The cumulative heat strain index--a novel approach to assess the physiological strain induced by exercise-heat stress

We investigated the effect of increases in muscle afferent information from the shoulder girdle elevators on saccadic reaction time. Saccadic reaction time was measured under conditions of isometric voluntary contraction of the shoulder girdle elevators and vibratory stimulation of the trapezius. Saccadic reaction time was defined as the latency until the beginning of eye movement toward the lateral target, which was moved at random time-intervals in jumps of 20°amplitude. Eye movement was measured using the electro-oculogram technique. Muscle contraction force was set in 10% increments from 0% to 30% of maximal voluntary contraction (MVC), and vibration frequency was maintained at 100 Hz. Under voluntary contraction, the saccadic reaction time gradually shortened up to 30% MVC. Under vibration stimulation at 0% MVC, the reaction time shortened to the same degree as that under voluntary contraction at 30% MVC. Under conditions of combined vibratory stimulation and voluntary contraction, the reaction time was essentially identical to these values; namely, no additive effect in shortening of the reaction time was recognized. The results demonstrated that saccadic reaction times were remarkably shortened by increases in muscle afferent information from the neck extensors. We have discussed reasons for the lack of an additive effect and factors limiting shortening of reaction times. Electronic Publication     

眼挫伤后视力损害患者视觉诱发电位分析

目的:探讨视觉诱发电位(VEP)在评价挫伤后视力损害中的价值。方法:对74例挫伤性视力损害患者进行图形翻转刺激VEP测定,并与自体健侧眼和正常对照组进行比较。结果:74例患者中,单眼挫伤57例,双眼挫伤17例,共91眼受伤,受伤眼均有不同程度视力损害。VEP检查结果:91 眼中波形不典型者5眼(6％);P100波幅下降异常者54眼(59％);P100潜伏期延长者23眼(25％)。其中单纯潜伏期延长12眼(13％);单纯波幅下降异常43眼(47％);潜伏期延长伴波幅下降者11眼 (12％),总异常66眼,异常率为73％。所有挫伤后视力损害者,与自体健侧服和正常对照组比较,P100 潜伏期延长和波幅降低,差异均有显著意义(P<0．01)。结论:VEP为挫伤性视力损害的视功能评价、临床早期诊断、预后评估以及伤残鉴定提供了重要的客观依据。     

急性甲醇中毒患者的VEP分析

目的探讨急性甲醇中毒患者的视觉诱发电位（VEP）波形的异常变化及其与血甲醇浓度的相关性。方法对26例（52眼）甲醇中毒患者进行VEP检查及血甲醇浓度的测定。结果病程第一阶段共观察26人（52眼）,其中未引出VEP波形的有29只眼,波幅减低的有20只眼,波形P100潜伏期延长的有7只眼;病程第二阶段共观察17人（34眼）,其中未引出VEP波形的有10只眼,波幅减低的有22只眼,波形P100潜伏期延长的有11只眼;病程第三阶段共观察9人（18眼）,其中未引出VEP波形的有7只眼,波幅减低的有8只眼,波形P100潜伏期延长的有4只眼。未见血甲醇浓度与双眼P100潜伏期均值之间有明显相关性（P〉0.05）。结论VEP检查可以对甲醇中毒患者视神经功能损害提供可靠的诊断依据。急性甲醇中毒引起的视神经损害相对于异常甲醇浓度的降低以及其他临床症状消失具有滞后性与持续性。     

Visual evoked potential & brainstem auditory evoked potentials in acute attack & after the attack of migraine

PURPOSE: To study the effect on visual evoked potential (VEP) and brainstem auditory evoked potential (BAEP) at time of acute attack and after 7 days of the attack of migraine. MATERIAL AND METHODS: We studied BAEP and pattern reversal VEP in 25 patients during acute attack and after 7 days of the attack. The diagnosis of migraine was established according to criteria given by international headache society (IHS). Peak and interpeak latencies (IPL's) of BAEP and P100 latency of VEP were the main criteria to judge abnormalities. RESULTS: There were prolonged peak and interpeak latencies in BAEP and prolonged peak latency (P100) in VEP at the time of acute attack of migraine. The data of these abnormal recording were highly significant. After 7 days when the attack was over, we recorded the BAEP and VEP again. The observation obtained at this time was comparable to normal values. CONCLUSIONS: From the observation of this study we can safely conclude that in acute attacks of migraine there may be some pathological changes in different areas of brain and brainstem, producing changes in evoked potential which are statistically highly significant. However, these changes are reversible, as the values of BAEP & VEP on 7th day after the attack were comparable to those observed in normal healthy control.     

Susceptibility of the cat's visual system to hypoxia,hypotonia and circulatory arrest

Simultaneous recordings of sum potentials were made in the retina, the lateral geniculate nucleus (LGN), the superior colliculi (SC), and the visual cortex (VC) of cats. Light stimuli and electrical stimuli were alternatingly applied.A superposition of the effects of hypoxia/anoxia with an initial hyperexcitability in the central visual pathways due to disinhibition caused by the early failure of retinal ganglion cell maintained activity was avoided by photocoagulation of both retinae prior to the experiments.During hypoxia/anoxia induced by nitrogen respiration, the b-wave of the electroretinogram (ERG) displayed the earliest susceptibility, followed by the postsynaptic components of the VC, SC and LGN sum potentials, the OT-response to electrical stimuli, and the less susceptible receptor component of the ERG. The light-induced cortical visually evoked potential (VEP) disappeared together with the electrically elicited postsynaptic part of the VC response, while the ERG b-wave was still present. The same sequence of failures occured with a shorter latency after circulatory arrest elicited by air injection into the right atrium. During hypotonia produced by blood volume reduction, the b-wave began to decrease first at a mean arterial blood pressure of 60 mm Hg. The cortical VEP declined with the b-wave, while the responses to electrical stimulation remained unchanged until the mean arterial blood pressure values fell short of 40 mm Hg.     

Brain mapping of bilateral visual interactions in children

Interhemispheric interactions were studied with functional brain mapping of visual processing. Children performed a reaction time task with uni- and bilateral targets and nontargets. The visual evoked potential (VEP) was segmented into P1a, P1b, and N1 microstates using map rather than channel features. Map latencies, amplitudes and sources were tested for bilateral interactions. Bilateral targets yielded shorter VEP map latencies but later response onsets than unilateral ones. Source analyses of the unilateral VEPs indicated a transition from contra- (P1a) to ipsilateral (P1b) visual cortex activation (interhemispheric transfer). Bilateral VEPs were smaller than the summed unilateral VEPs in all microstates. indicating that interhemispheric interactions both precede and follow interhemispheric transfer. Brain mapping of uni- and bilateral VEPs in children thus revealed several distinct forms of interhemispheric interactions in the same, early time range.     

Effects of neck flexion on discriminative and cognitive processing in anticipatory postural control during bilateral arm movement

We investigated the effect of neck flexion on discriminative and cognitive processing in postural control during bilateral arm movement while standing, using event-related potential (ERP) and electromyogram. Fourteen healthy subjects flexed their arms to the target stimuli with a 20% probability in neck resting and flexion positions. Amplitude and latency of N2 and P3, anterior deltoid (AD) reaction time, onset time of postural muscles with respect to AD activation, and peak amplitude and latency of all muscles were measured. With neck flexion, N2 and P3 amplitudes increased, N2 and P3 latencies and AD reaction time shortened, and onset times of all postural muscles became earlier. No significant differences in peak amplitude and latency of each muscle were found between neck positions. Significant positive correlations were found in changes with neck flexion between P3 latency and AD reaction time, and between N2 latency and onset time of erector spinae. These suggest that with neck flexion, attention allocation to discriminative and cognitive processing increased, and the processing speed increased with shortening of reaction time in focal muscles. In addition, the onset time of postural muscles became earlier without changing the activation pattern, which was associated with the hastened discriminative processing.     

阿尔茨海默病与脑血管病痴呆患者的诱发电位比较研究

目的：观察阿尔茨海默病痴呆（AD）和脑血管病痴呆（VD）视觉及听觉诱发电位的特点。方法：收集25例AD组、24例VD及22名正常老年人（NC），完成听觉诱发电位（AEP）和视觉诱发电位（VEP）检查，并进行简易智力状态检查（MMSE）评分比较。结果：与NC组相比，AD组AEP的N1、P2，VEP的P1潜伏期延迟，AEP的P2、P2，VEP的P2、P3波幅降低；VD组VEP的P2潜伏期延迟，P2和P3波幅降低。AD组和VD组相比，AD组AEP的N1、P2潜伏期延迟于VD组。AD组VEP的P2波的潜伏期，VD组AEP的P3波幅及VEP的N1潜伏期改变与其MMSE评分有关联。结论：AD组和VD组的诱发电位有类似变化，两组的VEP和AEP变化与MMSE相关。     

Combined effects of alcohol and caffeine on the late components of the event-related potential and on reaction time

The effects of .7 ml/kg alcohol and 200 mg caffeine on the P200, N200, P300 and N500 difference wave components of the event-related potential and on reaction time (RT) were examined in 16 females who performed both simple and choice RT tasks. Alcohol slowed the decision time (DT) component of reaction time, lengthened the latency of the P200 and P300 components, reduced N200 amplitude, increased P300 amplitude at parietal sites, and modified the effect of sagittal site on N500 difference wave peak amplitude. Caffeine shortened DT in the choice RT task, shortened N200 latency at right hemisphere sites, and shortened N200 latency in the choice RT task in combination with alcohol compared to when alcohol was administered alone. Caffeine also increased P300 amplitude in the choice RT task and reduced the integral of the N500 difference wave at most sites when combined with alcohol. It was concluded that whereas alcohol slows attention allocation and impairs working memory, caffeine accelerated response-related decisions and enhanced cortical arousal.     

中国乒乓球听障奥运选手脑诱发电位特点的研究

探讨中国乒乓球听障奥运队员视觉诱发电位P100和事件相关电位P300的特点,为该项目运动员的选材和机能学评定提供参考。采用上海海神医疗电子仪器厂生产的NDI-200（海神号）神经电检诊仪,对参加2013年7月在保加利亚举行的第22届夏季听障奥林匹克运动会的8名中国乒乓球听障奥运选手和74名常人大学生的视觉诱发电位和视觉事件相关电位进行了记录、分析比较。奥运选手组和对照组之间视觉诱发电位P100波幅和潜伏期均无显著性差异（P＞0．05）。奥运选手组与对照组相比,视觉事件相关电位P300表现为：Cz点的波幅呈极显著性增加（P＜0．01）、Fz点的波幅呈显著性增加（P＜0．05）、Pz点的波幅有一定的增加（P＝0．061）;Pz点的潜伏期呈极显著性缩短（P＜0．01）;Pz、Cz、Fz点的反应时均呈极显著性缩短（P＜0．01）。听障乒乓球运动员和常人对照组之间视觉诱发电位P100波幅和潜伏期均无显著性差异;视觉事件相关电位P300表现为波幅增加、潜伏期缩短、反应时缩短的特点。     

Source Localisation of Visual Evoked Potentials in Congenitally Deaf Individuals

Previous studies have suggested that individuals deprived of auditory input can compensate with specific superior abilities in the remaining sensory modalities. To better understand the neural basis of deafness-induced changes, the present study used electroencephalography to examine visual functions and cross-modal reorganization of the auditory cortex in deaf individuals. Congenitally deaf participants and hearing controls were presented with reversing chequerboard stimuli that were systematically modulated in luminance ratio. The two groups of participants showed similar modulation of visual evoked potential (VEP) amplitudes (N85, P110) and latencies (P110) as a function of luminance ratio. Analysis of VEPs revealed faster neural processing in deaf participants compared with hearing controls at early stages of cortical visual processing (N85). Deaf participants also showed higher amplitudes (P110) than hearing participants. In contrast to our expectations, the results from VEP source analysis revealed no clear evidence for cross-modal reorganization in the auditory cortex of deaf participants. However, deaf participants tended to show higher activation in posterior parietal cortex (PPC). Moreover, modulation of PPC responses as a function of luminance was also stronger in deaf than in hearing participants. Taken together, these findings are an indication of more efficient neural processing of visual information in the deaf, which may relate to functional changes, in particular in multisensory parietal cortex, as a consequence of early auditory deprivation.     

帕金森病患者VEP、BAEP及SEP的测定

目的：研究帕金森病（PD）患者视觉诱发电位（VEP）、脑干听觉诱发电位（BAEP）及体感诱发电位（SEP）的变化并推测其发生机制。方法：选择2008年1月至2013年1月在昆明医学院第一附属医院神经内科门诊及住院的80例PD患者作为PD组,50例健康对照者作为对照组。应用神经电生理检查仪分别对PD患者和健康者进行VEP、BAEP和SEP检测,并进行比较。结果：PD组VEP的P100潜伏期（115．1±10．6）ms较健康对照组（103．2±9．0）ms明显延长（P〈0．01）,P100波幅（6．25±3．02）弘V较健康对照组（7．70±2．62）pV增高（P〈0．05）;PD组BAEP的I、Ⅱ、Ⅲ波的潜伏期和Ⅲ-V及I—V峰间期较对照组明显延长（P〈0．05）;SEP各波潜伏期及波幅两组比较差异无显著意义。结论：PD患者的VEP和BAEP均有不同程度的改变,提示PD患者可能伴有脑干听觉传导通路与视觉俜导诵略的桶害．     

Effects of Attention on Pattern-Reversal Visual Evoked Potentials: Foveal Field Stimulation Versus Peripheral Field Stimulation

The effects of foveal field attention on pattern reversal visual evoked potential (VEP) were investigated in thirteen normal subjects. Conventional monocular VEP was recorded during the three conditions of control, foveal concentration and reaction time task. Three patterns of checkerboard, which were full field (radius, 0-9 degrees), peripheral field (2.5-9 degrees) and foveal field (0-2.5 degrees), were presented for the stimulation in each condition. The P100 and N145 amplitude of the peripheral field VEP were significantly smaller during the concentration and the reaction time task conditions than that in the control session, while the foveal field VEP amplitudes were enhanced in the concentration and reaction time tasks conditions. The full field VEP amplitudes were not significantly changed by the conditions. We concluded that the act of concentration to the foveal field or the task requiring attention to the foveal field, enhanced the VEP response to foveal field stimulation and suppressed the VEP to the peripheral field. A gating effect in area V1 was speculated, although extra-striate cortex might contribute.     

新生儿高胆红素血症闪光视觉诱发电位的检测

应用视觉诱发电位仪对２５例高胆红素血症（简称高胆）新生儿进行了闪光视觉诱发电位（ｒｉｓｕａｌ ｅｖｏｋｅｄ ｐｏｔｅｎｔｉａｌｓ ｔｏ ｆｌａｓｈ,Ｆ－ＶＥＰ）的检测,同时测定了２０例正常新生儿作为对照。结果表明：１．高胆新生儿Ｆ－ＶＥＰ主波潜伏期延长,与正常新生儿比较有显著性差异;２．高胆新生儿胆红素浓度越高,Ｆ－ＦＶＥＰ潜伏越长。提示高胆对视觉神经通道有毒性作用,胆红素浓度越高,毒性损害越大,     

Comparison of human motor cortical projections to abdominal muscles and intrinsic muscles of the hand

Summary Percutaneous electrical stimulation of the motor cortex was used to activate rapidly conducting corticofugal pathways to human abdominal muscles. Following cortical stimulation the response latencies for the abdominal muscles were similar to those for limb muscles which are a similar distance from the motor cortex. Cortically evoked responses recorded from the abdominal muscles had the same latency and similar amplitude during several voluntary tasks including expiration, expulsive manoeuvres and trunk flexion. Responses could also be evoked when the chemical drive to breathe was increased by rebreathing. In addition, the properties of the cortical projection to muscles of the abdominal wall were directly compared with those of the projection to the intrinsic muscles of the hand. The latencies of responses in abdominal muscles and intrinsic muscles of the hand were measured during static contractions over a range of strengths in the same subjects (0–100% maximal voluntary contraction, MVC). For both muscle groups, cortically evoked muscle responses of minimal latency occurred when background contractions reached 10–20% MVC with responses of maximal amplitude at 60% MVC. The variability in latency of fifty consecutive responses were similar for the two muscle groups. Furthermore, post-stimulus time histograms for 4 rectus abdominis motoneurones revealed a brief initial excitatory peak of 1.15ms duration (range 0.96–1.34ms) following cortical stimulation. The characteristics of this peak are the same as reported for motoneurones of intrinsic hand muscles. These findings demonstrate a powerful rapidly conducting pathway from the motor cortex to the human abdominal muscles. This pathway has many of the same properties as the monosynaptic corticospinal projection to the distal muscles of the upper limb.     

帕金森病患者的视觉诱发电位研究

目的:观察帕金森病(PD)患者视觉诱发电位(VEP)的改变及其临床意义。方法:选取昆明医学院第一附属医院神经内科2008年1月～2010年3月期间收治的48例帕金森病患者作为观察组,同时选取45例在昆明医学院第一附属医院神经内科健康体检的志愿者作为对照组,应用丹麦Dantec公司生产的Keypoint4导诱发电位仪对两组受试者进行视觉诱发电位(VEP)的检测并进行比较。结果:观察组视觉诱发电位的P100潜伏期为(116.8±11.2)ms,P100波幅为(6.52±2.87)μV,对照组视觉诱发电位的P100潜伏期为(104.8±10.1)ms,P100波幅为(7.68±3.02)μV,两组P100潜伏期经比较,差异有统计学意义(P<0.05),两组P100波幅差异不显著;观察组P100潜伏期与病程及病情严重程度均呈正相关(P<0.05)。结论:帕金森病患者的视觉诱发电位有一定程度的改变,提示帕金森病患者可伴有视觉传导通路的损害,视觉诱发电位可作为患者疾病早期诊断及病情发展、判断预后的客观的评价标准。     

Origin of the secondary response induced by flash stimulation under barbiturate anesthesia in the rabbit

The photically evoked secondary response of the visual cortex was studied in a rabbit anesthetized with pentobarbital sodium. The following results were obtained: 1) The secondary response (P2) under anesthesia was a simple positive potential having a long latency and resembled the primary response (P1) in waveform. 2) The latency of P2 shortened gradually as the recovery from anesthesia proceeded. 3) P2 was usually smaller than P1 in amplitude when evoked with a strong flash, but larger than P1 when evoked with a weak flash. 4) Electrical stimulation of the superior colliculus (SC) induced in the visual cortex a positive potential which had a long latency comparable to that of P2. On the contrary, stimulation of the lateral geniculate body (LGB) evoked a short latency, positive potential similar to P1, but failed to evoke a positive potential comparable to P2. 5) A partial lesion of LGB led to a decrement of P1, while lesion of SC resulted in a decrement of P2. 6) Cooling of SC resulted in a rapid reduction and disappearance of P2 as well as the negative potential in SC. 7) There were a considerable number of visual cortical neurons which fired commonly during the phases of P1 and P2. These results suggest that P2 might be derived through the extrageniculo-cortical system which is relayed at SC. The mechanism by which P2 was manifested under anesthesia was discussed.     

焦虑症患者VEP及AEP临床研究

目的：观察焦虑症患者听觉诱发电位(AEP)及视觉诱发电位(VEP)的特点。方法：对30例符合CCMD-Ⅱ-R诊断标准的焦虑症患者进行VEP和AEP检查，并以30例正常人作对照。结果：VEP在Fz及Cz处的P2、P3波幅明显降低，在Cz处N1潜伏期延长；AEP在Cz及P2处的P2、P3波波幅明显降低，N1潜伏期延长，在Cz处P2潜伏期延长。结论：焦虑症患者的VEP、AEP有波幅降低，潜伏期延长。     

眼外伤性视神经挫伤患者的早期视觉诱发电位分析

目的 :探讨视觉诱发电位 (VEP)在眼外伤性视神经挫伤中的应用价值。方法 :对 6 8例临床诊断为外伤性视神经挫伤的患者进行VEP测定 ,并与自体健侧眼或正常对照组进行对照。结果 :6 8例患者中单眼挫伤者 6 2例 ,双眼挫伤者 6例 ,共 74眼 ,VEP检查结果均有不同程度的异常。其中有 2例 3眼VEP波幅明显降低 (4 % ) ,单纯波幅异常降低者 5 0例 5 3眼 (71% ) ,波幅降低伴有峰潜伏期延长者 16例 18眼 (2 5 % )。所有外伤性视神经挫伤与自体健侧眼和正常对照比较 ,P10 0波幅差异有显著意义 (P <0 0 1) ,而P10 0峰潜伏期仅有 16例稍有延长 ,与正常值比较无明显差异 (P >0 0 5 )。结论 :VEP对眼球钝挫伤后视神经损伤的检出有较高的敏感性 ,因此对于眼外伤性视神经挫伤中的早期诊断 ,疗效观察 ,预后评估有着重要价值     

Electrocortical signs of word categorization in saccade-related brain potentials and visual evoked potentials

Visual evoked potentials (VEPs) elicited by foveal presentation of words were compared to brain potentials evoked by the same words in a condition where subjects had to make a saccadic eye movement in order to perceive the words (saccade-related brain potentials, SRPs). Subjects had to categorize the words responding with a button press to stimuli belonging to the target (infrequent, P = 0.2) category. The VEP and SRP waveforms showed divergences in the early (up to 250 ms) components, but a marked similarity between the late components. Principal Component Analysis also revealed the same relationship between the two types of brain responses. Peak latency of the late SRP components measured from saccade offset showed an apparent processing advantage over the corresponding late components of VEPs. The N3 component, indexing semantic processing of visual patterns, peaked between 310 and 375 ms in the SRPs, while in the VEPs it appeared between 410 and 470 ms. The P4 component, associated with final stimulus evaluation, showed a similar latency benefit in favour of SRPs (420-500 ms vs 530-590 ms in VEPs). The mean reaction time was 74 ms shorter in the eye movement condition (measured from saccade offset) than in the VEP condition (703 vs 777 ms). The question of what kind of processes may contribute to the differences in mean RTs and to the latencies of the late components between the two conditions are discussed. We suggest that the late components (P3, N3 and P4) of the VEP and the SRP, respectively, index identical brain processes.