电生理监测在颅内动脉瘤夹闭术中的应用及临床意义

目的研究开颅夹闭颅内动脉瘤手术对脑干听觉诱发电位（BAEP）、躯体感觉诱发电位（SEP）和脑电图3项电生理指标的影响及临床意义.方法在25例颅内动脉瘤患者的开颅夹闭术中,进行BAEP、SEP和脑电图实时监测,观察手术操作对神经电生理指标的影响.结果手术操作均不同程度引起BAEP、SEP及脑电图的变化.其中BAEP的Ⅰ、Ⅲ、Ⅴ波的潜伏期延长0.8～1.0ms,Ⅰ～Ⅲ、Ⅲ～Ⅴ波峰间期延长0.3～0.5 ms,Ⅰ、Ⅴ波幅电位较术前降低50%左右;SEP的N20、P25潜伏期延长3～5 ms,波幅较术前降低50%.结论术中动态监测BAEP Ⅰ、Ⅲ、Ⅴ波的潜伏期、Ⅰ～Ⅲ、Ⅲ～Ⅴ波峰间期及Ⅰ、Ⅴ波电位变化,SEP的N20、P25潜伏期、电位变化、脑电图波幅和频率电生理的敏感变化,对了解术中有无脑缺血,灵活调整断流时间及手术方式具有重要的指导意义.     

老年轻度认知功能损害的脑诱发电位变化及其发展为痴呆的预测因素

目的检测老年轻度认知功能损害（MCI）患者的脑诱发电位变化，探索其发展为痴呆的脑诱发电位预测因素。方法前瞻性对照研究。对象为患轻度认知功能损害的老年人（MCI组）和认知功能正常的老年人（NC组）两组。结果23例MCI和29例NC完成了基线脑诱发电位检查。与NC组相比，MCI组的听觉脑干反应波V绝对波幅和P300的P3靶波幅降低有统计学意义（P〈0．01）。多元逐步判别分析显示听觉脑干反应波V绝对波幅和P300的P3靶波幅的判别具有统计学意义（P〈0．01），两组判别总正确率为75％，但Logislic回归分析未发现脑诱发电位指标对MCI是否发展为痴呆有显著性预测作用。结论脑诱发电位检测有助于了解MCI的脑电生理变化，听觉脑干反应波V绝对波幅和P300的P3靶波幅的降低对MCI具有诊断价值。本研究未证实4种检测的脑诱发电位指标对预测MCI发展为痴呆有统计学意义。     

卒中后单侧空间忽略患者的空间注意加工特点分析

目的通过比较右侧卒中后单侧空间忽略(USN)患者与正常人事件相关电位(ERP)行为学检查结果和P1、N1、P300的波幅及潜伏期,研究USN患者的空间注意加工特点。方法回顾性连续纳入首都医科大学宣武医院康复医学科2012年4月至2013年4月收治的右侧卒中后USN患者10例(USN组),选择年龄、性别与USN组匹配的正常受试者10例(正常组)。利用ERP记录两组受试者执行视觉Oddball范式任务时的脑电变化。分析比较两组靶刺激出现在左侧(左靶)、右侧(右靶)时的反应时间及正确率;对靶刺激出现在左侧、右侧的ERP各成分(P1、N1、P300)的波幅及潜伏期进行重复测量的多因素方差分析,探讨卒中后USN的发生机制。结果 USN组靶刺激出现在左侧和右侧时正确率均低于正常组[左靶:(17.7±7.5)%比(98.5±7.5)%,P0.01;右靶:(88.5±2.0)%比(99.0±2.0)%,P=0.002]。两组之间P1波幅差异无统计学意义(F=1.104,P=0.307);当靶刺激出现在左侧时,USN组右半球N1波幅较正常组降低[(-0.3±1.1)μV比(-5.8±1.1)μV;P=0.001];当靶刺激出现在右侧时,USN组N1波幅较正常组降低[(-1.8±1.0)μV比(-6.0±1.0)μV;F=9.799,P=0.006];USN组左靶P300波幅较正常组降低[(1.0±1.1)μV比(7.2±1.1)μV;P=0.001]。与正常组比较,USN组P1(右半球)[(136.7±3.8)ms比(122.1±3.8)ms;P=0.013]、N1[(179.7±2.0)ms比(172.8±2.0)ms;F=5.775,P=0.027]、P300[(490±12)ms比(402±12)ms;F=27.310,P0.01]各波的潜伏期均延长。结论 USN患者在空间注意加工过程中,无论对来自左侧的刺激还是对来自右侧的刺激,其信息加工处理均有一定程度的受损。     

肠易激综合征患者饮冰水及直肠扩张脑诱发电位的研究

目的　通过记录并比较直肠扩张脑诱发电位 (CEP)的特征及饮冰水后CEP的改变 ,探讨肠易激综合征 (IBS)患者内脏高敏感性的发生机制 ,旨在进一步获得IBS感觉传入通路异常的客观依据。方法　根据罗马Ⅱ标准选择女性IBS患者 2 0例 ,其中腹泻型 10例 ,便秘型 6例 ,腹泻 便秘交替型4例 ,另设 12例女性健康志愿者为对照组 ,对其进行快速直肠气囊扩张 ,首先测出每例受试者感觉阈值 ,用该阈值空气体积作为刺激 (频率 1Hz,连续 10 0次 ,休息 10min ,重复 1次 ) ,启动并记录两组受试者CEP的变化。随后 ,每例受试者饮 4℃冰水 2 2 0ml,2 0min后重复上述步骤。结果　直肠节律性机械扩张引出可识别、复制的CEP。与健康对照者 [(87± 17)ms,(14 0± 2 3)ms ,(198± 31)ms]相比 ,IBS患者N1、P1、N2 潜伏期 [(6 9± 15 )ms,(12 1± 2 1)ms,(177± 2 4 )ms) ]明显缩短 (P <0 .0 5 ) ;腹泻型较便秘型IBS患者CEP潜伏期明显缩短 (P <0 .0 5 ) ;饮冰水后 ,IBS患者N1、P1、N2 潜伏期缩短 ,与饮冰水前相比差异有显著性 [分别为 (5 4± 16 )ms,(10 8± 2 0 )ms,(16 1± 2 4 )ms比 (6 9± 15 )ms,(12 1± 2 1)ms,(177± 2 4 )ms;P <0 .0 5 ],而健康对照组饮冰水后CEP无明显变化 ,两组CEP波幅无明显改变。结论　IBS患者经直肠节律性     

非糜烂性胃食管反流病患者酸灌注及食管扩张脑诱发电位的研究

目的研究非糜烂性胃食管反流病(NERD)患者和正常人食管扩张刺激(OD)-脑诱发电位(CEP)的特征及食管酸灌注后 CEP 的改变,探讨 NERD 患者食管内脏高敏感性的发生机制。方法10例健康志愿者和21例 NERD 患者参与试验;采用 Synectics 内脏刺激器/电子气压泵和带有低顺应性气囊及多个灌注式压力通道的导管给食管以时相性扩张刺激和酸灌注;利用食管气囊扩张术检测受试者食管最大耐受痛阈,用75%最大疼痛耐受容积作为诱发刺激的强度(刺激频率为12次/min,连续64次);采用 OD-CEP 系列技术记录并分析食管酸灌注前后 NERD 患者和正常人 CEP 的变化。组间比较采用 t 检验,多组间比较采用单因素方差分析。结果食管时相性机械扩张刺激诱发出可识别、可重复、多峰的 CEP 波形,以 NP 型为主。正常对照者 N1、P1、N2波潜伏期分别为(246±77)、(388±84)和(502±78)ms,NERD 患者 CEP 波形变异性大,其 N1、P1、N2波潜伏期分别为(192±46)、(293±76)和(440±79)ms,较对照组明显缩短(P 值均<0.05);P1-N2峰间波幅明显增加[(6.2±1.9)μV 比(7.8±3.2)μV,P<0.05]。食管酸灌注能明显缩短 NERD 患者 N1、P1、N2波潜伏期,与酸灌注前相比差异有统计学意义(P 值均<0.05),且酸灌注后 NERD 患者 P1-N2皮层波幅值较酸灌注前显著增加(p<0.05),健康对照组除 CEP 的 N1波潜伏期较对应基线值显著降低(P=0.05)外,其余 CEP 参数均无明显改变。结论 NERD 患者存在食管对机械和酸刺激的高敏感性及食管-中枢内脏感觉传导通路失凋。     

老年人瞬目反射的测定和分析

目的　了解老年人瞬目反射 (BR)的正常分布及变异。　方法　对 30例 (6 0侧 )老年人及 2 9例 (5 8侧 )非老年人进行瞬目反射的测定并进行比较。　结果　老年组BR早期反应R1的潜伏期为 (10 2 8± 0 39)ms ,波幅为 16 2 88μV ;同侧晚期反应R2 的潜伏期为 (32 86± 2 81)ms,波幅为2 10 72 μV ;对侧晚期反应R2 ’的潜伏期为 (33 33± 2 90 )ms ,波幅为 15 6 32 μV。非老年组R1的潜伏期为 (9 98±± 0 87)ms,波幅为 2 10 2 2 μV ;R2 的潜伏期为 (2 9 5 2± 2 2 4)ms,波幅为 2 2 8 15 μV ;R2 ’的潜伏期为 (2 9 94± 2 2 9)ms ,波幅为 189 5 0 μV。两组比较 ,各波间潜伏期差异均有非常显著性 (均为P <0 0 1)。　结论　BR的测定简便、无创、易行 ,随年龄增长其潜伏期延长 ,应建立老年人的BR正常值。     

右侧卒中患者的视空间注意加工特点分析

目的通过比较右侧卒中后视空间忽略(VSN)患者与无VSN患者事件相关电位(ERP)行为学检查结果和各成分(P1、N1、P2、N2、P300)的波幅及潜伏期,研究VSN患者的视空间注意加工特点,进一步探索VSN的发生机制。方法回顾性连续纳入首都医科大学宣武医院康复医学科自2016年2月至2017年2月收治的右侧卒中后VSN患者9例(VSN组),右侧卒中经忽略行为学量表筛查无VSN患者10例(非VSN组)。利用ERP记录2组受试者执行视觉Oddball范式任务时的脑电变化。分析比较2组靶刺激出现在左侧(左靶)、右侧(右靶)时的反应时及正确率;对靶刺激出现在左侧、右侧的ERP各成分(P1、N1、P2、N2、P300)的波幅及潜伏期进行重复测量的多因素方差分析。结果 VSN组左靶、右靶的正确率[分别为(17.7±7.8)%、(88.5±2.2)%]明显低于非VSN组[分别为(92.4±7.8)%、(96.7±2.2)%,均P0.05],VSN组右靶反应时[(586±119)ms]明显长于非VSN组[(483±60)ms,P=0.025]。两组之间P1、N1、P2、N2各波的波幅差异无统计学意义(均P0.05);靶刺激出现在左靶时,VSN组P300波幅[(1.2±0.6)μV]小于非VSN组[(4.6±0.6)μV,P=0.001]。右半球VSN组P1潜伏期[(135.7±3.8)ms]较非VSN组[(128.2±2.8)ms]明显延长(P=0.021),而N1、N2、P300潜伏期两组间差异无统计学意义(均P0.05)。结论与右侧卒中非VSN患者相比,VSN患者主要表现为空间注意加工的晚期过程受损。     

电生理指标联合应用在颅内巨大动脉瘤手术中的作用

目的研究躯体感觉诱发电位(SEP)、脑电图、脑干听觉诱发电位(BAEP)联合应用在颅内巨大动脉瘤手术治疗中的影响及临床意义。方法分别对23例颅内巨大动脉瘤患者进行手术直接夹闭或动脉瘤孤立加旁路移植手术,同时行SEP、脑电图和BAEP实时监测,观察手术操作对其的影响。结果 23例患者行颅内巨大动脉瘤手术操作时,均不同程度引起SEP、脑电图和BAEP的变化。其中SEP的N20、P25潜伏期延长3～5 ms,波幅较术前降低50%;BAEP的Ⅰ、Ⅲ、Ⅴ波潜伏期延长0.7～1.0 ms,Ⅰ～Ⅲ、Ⅲ～Ⅴ波峰间期及Ⅰ、Ⅴ波幅电位较术前降低30%～50%以上。结论术中动态监测SEP、脑电图和BAEP的电位变化,可以提示颈动脉阻断后的脑灌注状态,对调整手术时间及手术方式具有重要的指导意义。     

一种新的人长潜伏期体感诱发电位提取方法

目的 用自参考自相关自适应干扰对消理论和技术(AAA-ICT)提取人长潜伏期体感诱发电位.方法 用电刺激器刺激人体腕正中神经体表处,刺激信号为波宽0.1～0.9 ms的单脉冲方波信号,用体表Ag/AgCl电极采集,借助于自参考自相关自适应干扰对消技术来处理采集信号.结果 获得单次提取和叠加平均的体感诱发电位信号.结论 AAA-ICT提取到的长潜伏期体感诱发电位避免了传统叠加平均理论的缺陷,能给出长潜伏期体感诱发电位的潜伏期和波幅的变异特征,为某些神经精神疾病的诊断和鉴别诊断提供新的指标.     

遗忘型轻度认知损害患者工作记忆事件相关电位研究

目的研究遗忘型轻度认知损伤患者的工作记忆损害机制及敏感指标。方法将2004年10月至2005年12月解放军总医院门诊和住院15例遗忘型轻度认知损害患者和15名年龄、性别、受教育年限匹配的正常老年对照参与本研究。事件相关电位检查采用视觉刺激模式，成对的简单平面图形先后呈现，受试者比较刺激对是否相同，同时记录32导脑电、正确反应率及反应时间。结果患者组与正常老年组操作行为差异无显著性。刺激相同即匹配状态下两组P300波形分布均以顶部为著，事件相关电位P300潜伏期及波幅差异无显著性（F1．28=1．0324，P=0．3183；F2.42=0．543，P=0．585）。刺激相异即冲突状态下事件相关电位N270主要分布在前头部，患者组N270潜伏期较正常老年组明显延长（F1．28=25．3264），波幅差异无显著性（F1．28=0.507，P=0.482）。脑电地形图与上述结果相一致。结论遗忘型轻度认知损害患者前额ERP成分N270的变化可能反映了其工作记忆中央执行系统损害。N270在检测这一损害时较P300敏感。     

Cortical and spinal evoked potential response to electrical stimulation in human rectum

AIM: To study a novel technique to record spinal and cortical evoked potentials (EPs) simultaneously in response to electrical stimulation in the human rectum. METHODS: Eight male and nine female healthy volunteers participated. Stimulating electrodes were attached to the rectal mucosa at 15 cm and 12 cm above the dentate line. Recording skin electrodes were positioned over vertebrae L4 through S2. The electrical stimulus was a square wave of 0.2 ms duration and the intensity of the stimulus varied between 0 and 100 mA. EP responses were recorded using a Nicolet Viking IV programmable signal conditioner.RESULTS: Simultaneous recording of cortical and spinal EPs was obtained in > 80% of the trials. The EP responses increased with the intensity of the electrical stimulation, were reproducible overtime, and were blocked by application of Lidocaine jelly at the site of stimulation. The morphology (N1/P1), mean ± SD for latency (spinal N1, 4.6 ± 0.4 ms; P1, 6.8 ± 0.5 ms; cortical N1, 136.1 ± 4.2 ms; P1, 233.6 ± 12.8 ms) and amplitude (N1/P1, spinal, 38 ± 7 μV; cortical 19 ± 3 μV) data for the EP responses were consistent with those in the published literature. Reliable and reproducible EP recordings were obtained with the attachment of the electrodes to the rectal mucosa at predetermined locations between 16 and 8 cm above the anal verge, and the distance between the attachment sites of the electrodes (the optimal distance being approximately 3.0 cm between the two electrodes). CONCLUSION: This technique can be used to assess potential abnormalities in primary afferent neural pathways innervating the rectum in several neurodegenerative and functional pain disorders.     

Visceral afferent hypersensitivity in irritable bowel syndrome—evaluation by cerebral evoked potential after rectal stimulation

OBJECTIVES: Gut hypersensitivity has been shown to be present in irritable bowel syndrome. The current study sought to determine the involvement or hypersensitivity of the gut afferents, objectively, by recording cerebral evoked potential after rectal stimulation. METHODS: In 13 patients with irritable bowel syndrome and nine healthy controls, rectal perception thresholds to electrical stimulation were measured, and cerebral evoked potentials were recorded from 2 cm behind vertex (Cz') after rectal stimulation electrically (frequency 1 Hz, duration 0.5 ms) at an intensity 50% above perception threshold and with filter setting 1-250 Hz. RESULTS: Perception thresholds to rectal electrical stimuli in patients with irritable bowel syndrome were lower than controls (p < 0.05). Rectal stimulation led to recognizable and reproducible cerebral evoked potentials. P1, N1, P2 latencies in patients with irritable bowel syndrome were shorter than that in controls (p < 0.05). P1/N1 amplitude was greater in patients with irritable bowel syndrome than in controls (p < 0.05). CONCLUSIONS: The shorter latency and increased amplitude of cerebral evoked potential after rectal stimulation in patients with irritable bowel syndrome compared to controls provide objective evidence supporting visceral afferent hypersensitivity as the underlying mechanism in irritable bowel syndrome.     

Influence of high-dose opioid anesthesia on posterior tibial nerve somatosensory cortical evoked potentials: Effects of fentanyl,sufentanil, and alfentanil

The effects of high doses of fentanyl (group F), sufentanil (group S), and alfentanil (group A) on posterior tibial nerve somatosensory cortical evoked potentials were studied in 30 patients scheduled for elective valve replacement surgery. Anesthesia was induced with either fentanyl, 75 μg/kg, sufentanil, 5 μg/kg, or alfentanil, 125 μg/kg. The lungs were ventilated with oxygen/air. A bolus dose of fentanyl, 25 μg/kg, was given 30 minutes after induction of anesthesia in group F. Anesthesia was maintained with a continuous infusion of sufentanil, 5μg/kg/h, in group S, or alfentanil, 500 μg/kg/h, in group A. Latencies of the peaks of the primary cortical complex (P1, N1, 132) increased by 1 to 2 ms after induction of anesthesia, although this was significant (P < 0.01) only for P1 and N1 in groups F and S. N2 latency increased significantly (P < 0.01) by 6 to 10 ms in all groups. P1-N1 amplitude did not change after induction of anesthesia. N1-P2 amplitude decreased significantly (P < 0.01) to 60%–70% of preinduction values in groups F and S. P2-N2 amplitude decreased significantly (P < 0.01) to 60%–70% of preinduction values in all groups. P1, N1 and P2 latencies did not change significantly from the post-induction values in the period preceding cardiopulmonary bypass (75 ± 16 minutes) in groups F and S. In group A significant changes were observed only for N1 and P2 latency (P < 0.01). During this period there was a further gradual increase in N2 latency and amplitudes remained stable, except P1-N1 amplitude in group F, which decreased significantly (P < 0.05). A bolus dose of fentanyl, 25 μg/kg, given in group F at 30 minutes after induction of anesthesia did not change latencies and amplitudes. No significant differences in latency or amplitude were found at any time among the three study groups. It is concluded that anesthesia with high doses of fentanyl, sufentanil, or alfentanil is a suitable technique when intraoperative monitoring of posterior tibial nerve somatosensory cortical evoked potentials is indicated.     

Spinal and muscular evoked response following single stimulation of the motor cortex of the rat

The general characteristics of motor evoked potentials recorded from muscle and spinal cord in response to single electrical stimulation of motor cortex were examined in 30 rats. 5 other rats were additionally examined before and after full muscle relaxation, to differentiate the volume-conducted muscle response from spinal cord responses. The first positivity (P1) recorded from the lower thoracic cord following anodal stimulation was 1.1 +/- 0.1 ms and the second positivity (P2) was 2.1 +/- 0.2 ms. P1 was present in 11 animals and P2 in 20. The later components after 2.3 ms latency recorded from the epidural spinal electrode were lost with full muscular relaxation and seem to originate from volume conducted muscular activity. A relatively stable early MEP muscle response (6.1 +/- 0.9 ms) was observed in contralateral lower extremity muscles of all animals. Following this early response, a late MEP muscle response (16.0 +/- 1.9 ms) has been recorded in 43% of all animals. This relatively inconstant and multiphasic late muscle response disappeared during vibration of same extremity tendons and has similar characteristics as Hoffmann's reflex response. Additionally, with increasing stimulus intensities, the amplitude ratio of early to late response was similar to M response/H reflex amplitude ratio. The results suggest that the late MEP muscle response is probably the result of a reflex response caused by the first/early descending volley and traveled back to the spinal cord possibly through the Ia afferents similar to that in the H-reflex.     

阻塞性睡眠呼吸暂停低通气综合征患者膈肌对经颅磁刺激的反应

目的 探讨阻塞性睡眠呼吸暂停低通气综合征(OSAHS)患者经颅磁刺激(TMS)膈肌运动诱发电位(MEP)的变化及可能机制.方法 2005年6月至2006年6月就诊广州医学院第一附属医院呼吸疾病研究所的健康体检者及鼾症患者,分为健康对照组16例,单纯鼾症组7例,OSAHS轻中度组13例及重度组16例,均使用TMS结合经颈椎棘突磁刺激(CMS)及多导食管电极测定右侧膈肌MEP的潜伏期、幅值和中枢运动传导时间(CMCT),5例OSAHS患者经有效鼻持续气道正压通气(nCPAP)治疗超过2个月后复查上述指标.采用SPSS 12.0统计软件进行数据分析,检测结果 以x±s表示.结果 OSAHS重度组右侧膈肌MEP的幅值为(152±116)μV,明显低于健康对照纽的(414±201)μV、单纯性鼾症组的(352±99)μV及OSAHS轻中度组的(372±206)μV;其膈肌MEP的潜伏期和CMCT分别为(18.1±1.8)和(10.6±1.8)ms,与健康对照组的(13.9±1.6)和(7.7±1.7)ms相比,单纯性鼾症组的(14.6±1.6)和(8.1±1.6)ms以及轻中度组的(15.4±2.7)和(9.0±2.2)ms明显延长.膈肌MEP的幅值、潜伏期及CMCT与微醒觉指数、呼吸暂停最长时间、夜间最低脉搏容积血氧饱和度(SpO2)、低氧指数、SpO2<90%占总睡眠时间比例以及呼吸暂停低通气指数(AHI)均具有相关性.5例重度OSAHS患者经nCPAP治疗超过2个月后,膈肌MEP的潜伏期较治疗前缩短,分别为(17.5±0.6)和(15.5±0.7)ms.结论 OSAHS患者膈肌MEP的潜伏期和CMCT均延长,而MEP的振幅降低,这些变化可能与反复夜间低氧、二氧化碳潴留及睡眠结构紊乱有关.     

Oesophageal sensation assessed by electrical stimuli and brain evoked potentials--a new model for visceral nociception.

Sensory thresholds and brain evoked potentials were determined in 12 healthy volunteers using electrical stimulation of the oesophagus 28 and 38 cm from the nares. The peaks of the evoked potentials were designated N for negative deflections and P for positive. Continuous electrical stimulation (40 Hz) at the 38 cm position resembled heartburn (five of 12 subjects) while non-specific ('electrical') sensations were provoked at 28 cm (10 of 12). Thresholds of sensation and of pain were lower at the initial than the second determination, but did not differ with respect to stimulation site. The pain summation threshold to repeated stimuli (2 Hz, 5 stimuli) was determined for the first time in a viscus. This threshold was lower than the pain threshold to single stimuli at 38 cm (p < 0.02). Evoked potential latencies did not change significantly over a six month period while the N1/P2 amplitude was higher at the first measurement (p < 0.05). P1 and N1 latencies were significantly shorter 38 cm (medians 100 and 141 ms) than 28 cm from the nares (102 and 148 ms) (p = 0.04 and p = 0.008). Electrical stimulation of the oesophagus may serve as a human experimental model for visceral pain. Longer evoked potential latencies from the proximal compared with distal stimulations provide new information about the sensory pathways of the oesophagus.     

Cerebral response to electric stimulation of the colon and abdominal skin in healthy subjects and patients with irritable bowel syndrome.

BACKGROUND: Visceral hyperalgesia may play an important part in the pathophysiology of the irritable bowel syndrome (IBS). We investigated the neuronal afferent pathways in healthy volunteers and IBS patients by recording evoked potentials (EPs) elicited by electrical stimulation of the colon and abdominal skin inside and outside the referred pain area. METHODS: Six healthy subjects and nine IBS patients met the inclusion criteria. Morphology and topography of EPs to painful electrical stimuli were estimated in the rectosigmoid junction and on the skin inside/outside the referred pain areas. RESULTS: The EPs to painful stimuli of the gut showed a shorter latency and a smaller amplitude of the first positive peak (P1) in the IBS group. The controls had a mid-latency frontal positive component after 100 ms, whereas no reliable early activation was seen in the IBS patients. In controls, a single late (>150 ms) positive component was seen, whereas the late component was biphasic in the IBS group. The EPs to painful stimuli of the two skin areas differed in IBS patients, but not in controls. CONCLUSION: Differences in the EPs to electrical painful stimulation of the sigmoid colon and skin inside/outside the experimentally evoked referred pain area were seen comparing healthy subjects and IBS patients. The results indicate altered central nervous system responses.     

The effect of a reference electrode on the configuration of somatosensory evoked potentials

Early somatosensory evoked potentials to median nerve stimulation were recorded in 6 normal adults from the scalp and the neck. Simultaneous derivations consisted of a recording with a cephalic reference, recordings of both electrodes with a noncephalic reference and an arithmetically subtraction of these potentials. The electrodes were placed over the scalp (P4'), the lower and the upper neck and the reference electrodes over the midfrontal region (Fz), both ears (M1/2) and the contralateral hand. P15/P16 in the P4'-Fz derivation had no identity to the far field potentials (FFP) P13/P14 recorded from the scalp with hand reference. FFP P9 and P11 from the ear lobes was abolished in the P4'-M1/2 derivation and the residual positive waves corresponded to P13 and P14. None of the electrodes picked up a wave equivalent to P15 regardless of the reference electrode. In the neck (CV 7) - scalp derivation NSEP9, 13 and 14 corresponded to the FFP P9, 13 and 14. NSEP11 differed in latency from P11 and N11. There was no latency shift from the lower (CV 7) to the upper (CV 2) neck. NSEP9 and 11 was enhanced in amplitude from CV 7, which resulted from different polarities (N11/P11) over CV 7 and CV 2. These results indicate the necessarity of potential analysis with respect to the activity of the recording electrodes.     

Visual evoked potentials in pattern motion

Our intention was to obtain a visual evoked potential (VEP) consisting only of a movement-related component for the purpose of further investigations of movement detection. This was attempted by selection of appropriate stimulus conditions. Evoked by initial movement a VEP with five typical waves was observed at the human occipital scalp. The N2-wave with a peak latency of 180-200 ms was most prominent. Following results were yielded in the experiments carried out: 1. Adaptation to a pattern movement: The amplitude of N2 and P1 is significantly reduced (Fig. 4). 2. Relation between amplitude and velocity: The experimental data could be approximated by a power function with an exponent of m = 0.3 for N2 and lower m for later waves (Fig. 5). 3. Pattern variation (grating, checkerboard, zig-zag) had no influence on N2 but on P1 and possibly also on later waves (Fig. 6). These results suggest that the wave N2 is movement-related under our experimental conditions. A pattern-related component may additionally be assumed in wave P2. Components, evoked by further reasons, may be included in the waves following N2. Their specification demands supplementary experiments.     

Cerebral Response to Electric Stimulation of the Colon and Abdominal Skin in Healthy Subjects and Patients with Irritable Bowel Syndrome

Background: Visceral hyperalgesia may play an important part in the pathophysiology of the irritable bowel syndrome (IBS). We investigated the neuronal afferent pathways in healthy volunteers and IBS patients by recording evoked potentials (EPs) elicited by electrical stimulation of the colon and abdominal skin inside and outside the referred pain area. Methods: Six healthy subjects and nine IBS patients met the inclusion criteria. Morphology and topography of EPs to painful electrical stimuli were estimated in the rectosigmoid junction and on the skin inside/outside the referred pain areas. Results: The EPs to painful stimuli of the gut showed a shorter latency and a smaller amplitude of the first positive peak (P1) in the IBS group. The controls had a mid-latency frontal positive component after 100 ms, whereas no reliable early activation was seen in the IBS patients. In controls, a single late (> 150 ms) positive component was seen, whereas the late component was biphasic in the IBS group. The EPs to painful stimuli of the two skin areas differed in IBS patients, but not in controls. Conclusion: Differences in the EPs to electrical painful stimulation of the sigmoid colon and skin inside/outside the experimentally evoked referred pain area were seen comparing healthy subjects and IBS patients. The results indicate altered central nervous system responses.