta. In addition, central alpha frequency positively correlated with perfusion in a network of brain regions associated with the modulation of attention and preparedness for external input, and central theta frequency correlated negatively with a widespread network of cortical regions. These results indicate that the coupling between average EEG power/frequency and local cerebral blood flow varies in a frequency specific manner. Our results are consistent with longstanding concepts that decreasing EEG frequencies which in general map onto decreasing levels of activation.     

Frequency dependent corticofugal excitation of principal cells in the cat's dorsal lateral geniculate nucleus

Excitatory postsynaptic potentials (EPSPs) were evoked in principal cells of the cat's dorsal lateral geniculate nucleus by electrical stimulation of cortico-geniculate fibres. The EPSPs had a pronounced frequency sensitivity. They were barely detectable at stimulation frequencies below 3 Hz but increased dramatically in size at higher frequencies. At 30-50 Hz their amplitude typically exceeded that of EPSPs from optic tract fibres. A prominent EPSP potentiation was also obtained with pair pulse stimulation. The findings are discussed in relation to the hypothesis that the cortico-geniculate system serves as a variable gain regulator for the visual input to the cortex.     

Frequency dependent corticofugal excitation of principal cells in the cat's dorsal lateral geniculate nucleus

Summary Excitatory postsynaptic potentials (EPSPs) were evoked in principal cells of the cat's dorsal lateral geniculate nucleus by electrical stimulation of cortico-geniculate fibres. The EPSPs had a pronounced frequency sensitivity. They were barely detectable at stimulation frequencies below 3 Hz but increased dramatically in size at higher frequencies. At 30–50 Hz their amplitude typically exceeded that of EPSPs from optic tract fibres. A prominent EPSP potentiation was also obtained with pair pulse stimulation. The findings are discussed in relation to the hypothesis that the cortico-geniculate system serves as a variable gain regulator for the visual input to the cortex.