大鼠 C 类传入纤维诱发的脊髓背表面电位

实验共用大鼠66只,以激活 C 类纤维的强度刺激腓肠神经,在脊髓背表面除记录到 A 类纤维诱发的 N_1、N_2和 P_1波外,还见一长潜伏期正波。该波与 P_1波方向一致,波形类似,故称之为 P_2波。P_2波潜伏期为133.3±13.7ms, 时程为83.3±21.9ms,幅度为154.8±92.8μV.P_2波的刺激阈值(33.7±11.8T)与复合动作电位 C 波的阈值(33.1±11.8T)相同或略高,当刺激强度达87.1±15.4T 时,两者幅度同时达最大值。P_2波的潜伏期与 C 类传入抵达脊髓的时间(125.6±13.4ms)非常接近,缩短外周传导距离所致 P_2波潜伏期的缩短(39.8±5.7ms)与 C 类传入经过缩短段所需时间(38.8±5.7ms)基本一致。用直流电阻断 A 类传入仅保留 C波时,N_1、N_2、P_1波消失而 P_2波仍存在,加大阻断电流使 C 波消失时,P_2波随之消失。以上结果表明 P_2波是 C 类传入诱发的脊髓电位。脊髓横断后 P_2波并不消失,P_2波在脊髓背表面的纵向分布与 P_1波基本平行,注射印防己碱后 P_2波与 P_1波都有减小,说明 P_2波的性质与 P_1波类似,可能是 C 类传入主要经脊髓环路诱发的初级传入末梢去极化,或许可作为突触前抑制指标。     

稳态白噪声对豚鼠耳蜗电位影响的研究

本工作利用面神经管慢性埋植电极在清醒动物上对噪声暴露前后听神经动作电位(AP)和微音器电位(CM) 进行了研究,结果表明:当改变测试声强和频率时CM应起始点会发生移位(CM-shift); 123dBSPL稳态白噪声暴露1小时后.AP各参数(幅值、潜伏期和阈值)均发生明显变化.而CM各参数(幅值、CM-shift和检测阈)变化则基本未达显著性.说明AP对产损伤的敏感性要高于CM另外发现噪声暴露后AP的N_2峰的恢复比N_1峰快、CM在恢复过程中会出现幅值加大现象.     

短声特性对豚鼠圆窗记录的N_1N_2反应的影响

研究了不同刺激声强情况下短声特性(极性、波形及相应频谱)改变对豚鼠圆窗记录的N_1N_2反应的影响。发现:①在低声强时,若维持刺激声强不变而使短声波形改变对N_1无影响,但是对N_2有轻微的影响。而高声强时,若维持刺激声强不变而使短声波形改变将引起N_N_2反应较为显著的变化。②不仅是短声的疏相,而且其密相对N_1N_2的形成有贡献。③N_1N_2反应不仅与短声刺激强度有关,而且还与短声的其它参数(如波宽等)有关。并就各项结果进行了讨论。     

猫听觉脑干诱发电反应中P_(2a)和P_(2b)波的起源

在33例猫将普鲁卡因或海人酸微量注入耳蜗核(CN)和上橄榄复合体(SOC)内,观察ABR的相应改变,以分析P_(2a)和P_(2b)波的来源。猫P_(2a)波的出现率与电极导联有关,颅顶-颈后为90％,颅顶-乳突仅为18％。普普卡因注入CN后,同侧耳短声诱发的ABR仅保留P_1波,对侧耳的则无改变。海人酸注入CN后,P_1和P_(2a)存留,P_(2a)不减小反而增大。普鲁卡因注入双侧SOC,可使P_3、P_4和P_5消失。这些结果提示,P_(2a)波主要起源于CN区域内的第一级听觉传入神经元轴突并受第二级神经元负电位的影响,P_(2b)波主要起源于SOC以下的第二级听觉传入神经元,猫的P_(2a)和P_(2a)波与对侧脑干结构无关。     

不同时间频率光栅刺激引起的视觉诱发电位(VEP)方位效应的差异

以人视觉诱发电位(VEP)反应为指标,在不同的时间频率下测定了 VEP 对方波光栅刺激的反应幅度与光栅方位的关系。当光栅方位固定时,光栅闪烁的时间频率不同,VEP 反应的波形、潜伏期和反应频率差别很大,但其反应幅度均呈现方位选择性。当光栅的时间频率为9.1Hz时,光栅为垂直和水平方位时引起的 VEP 反应幅度比倾斜方位时都大,对任何光栅方位,VEP反应幅度与光栅对比度的对数呈线性关系;与此相反,当光栅时间频率为0.4Hz 时,光栅为倾斜方位时引起的 VEP 反应幅度比垂直和水平方位时更大。     

前部缺血性视神经病变患者图形视觉诱发电位与视功能改变的关系及其临床意义

目的:探究前部缺血性视神经病变(AION)患者图形视觉诱发电位(P-VEP)检查结果与预后间的关系。方法:选择2016年12月-2019年12月于我院就诊并确诊的AION患者作为研究对象,入院后接受综合治疗,治疗后评估患者的视功能,评价患者的治疗效果,采用相关性分析探究患者入院后P-VEP检查结果与经治疗后患者视功能改善值间的相关性。结果:研究组15'棋盘格和60'棋盘格P100波潜伏时均高于对照组,P100波振幅均低于对照组,差异均具有统计学意义(P0.05)。治疗后3个月AION患者最佳矫正视力和视野平均敏感度(MS)高于治疗前,视野平均缺失值(MD)低于治疗前,差异均具有统计学意义(P0.05)。AION患者治疗前后视力差值与15'棋盘格P100波振幅呈正相关,视野MD差值和视野MS差值与P-VEP四项反应值不具有相关性。结论:P-VEP检查结果 15'棋盘格P100波振幅与患者视力改善差值间存在显著的正相关性,可提示患者视功能恢复程度及预后。     

子一代表型数的估计式

设A_(11)A_(12)B_(11)B_(12)…N_(11)N_(12)和A_(21)A_(21)B_(21)B_(21)…N_(21)N_(22)分别是亲本P_1和P_2的基因型;a_(11),a_(12),a_(21)和a_(22)是控制同一性状的一组具有显隐关系的等位基因(a=A,…,N)。假定这n组等位基因互不连锁,且一组等位基因与另一组等位基因间没有相互作用,那么公式     

对清醒与麻醉鼠脑辅酶类物质的活体探测

以氮分子激光脉冲(40μJ Pulse 3HZ)为激发光通过石英光导纤维,导入大白鼠脑皮层;使脑内一些辅酶类物质(二核苷酸类和喋呤类)受激而发射出的荧光脉冲也由同一根光导纤维引出,以弱荧光检测技术对发射荧光脉冲进行检测.同时,还记录了激光诱发皮层电位,利用高效液相色谱法分析了六个脑区内的二核苷酸和喋呤物质的浓度.结果表现异戍巴比妥麻醉的动物与清醒动物相比激光——荧光脉冲波幅显著增高,但激光诱发皮层电位(N_(200)波和P_(300)波)的波幅则显著降低.在皮层、间脑和海马中黄素辅酶(FAD)的浓度显著增高,皮层、尾状核和脑干内的主物喋呤含量降低;脑干中喋呤的含量(?)显著降低.     

对清醒与麻醉鼠脑辅酶类物质的活体探测

以氮分子激光脉冲(40μJ Pulse 3HZ)为激发光通过石英光导纤维,导入大白鼠脑皮层;使脑内一些辅酶类物质(二核苷酸类和喋呤类)受激而发射出的荧光脉冲也由同一根光导纤维引出,以弱荧光检测技术对发射荧光脉冲进行检测.同时,还记录了激光诱发皮层电位,利用高效液相色谱法分析了六个脑区内的二核苷酸和喋呤物质的浓度.结果表现异戍巴比妥麻醉的动物与清醒动物相比激光——荧光脉冲波幅显著增高,但激光诱发皮层电位(N_(200)波和P_(300)波)的波幅则显著降低.在皮层、间脑和海马中黄素辅酶(FAD)的浓度显著增高,皮层、尾状核和脑干内的主物喋呤含量降低;脑干中喋呤的含量(?)显著降低.     

早产儿40Hz听觉相关电位的神经发育特性

临床实验研究发现:1.早产儿40Hz AERP Pa和Pb波潜伏期在三种强度(40,60和80dB-nHL)的短音(500Hz)刺激下明显长于足月新生儿(P<0.05,P<0.01,P<0.001),Pa-Pb波间期未见显著性变化(P>0.05);2.早产儿40Hz AERP Pa和Pb波潜伏期与500Hz短音强度高度相关(r≥0.98),Pb波潜伏期-刺激强度函数斜率K值明显有别于Pa波K值(P<0.01);3.早产儿40Hz AERP Pa和Pb波潜伏期与孕龄高度相关(r>0.7),Pb波潜伏期-孕龄函数斜率K值亦明显区别于Pa波K值(P<0.05)。     

Reliability and upper normal variability limits of pattern reversal visual evoked potential parameters.

Twenty healthy volunteers aged 21-48 years (10 males, 10 females) were submitted to pattern reversal visual evoked potentials with 15' and 30' checks. The recordings were repeated after 7 days to assess reliability and upper normal variability limits of the following parameters: latencies of N70, P100, N140 and peak-to peak amplitudes of N70-P100, P100-N140. Reliability was tested with intraclass correlation coefficient, which was excellent or good for all parameters. Test-retest variability limits were computed with = 0.01 for absolute latency differences and relative amplitude differences.     

Changes in visual evoked potentials observed in humans involved in cleanup work after the Chernobyl’ catastrophe

We studied the parameters of visual evoked potentials (VEP) recorded in humans involved in the cleanup work after the Chernobyl’ catastrophe and in persons of the control group. The VEP evoked by presentation of a reversing chessboard pattern were significantly modified in the group of cleanup workers: in many subjects their shape was drastically changed, the mean latent periods for P100 and N145 waves increased, and their amplitudes significantly dropped. The amplitude of the P200 component somewhat increased in the group of cleanup workers. Possible reasons for the observed changes in the evoked electrical activity and the mechanisms underlying the changes in the visual analyzer of the persons subjected to long-term irradiation are discussed.     

Contrast transfer function of the visual system]

Visually evoked potentials were used to determine the spatial contrast response function of the visual system and the visual acuity of the pigeon. The spatial contrast response describes the relationship between the contrast in a pattern of vertical stripes, whose luminance is a function of position, and the amplitude of the visually evoked response at various spatial frequencies for a given temporal frequency (pattern reversal frequency); it indicates how particular spatial frequencies are attenuated in the visual system. The visually evoked responses were recorded using monopolar stainless steel electrodes inserted into the stratum griseum superficiale of the optic tectum; the depth of penetration was determined on the basis of a stereotactic atlas. The stimulus patterns were generated on a video monitor placed 75 cm in front of the animal's eye perpendicular to the optic axis. The spatial contrast response function measured at 10% contrast and 0.5 Hz reversal frequency shows a peak at a spatial frequency of 0.5 c/deg, corresponding to 1 degree of visual angle, and decreases progressively at higher spatial frequencies. The high-frequency limit (cut-off frequency) for resolution of sinusoidal gratings, estimated from the contrast response function, is 15.5 c/deg, corresponding to a visual acuity of 1.9 min of arc.     

Directed attention influence on the human brain potentials under conditions of probability visual stimulation

Saccadic latency and averaged EEG-potentials connected with switching on of the set and cue visual stimuli were examined in 12 right-handed healthy subjects in M. Posner's "cost-benefit" experimental paradigm. It was shown that attention was reflected in parameters of positive potential P100 evoked by switching on of set and cue stimuli and P300 and slow positive wave PMP1 evoked by switching on of the set stimulus in the relevant conditions. The spatiotemporal pattern of P100 probably reflects the involvement of the frontoparietal network of spacial attention in the perception of a relevant stimulus. Prevalence of the P300 and PMP1 potentials in the right parietal cortex suggests that these potentials reflect processes of space attention and visual fixation. Late positive potentials in a 600-900-ms interval after switching on of the set stimulus were found. Their amplitude was higher in backward averaging and they were predominantly localized in the left frontal cortex. These findings suggest that the late potentials reflect the anticipation and motor attention processes.     

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.     

Reflection of the intensity of peripheral stimulation in the amplitude-time parameters of somatosensory and kinesthetic evoked potentials of the projection cortex in rhesus macaques

Experiments were made on 7 adult male monkeys under nembutal anaesthesia (20-25 mg/kg, intravenously). The evoked potentials to electrical stimulation (0.5-50 mA) of the skin and kinestetic (5.10(3)-6.10(5)degrees/s2) stimulation of the proximal part of the forearm were recorded in the contralateral primary somatosensory cortex. The data obtained indicated direct relationship between the magnitude of angular acceleration and amplitude-temporary parameters of the kinestetic potentials. The threshold for their detections was equal approximately to 5.10(3) degrees/s. Maximum amplitude and the shortest latency were observed at accelerations 100 times higher than threshold ones. These data are compared with parameters of the evoked potentials to the electrical stimulation of the skin.     

Serial visual evoked potential recordings in Alzheimer's disease.

Primary presenile dementia slows the major positive component of the visual evoked potential to flash stimulation but does not affect the visual evoked potential to patterned stimulation. The progressive effect of Alzheimer''s disease was followed in a 58 year old woman over three and a half years from the development of the earliest symptoms to complete mental incapacity. The pattern reversal visual evoked potential remained normal, but the flash visual evoked potential gradually slowed from 129 ms in 1981 to 153 ms in 1984. The severity of the abnormality of the flash visual evoked potential thus reflected the severity of the dementia. Electroencephalography, computed tomography, and psychometric tests indicated generalised cortical disease, but the results were not specific to dementia. The combination of a slowed flash and normal pattern visual evoked potential seems to be specific to Alzheimer''s disease and supports the use of flash and pattern visual evoked potentials in routine diagnostic testing for this condition.     

Cortical representation of nonclassical parts of the visual system

Cortical evoked potentials and extracellular evoked neuronal activity have been investigated in unanesthetized d-curarine immobilized rats during stimulation of the superior colliculi. The focus of responses was found in the lateral part of the visual neocortex (area 18a according to Krieg [5]). The evoked potential includes a negative and subsequent positive waves, its latency being equal to 7.9 +/- 2.8 msec. With deepening the electrode the amplitude of the response decreases, although its polarity remains unchanged. The neuronal activity is of phasic character. During simultaneous record of the evoked potentials and neuronal activity, temporal correlation between impulse activity and the ascending part of the main negative wave of the EP is observed. The data obtained indicate imcomplete overlapping of the retino-geniculo-cortical and retino-tecto-thalamo-cortical channels in the visual system of rats.     

Changes in characteristics of sensory evoked potentials in dynamics of monotonous activity

Visual and auditory evoked potentials were recorded in 19 volunteers during their monotonous activity. Three groups of subjects different in performance quality were set aside. Characteristics of evoked potential components were subjected to analysis of variance. The latency of P1 component of visual and auditory evoked potentials recorded in respective projection cortical areas significantly increased over the course of the long-term monotonous activity. These changes were associated with performance deterioration. The observed changes in performance quality and brain functional state were determined by individual features of subjects.     

Pattern visual evoked potentials in the early diagnosis of optic neuropathy in the course of Graves' ophthalmopathy

THE AIM OF THE STUDY: To investigate by means of pattern visual evoked potentials (PVEPs) early neuropathic changes in Graves' ophthalmopathy (GO) patients without any clinical symptoms of optic neuropathy in order to evaluate the prevalence of subclinical optic neuropathy in GO patients and to elucidate whether there is a relationship between PVEP (P100 and N75 latency), intraocular pressure (IOP) and exophthalmometry. MATERIAL AND METHODS: Two groups of patients were examined: 15 patients with GO without clinical signs of dysthyroid optic neuropathy (DON) and 12 healthy controls. The correlations between the N75 and P100 latencies, IOP and Hertel exophthalmometry were investigated. RESULTS: The mean PVEP N75 and P100 latencies were significantly delayed in the GO uncomplicated with DON in comparison with controls (LP100- 106.2 +/- 4.4 ms vs. 102.4 +/- 2.7 ms, p < 0.01 and LN75- 79.0 +/- 3.7 ms vs. 73.9 +/- 2.8 ms, p < 0.001). In GO patients we documented a positive correlation between the LN75 latency and exophthalmometric readings (R = 0.51; p < 0.01). The value of LP100 and LN75 was above the normal limit in 5/30 eyes (17%) and in 3/30 eyes (10%) respectively. CONCLUSIONS: The assessment of PVEPs (especially the P100 latency) in GO patients without clinical signs of DON is a useful tool for the early diagnosis of optic nerve involvement.