K—L变换在视诱发电位特征分析中的应用

VEP(Visual Evoked Potentials)是在大脑视皮层记录到的一组诱发电位.它的形态变化对于视路病变,视神经病变等视系统疾患的临床诊断及发病机理的探讨都有重要价     

神经生长因子对大鼠视觉诱发电位的影响

目的和方法：本研究主要通过电生理方法,测定经CS2所致视神经损害的大鼠在治疗前后视觉诱发电位的变化,以证实神经生长因子对受损神经的治疗效果。结果：大鼠视神经损伤模型经神经生长因子治疗20d后,模式反转诱发电位和闪光诱发电位的潜伏期与对照组相比均有明显的缩短,并有量－效关系。结论：神经生长因子能明显改善视神经传导功能,提示神经生长因子对视神经损伤有一定的治疗作用。     

用脑光学成像精确测定猫初级视皮层视野拓扑投射关系

利用基于脑内源信号的光学成像和二维互相关分析的方法,对猫初级视皮层17区的视野拓扑离心度(即视网膜-皮层拓扑关系)进行了精确测量。当采用在同一屏幕内处于上下视野的、方位互相垂直的两个相邻光栅刺激时,皮层中一部分区域的绝大部分细胞因同时兴奋而导致方位功能图模糊不清。将这种方位功能图和用单一方位(水平或垂直)全屏光栅刺激所得到的功能图进行比较,通过计算每一像素的互相关系数,从而获得皮层的精确视野拓扑离心度。同时用电生理的方法测量了同一视皮层内的单细胞的感受野位置,证明这种方法得到的视野离心度和光学记录方法得到的相同。因此,本研究为大面积地确定视皮层细胞感受野在视野中的位置提供了一种快速和较准确的方法。     

大鼠皮层听-视多感觉神经元和听-视信息整合

应用常规电生理技术,研究SD大鼠皮层听-视多感觉神经元的分布和听-视信息整合.共记录到130个听-视双模态神经元,其中65个A-V型神经元,28个v-A型神经元和37个a-V型神经元.这些双模态神经元主要分布于听区的背侧,听皮层和视皮层的交界处,具有明显的区域性,呈条带状分布,v-A型神经元较多地位于近听皮层一侧,a-V型神经元则主要位于近视皮层一侧,A-V型神经元位于两者之间.在条带中,双模态神经元分布不均一,有片状分布趋势.双模态神经元的听-视信息整合效应分为增强型、抑制型和调制型.整合效应与声-光组合刺激的时间间隔有关,其中75%的神经元获得最大整合效应的时间间隔在30～50ms之间.研究结果提示,大鼠皮层存在听-视多感觉神经元分布区,这些神经元遵循存在于其他动物相关脑区多感觉信息整合规律,参与听-视感觉信息整合.     

正常成年猫多导程视觉诱发电位研究

用平面均匀闪光和棋盘格图形翻转刺激,研究了１７只正常猫的多导程视觉诱发电位（ＶＥＰｓ）,主要结果为：１．图形刺激引起的Ｐ－ＶＥＰ波形为两个正相成份（Ｐ１和Ｐ２）夹着一个负相成份（Ｎ１）组成“Ｗ”型的波复合;而平面均匀闪光引起的Ｆ－ＶＥＰ则为两个负相成分（Ｎ１和Ｎ１）成分夹着一个正相成分（Ｐ１）构成“Ｍ”型的波复合。这两种ＶＥＰ均表现出明显的双眼总和现象,而且Ｐ－ＶＥＰ的总和率大于Ｆ－ＶＥＰ的。２．     

阿托品对家鸽顶盖脑片Iia-f亚层诱发电位的影响

在２８例家鸽顶盖脑片上，以微电极记录电刺激顶盖Ⅰ层引起的Ⅱａ－ｆ亚层诱发电位，并观察乙酰胆碱受体拮抗剂阿托品和筒箭毒对诱发电位的影响。结果显示，该诱发电位包含两个波形成分，频率跟随实验提示属于突触后反应，以含２０μｍｏｌ／Ｌ阿托品的人工脑脊液（ＡＣＳＦ）灌流脑片１０ｍｉｎ后，诱发电位出现衰减，５０ｍｉｎ后波形成分完全消失，换含２０μｍｏｌ／Ｌ筒箭毒的ＡＣＳＦ灌流则对诱发电位没有影响。以上结果提示，     

不同年龄组立体视及图形诱发电位的对比研究

由微机产生动态随机点立体图(DRDS)和黑白棋盘格图形刺激 ,记录了30名立体视觉正常的成人、30名学龄儿童和30名学龄前儿童的动态立体视诱发电位 (DDEP)和双眼棋盘格图形刺激的诱发电位(PVEP)。实验结果表明 ,三组动态立体视诱发电位的N波潜伏时有显著差异 ,随着年龄的增长 ,N波潜伏时缩短 ;而棋盘格刺激的视觉诱发电位的P100波的潜伏时无显著性差异 ,但波幅有显著差异 ,学龄儿童的波幅最高 ,成人的波幅最低。由DEP在各个年龄组的演变规律与棋盘格图形VEP的演变规律的不一致揭示了视觉系统中立体视发育和类似于棋盘格刺激的较为初级的视功能发育是不同步的 ,它们具有不同的发育规律 ;12岁以下儿童立体视仍具有可塑性。     

正常儿童多导视觉诱发电位的非对称性分布

对４９名正常儿童进行了多导视觉诱发电位的观察。结果表明：（１）双眼及单眼ＶＥＰｓ波形在头皮中线两侧分布是非对称性,右偏者较左偏者多,这种非对称性可能与脑组织两侧结构和功能的不对称有关,从而影响到ＶＥＰｓ发生源的位置以及偶极子的方向及强度等。（２）吉利手者右半视野刺激的ＶＥＰｓ振幅,（ＡｎｌＰ１）大于左半视野刺激的ＶＥＰｓ振幅,两半球枕叶皮层神经解剖学上的非对称性为我们的电生理结果提供了一定的形态结构基础。（３）半视野刺激显示“矛盾定侧”现象。     

痛觉诱发电位的研究进展

痛觉诱发电位的研究在过去的几十年内取得了重要进展 ,出现了许多用于被试的诱发明确疼痛感的刺激技术 ,并与诱发电位方法学联合应用 ,已经成为脑映像学研究中重要的组成部分。本文从刺激技术、痛觉诱发电位成分分析和偶极子源分析等方面出发 ,讨论了痛觉诱发电位的研究进展     

视觉诱发电位(VEP)方位效应与刺激位置的关系

以人视觉诱发电位(VEP)反应为指标,在视野的不同位置测定了VEP对四个方位的闪烁方波光栅刺激(时间频率2.9Hz,空间频率1.4c/deg,对比度0.94)的反应幅度。在距中央凹20°视角同心圆的八个刺激位置上,VEP反应幅度对与向心线垂直方位的光栅刺激(同心圆的切线方向),有统计意义上的优势。这一规律在垂直、水平向心线上尤为明显。从总体上未发现VEP反应幅度与刺激光栅方位有着明显的关系。这说明在人视野周边区,VEP反应幅度与光栅方位和向心线的夹角(偏向角)相关,而与光栅的绝对方位无关。在相同的刺激条件下,中央区的VEP反应幅度与刺激光栅方位之间也未发现明显关系。     

视觉诱发电位波形的自动判别分析及其临床应用

计算诱发电位波形第一至第六次谐波的幅度和相位,把这12个参数作为判别分析的自变量.用32只正常眼、31只弱视眼和30只球后视神经炎患眼的诱发电位波形数据建立判别分析系统,再用另外32只正常眼、35只弱视眼和30只球后视神经炎患眼的诱发电位波形数据检验该判别分析系统的判别效果.     

Modifications of Visual Evoked Potentials in Patients with Glaucoma

We compared the visual evoked EEG potentials (VEP) elicited by presentation of a reversal chess pattern in patients with glaucoma and in the control group. Amplitudes, peak latencies of the main VEP components (N75, P100, and N145), interpeak intervals, and interpeak magnitudes were measured, and a spectral analysis of the averaged VEP was performed. In patients suffering from glaucoma, the latencies of the N75 and P100 components were greater, while the interpeak intervals P100-N145 and N75-N145 were shorter, than those in the control group. Glaucoma-related changes in the VEP spectral characteristics, in particular a drop in the spectral power of oscillations corresponding to the alpha rhythm, were observed.     

Dependence of the Parameters of Visual Evoked Potentials on the Parameters of a Complex Visual Stimulus (Tests on Humans)

We recorded visual evoked potentials, VEP, elicited by presentation of a reversal chess pattern; 35 healthy persons were examined. A recording electrode was in point Oz, according to the 10-20 system; dimensions of the chess pattern square fields and their contrast varied from 1.8 to 120 and from 2 to 100%, respectively. Peak latencies, PL, of the N75 component depended on the contrast of stimulus elements in a U-like manner with the minimum within a 20-25% range. The PL of the P100 component monotonically increased with a decrease in the contrast, while the dependence of the PL of N145 was complex: a trend toward a decrease with a decrease in contrast to 30%, a local maximum in about 25%, a decrease and stabilization within a 15-4% range, and a sharp increase at the minimum contrast. The amplitude of N75 decreased with decrease in contrast down to 20-25% and then stabilized; the amplitude of P100 decreased in an S-like mode, with a plateau within 25-4%. The dependence of the N145 amplitude was complex, with a plateau-like maximum at 30-15% contrast. The amplitudes of the negative VEP components, N75 and N145, increased with an increase in the square dimensions to 7.5 and then decreased. Changes in the P100 amplitude included two phases, with a local minimum within an angular dimension range of 30-15^O. The PL of all analyzed components in general increased with a decrease in the angular dimension of the pattern components. The above data are discussed considering concepts on the genesis of different VEP components and on the existence of specialized channels in the visual system, which are responsible for detection of different parameters of a visual object. The complex dynamics of the PL of the analyzed VEP components and of the P100 amplitude related to variation of the contrast and angular dimensions of the elements of a complex stimulus are considered to be determined by a module principle of the organization of the elements constituting different levels of the visual system and by transformations of the receptive fields of these elements on the level of cortical modules, which are related to changes in the stimulus parameters.     

Visual Evoked Potentials and Disorders of Visual Function in Children Suffering from Cerebral Palsy

Using recording of visual evoked potentials (VEP), we examined 126 children (from 1 to 14 years old) suffering from spastic forms of cerebral palsy. In the overwhelming majority of cases (84.1%), we found in these patients significant modifications of the VEP related to dysfunctions of the visual analyzer system at different levels of the latter. We analyzed correlation of clinical manifestations of the disease with deviations of the VEP characteristics from the age norm. We conclude that an EEG examination, including VEP recording, allows one to obtain objective estimates of disorders of the visual function in the studied population of patients.     

Effect of Sahaja Yoga Meditation on Auditory Evoked Potentials (AEP) and Visual Contrast Sensitivity (VCS) in Epileptics

The effect of Sahaja yoga meditation on 32 patients with primary idiopathic epilepsy on regular and maintained antiepileptic medication was studied. The patients were randomly divided into 3 groups: group I practiced Sahaja Yoga meditation twice daily for 6 months under proper guidance; group II practiced postural exercises mimicking the meditation for the same duration; and group III was the control group. Visual Contrast Sensitivity (VCS), Auditory Evoked Potentials (AEP), Brainstem Auditory Evoked Potentials (BAEP), and Mid Latency Responses (MLR) were recorded initially (0 month) and at 3 and 6 months for each group. There was a significant improvement in VCS following meditation practice in group I participants. Na, the first prominent negative peak of MLR and Pa, the positive peak following Na did not register changes in latency. The Na-Pa amplitude of MLR also showed a significant increase. There were no significant changes in the absolute and interpeak latencies of BAEP. The reduced level of stress following meditation practice may make patients more responsive to specific stimuli. Sahaja Yoga meditation appears to bring about changes in some of the electrophysiological responses studied in epileptic patients.     

稳态视觉诱发电位神经网络间的相互作用

稳态视觉诱发电位(steady-state visual evoked potential,SSVEP)不同于瞬态视觉诱发电位,有其独特的产生机理。当用两种不同频率的闪光同时刺激时,每种频率闪光诱发的SSVEP之间是否会相互影响?它们与对应单一频率闪光刺激时产生的SSVEP的关系怎样?作者用!波段频率8.3Hz与"波段频率20Hz的闪光分别及同时刺激10个被试的双眼,发现在同时刺激时,每种频率闪光的SSVEP比对应单频刺激时的SSVEP略小,但位置分布无明显变化。这说明不同频率SSVEP的产生网络是彼此独立的,在被同时激活时,每个网络产生的信号并不相互影响。     

The developmental effects of extremely low frequency electric fields on visual and somatosensory evoked potentials in adult rats

Abstract

The purpose of our study was to investigate the developmental effects of extremely low frequency electric fields (ELF-EFs) on visual evoked potentials (VEPs) and somatosensory-evoked potentials (SEPs) and to examine the relationship between lipid peroxidation and changes of these potentials. In this context, thiobarbituric acid reactive substances (TBARS) levels were determined as an indicator of lipid peroxidation. Wistar albino female rats were divided into four groups; Control (C), gestational (prenatal) exposure (Pr), gestational+ postnatal exposure (PP) and postnatal exposure (Po) groups. Pregnant rats of Pr and PP groups were exposed to 50?Hz electric field (EF) (12?kV/m; 1?h/day), while those of C and Po groups were placed in an inactive system during pregnancy. Following parturition, rats of PP and Po groups were exposed to ELF-EFs whereas rats of C and Pr groups were kept under the same experimental conditions without being exposed to any EF during 68 days. On postnatal day 90, rats were prepared for VEP and SEP recordings. The latencies of VEP components in all experimental groups were significantly prolonged versus C group. For SEPs, all components of PP group, P2, N2 components of Pr group and P1, P2, N2 components of Po group were delayed versus C group. As brain TBARS levels were significantly increased in Pr and Po groups, retina TBARS levels were significantly elevated in all experimental groups versus C group. In conclusion, alterations seen in evoked potentials, at least partly, could be explained by lipid peroxidation in the retina and brain.     

Evoked Potentials of the Somatic Cortex and EMG Reactions of the Shoulder Muscles Elicited by Passive Extension of the Elbow Joint in Unanesthetized Cats

We recorded electromyographic (EMG) reactions from the flexors of the elbow joint and evoked potentials (EP) from the somatic cortex (fields 3, 4, and 6) of unanesthetized cats. These reactions were elicited by perturbation of an external extensor loading applied to the arm and evoking passive extension of the elbow joint. Perturbation of the loading was performed in two modes: (i) with different fixed force moments within a 0.04–0.2 N·m range, but with a constant rate of change in this moment (3.2 N·m·sec^–1), and (ii) with a constant force moment magnitude (0.2 N·m), but with different rates of change in this moment (from 0.1 to 6.4 N·m·sec^–1). When the elbow joint was passively extended, an EMG response was generated in the m. biceps brachii. The amplitude of this response correlated with the amplitude of perturbation of the external loading, and the time course of the response was rather close to that of the evoked passive moment. It was possible to differentiate several (up to seven) successive components in EP recorded from the three above-mentioned cortical fields; among them, the component N(50–60) was the most stable and clearly manifested. Its amplitude did not depend on the level of external loading and decreased with a decrease in the rate of loading perturbation. The time course of the N(50–60) changed insignificantly with variation of temporal parameters of the stimulus and of the evoked movement. We conclude that the spinal level and the cortical level responsible for formation of the stretch reflex differ significantly from each other in their functional roles. Reactions of the spinal level (which could be characterized by changes in EMG) are to a greater extent related to a change in the position of the limb link, while reactions of the cortical level (EP) are determined by the arrival of information about changes in the forces applied to the joint. Neurons of the somatic cortex, which are excited in the course of the stretch reflex, cannot be considered the main source responsible for generation of the M2 component of the myographic response. It is supposed that the cortical level predetermines the formation of non-reflex motor commands related to motor reflexes closed in the somatic brain cortex.     

Long-Term Changes in Spinal Cord Evoked Potentials After Compression Spinal Cord Injury in the Rat

SUMMARY 1. After traumatic spinal cord injury (SCI), histological and neurological consequences are developing for several days and even weeks. However, little is known about the dynamics of changes in spinal axonal conductivity. The aim of this study was to record and compare repeated spinal cord evoked potentials (SCEP) after SCI in the rat during a 4 weeks’ interval. These recordings were used: (i) for studying the dynamics of functional changes in spinal axons after SCI, and (ii) to define the value of SCEP as an independent outcome parameter in SCI studies.2. We have used two pairs of chronically implanted epidural electrodes for stimulation/recording. The electrodes were placed below and above the site of injury, respectively. Animals with implanted electrodes underwent spinal cord compression injury induced by epidural balloon inflation at Th8–Th9 level. There were five experimental groups of animals, including one control group (sham-operated, no injury), and four injury groups (different degrees of SCI).3. After SCI, SCEP waveform was either significantly reduced or completely lost. Partial recovery of SCEPs was observed in all groups. The onset and extent of recovery clearly correlated with the severity of injury.There was good correlation between quantitated SCEP variables and the volumes of the compressing balloon. However, sensitivity of electropohysiological parameters was inferior compared to neurological and morphometric outcomes.4. Our study shows for the first time, that the dynamics of axonal recovery depends on the degree of injury. After mild injury, recovery of signal is rapid. However, after severe injury, axonal conductivity can re-appear after as long as 2 weeks postinjury.In conclusion, SCEPs can be used as an independent parameter of outcome after SCI, but in general, the sensitivity of electrophysiological data were worse than standard morphological and neurological evaluations.