The relationship between reaction time and response variability and somatosensory No-go potentials

We investigated the relationship between reaction time (RT) and response variability and somatosensory Go/No-go potentials. Event-related potentials following electrical stimulation of the second (Go stimulus) or fifth (No-go stimulus) digit of the left hand were recorded from 16 subjects, and Go and No-go stimuli were presented at an even probability. The subjects were instructed to respond to the Go stimuli by pushing a button with their right thumb. We analyzed the correlation between RT and the N140 and P300 components, and between the standard deviation (SD) of RT and the N140 and P300. Neither the amplitude nor latency of the No-go-N140 (N140 evoked by No-go stimuli) or the Go-N140 (N140 evoked by Go stimuli) related significantly with RT and the SD of RT. There was a significant negative correlation between RT and the amplitude of the No-go-P300 (P300 evoked by No-go stimuli) at Fz and C3, indicating that subjects with a shorter RT had a No-go-P300 of larger amplitude. The latency of the Go-P300 (P300 evoked by Go stimuli) at Pz and C3 showed a significant correlation with RT. The SD of RT was significantly correlated with the amplitudes of the No-go-P300 at C3 and Go-P300 at Pz and C4, and the latency of the No-go-P300 at Cz and Go-P300 at Fz, Cz, Pz, C3, and C4. Our results suggest that response speed and variability for the Go stimulus in Go/No-go paradigms affect No-go-related neural activity for the No-go stimulus.     

Changes in the somatosensory N250 and P300 by the variation of reaction time

We investigated the relationship between somatosensory event-related potentials (ERP) and the variation of reaction time (RT). For this purpose, we recorded the ERPs (N250 and P300) in fast- and slow-reaction trials during a somatosensory discrimination task. Strong, standard, and weak target electrical stimuli were randomly delivered to the left median nerve at the wrist with a random interstimulus interval (900–1,100 ms). All the subjects were instructed to respond by pressing a button with their right thumb as fast as possible whenever a target stimulus was presented. We divided all the trials into fast- and slow-RT trials and averaged the data. N250 latency tended to be delayed when the RT was slow, but not significantly. P300 latency was delayed significantly when the RT was slow, but to a much lesser extent than the RT delay, so we concluded that the change of RT was not fully determined by the processes reflected by the somatosensory N250 or P300. Furthermore, the larger and earlier P300 in the fast-RT trials implied that when larger amounts of attentional resources were allocated to a given task, the speed of stimulus evaluation somewhat increased and RT was shortened to a great extent. N250 amplitude did not significantly vary in the two RT clusters. In conclusion, the somatosensory N250 reflects active target detection, which is relatively independent of the modulation of the response speed, whereas the somatosensory P300 could change without manipulation of either the stimulus or the response processing demand. Electronic Publication     

分裂症患者失匹配负波与P300的关系

目的探讨分裂症患者失匹配负波(MMN)与P300的相关性。方法 45例分裂症患者和39例正常对照组采用事件相关脑电位检查,测量MMN和P300潜伏期和波幅,并采用分层多元回归进行分析。结果患者组产生的MMN的潜伏期延长,波幅降低,与正常对照组比较差异均有显著性(t=5.697,9.099;P<0.01),患者组产生的P300的潜伏期延长,与正常对照组比较差异无显著性(t=1.850,P>0.01)。患者组产生的P300波幅降低,与正常对照组比较差异有显著性(t=3.440,P<0.01)。在P300波幅产生的过程中MMN波幅和Group疾病过程的效应被观察到。结论 MMN波幅和Group减少了P300波幅的产生。     

Affective and psychotic symptoms relate to different types of P300 alteration in depressive disorder

BACKGROUND: Previous findings of P300 alterations in depressive disorder have been controversial. We therefore used multivariate methods to study the relationship between P300 and affective and psychotic symptoms in depressive disorder. METHODS: The P300 of 22 psychotropic drug-free depressed out-patients was registered within an auditory oddball paradigm. Affective and psychotic symptoms were evaluated using the depression and psychoticism subscales of SCL-90. The relationship of P300 amplitude and latency with affective and psychotic symptoms was assessed with multiple linear regression analysis and ANOVA. P300 values of the depressed patients were also compared with those of 22 healthy controls. RESULTS: Psychotic symptoms were associated with an overall reduction in P300 amplitude, which was pronounced in the left temporocentral electrode chain (T3, C3, Cz). Psychotic symptoms were also associated with a prolonged P300 latency. Affective symptoms were associated with a relational amplitude reduction at the right temporal scalp sites. There were no statistically significant differences in P300 amplitude or latency between depressed and control-subjects. LIMITATIONS: Rather small number of study subjects. The psychotic scores were low in all subjects. Multiple statistical analyses were used, and no specific a priori hypothesis was tested. CONCLUSIONS: In depressive disorder, affective and psychotic symptoms are associated with different types of P300 alteration, which may indicate different underlying neurobiological processes.     

Modulation of motor cortex excitability by median nerve and digit stimulation

We investigated the time course of changes in motor cortex excitability after median nerve and digit stimulation. Although previous studies showed periods of increased and decreased corticospinal excitability following nerve stimulation, changes in cortical excitability beyond 200 ms after peripheral nerve stimulation have not been reported. Magnetoencephalographic studies have shown an increase in the 20-Hz rolandic rhythm from 200 to 1000 ms after median nerve stimulation. We tested the hypothesis that this increase is associated with reduced motor cortex excitability. The right or left median nerve was stimulated and transcranial magnetic stimulation (TMS) was applied to left motor cortex at different conditioning-test (C-T) intervals. Motor-evoked potentials (MEPs) were recorded from the right abductor pollicis brevis (APB), first dorsal interosseous (FDI), and extensor carpi radialis (ECR) muscles. Right median nerve stimulation reduced test MEP amplitude at C-T intervals from 400 to 1000 ms for APB, at C-T intervals from 200 to 1000 ms for FDI, and at C-T intervals of 200 and 600 ms for ECR, but had no effect on FDI F-wave amplitude at a C-T interval of 200 ms. Left median nerve (ipsilateral to TMS) stimulation resulted in less inhibition than right median nerve stimulation, but test MEP amplitude was significantly reduced at a C-T interval of 200 ms for all three muscles. Digit stimulation also reduced test MEP amplitude at C-T intervals of 200–600 ms. The time course for decreased motor cortex excitability following median nerve stimulation corresponds well to rebound of the 20-Hz cortical rhythm and supports the hypothesis that this increased power represents cortical deactivation. Received: 11 December 1998 / Accepted: 30 April 1999     

P300 in Patients with Unilateral Temporal Lobectomies: The Effects of Reduced Stimulus Quality

The effects of stimulus quality on the amplitude, peak latency, onset latency, and duration of the P300 component of the event-related brain potential were studied in patients with either a left or a right anterior temporal lobectomy and in normal controls. Stimulus quality was reduced by adding "noise" letters to words which signalled either a left or a right hand button press. Consistent with an interpretation that stimulus quality affects the subject's degree of equivocation, P300 peak latency, reaction time, and errors were all inversely related to stimulus quality, whereas P300 amplitude was directly related to stimulus quality. There were no significant differences between normal controls and either patient group for any of the ERP parameters or reaction time. Right temporal lobectomy patients made, however, significantly more errors, particularly on the catch trials, which suggests that they did not process the stimuli as thoroughly and accurately as the subjects in the other two groups. The absence of significant group differences in either the lateral symmetry or overall P300 amplitude extends the evidence against the idea that anterior temporal lobe structures make any substantial contribution to the scalp P300 in a visual discrimination paradigm. Because of observed delays in the onset of P300 in the low-quality stimulus condition, procedures were developed to quantify both P300 onset latency and P300 duration. Reduced stimulus quality significantly increased P300 onset latency whereas P300 duration remained unaffected, indicating that stimulus categorization must occur prior to, and not during, P300.     

痉挛性斜颈体感诱发电位的研究

目的：探讨痉挛性斜颈患者大脑皮层功能的变化。方法：对30例痉挛性斜颈患者刺激正中神经后体感诱发电位（SEP）的P22、N30波潜伏期及P22、N30波幅进行比较分析,30例正常对照组仅在颈部主动向右侧扭转时对双侧P22、N30波幅进行比较分析。结果：病例组SEPP22、N30潜伏期正常,双侧比较差异无统计学意义,头部扭转方向的对侧大脑半球前中央区的P22-N30波幅比明显高于对侧,差异有统计学意义。正常对照组前中央区记录的双侧P22N30波幅比较差异无统计学意义。结论：SEP P22、N30潜伏期正常提示传导通路结构完整,头部扭转方向的对侧大脑半球前中央区的P22-N30波幅比明显高于对侧,提示患者对侧大脑皮层前中央区电活动存在异常的兴奋及抑制,即抑制性减弱,兴奋性增高,N30记录的是刺激正中神经SEP中长潜伏成分,可能来源于运动辅助区,进一步提示患者存在感觉一运动整合功能异常。     

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。     

Brain event-related potentials (ERPs) in schizophrenia during a word recognition memory task.

Impairments of recognition memory for words and attenuation of the ERP 'old-new' effect have been found in patients with left medial temporal lobe damage. If left temporal lobe dysfunction in schizophrenia involves medial structures (e.g. hippocampus), then schizophrenic patients might show similar abnormalities of verbal recognition memory. This study recorded ERPs from 30 electrode sites while subjects were engaged in a continuous word recognition memory task. Results are reported for 24 patients having a diagnosis of schizophrenia (n = 16) or schizoaffective disorder (n = 8) and 19 age-matched healthy controls. Both patients and controls showed the expected 'old-new' effect, with greater late positivity to correctly recognized old words at posterior sites, and there was also no significant difference between groups in P3 amplitude. However, accuracy of word recognition memory was poorer in patients than controls, and patients showed markedly smaller N2 amplitude. Reduced amplitudes of N2 and N2-P3 were associated with poorer performance, with highest correlations over the left inferior parietal (N2) and left medial parietal (N2-P3) region. Moreover, patients failed to show significantly greater left than right hemisphere amplitude of N2-P3 at posterior sites, which was seen for healthy controls. These findings suggest that impaired word recognition in schizophrenia may arise from a left lateralized deficit at an early stage of processing, beginning at 200-300 ms after word onset.     

Normal values of F wave in lower extremities of 73 healthy individuals in Iran

F wave latency has been shown to be a simple and valuable method in evaluation of proximal part of peripheral nerves. According to our previous study of F wave of upper extremity nerves (1), maximum normal F wave latency for the median nerve was 28 ms with stimulation at wrist and 25 ms with stimulation at elbow. These values for the ulnar nerve were 29 ms and 25 ms respectively. Maximum normal difference between right and left F wave latency with wrist stimulation was 2 ms for median nerve and 2.5 ms for ulnar nerve. Maximum normal difference between median and ulnar nerve F latency was 3.5 ms with stimulation at wrist. In this study we measured F wave of lower extremity nerves in 73 healthy individuals in Shiraz. Maximum normal F wave latency for tibial nerve was 55 ms with stimulation at ankle and 46 ms with stimulation at popliteal area. Maximum normal F wave latency for the peroneal nerve was 54 ms with stimulation at ankle and 47 ms with stimulation at fibular head. Mean F ratio for both nerves was 1.29 with stimulation at knee. Maximum normal difference in F wave latency between right and left lower extremities was 3.5 ms with stimulation at ankle and 3 ms with stimulation at knee for the peroneal nerve. These values were 3 ms and 2.5 ms for the tibial nerve respectively. Maximum normal difference in F wave latency between tibial and peroneal nerve was 4 ms with stimulation at ankle and 3 ms with stimulation at knee.     

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.     

Long-term physical exercise and somatosensory event-related potentials

We have compared the occurrence patterns of somatosensory event-related potentials (ERPs) in athletes (soccer players) and non-athletes. ERPs were elicited by two oddball tasks following separate somatosensory stimulation at the median nerve (upper-limb task) and at the tibial nerve (lower-limb task). In the athlete group the N140 amplitudes were larger during upper- and lower-limb tasks and the P300 amplitude and latency were larger and shorter, respectively, during the lower-limb task compared with non-athletes. On the other hand, no significant differences in the P300 amplitude and latency during the upper-limb task were observed between the athlete and non-athlete groups. These results indicate that plastic changes in somatosensory processing might be induced by performing physical exercises that require attention and skilled movements.     

The effect of transcutaneous electrical nerve stimulation on sympathetic skin response

The aim of present study was to determine whether combination of transcutaneous electrical nerve stimulation (TENS) and acupuncture inhibits sympathetic nerve activity in healthy humans. Multiunit efferent postganglionic sympathetic activity was recorded with Toennies set. In this study, the aim was to obtain latency, amplitude and duration of sympathetic skin response (SSR) and skin temperature (ST) from both hands in 15 healthy subjects. Subjects randomly assigned and everybody participated in all the three groups [Control Group (CG), Acupuncture Group (AG) and Nerve Stimulation Group (NSG)]. TENS (2 Hz, 250 microsecond) was applied over the median nerve of the right elbow in NSG for 20 min, either, TENS was applied over (HE-7) point of the right hand in CG (TENS off) and AG (TENS on) for 20 min. SSR (lat, amp, dur) and ST data was recorded before TENS and for immediate, 5 min and 10 min post--TENS. ST was recorded in distal phalanx of index finger of both hands and SSR was recorded from both hands. TENS in CG did not affect ST and SSR following stimulation. TENS applied at AG and NSG caused a significant increase in ST (P = 0.001), significant increase in latency of SSR (P = 0.001), significant decrease in amplitude of SSR (P = 0.001) and no significant changes were observed in duration of SSR (P > 0.05). Then statistical analysis showed differences between both of groups (AG & NSG) for ST and SSR post--TENS. Transcutaneous electrical nerve stimulation inhibits sympathetic nerve activity in healthy humans.     

Habituation of event-related potentials in patients with Parkinson's disease

Auditory event-related potential (ERP) was studied in idiopathic Parkinson's disease (PD) using our new procedures. We examined 12 non-demented patients with PD, and 9 age-matched control subjects. Ninety responses induced by rare stimulation were continuously recorded from Fz, Cz, Pz referred to linked earlobe electrode (A1A2), and were divided into nine blocks (one block = 10 responses) for statistical analysis. We assessed the habituation of auditory ERP to detect delicate changes related to the information processing in PD. N100 and P300 latencies were significantly longer in PD than in control subjects (p<0.05). P300 latency gradually increased with progression of recording blocks in both PD and control subjects, whereas N100 latency increased only in PD. Three way analysis of variance for P300 amplitude revealed significant effects of subject group, recording electrode site, and trial block. P300 amplitude was smaller in PD than in control subjects. Significant negative correlation between P300 amplitudes and block numbers were observed at Cz and Pz in PD, and at Fz in the control group. Previous reports as well as present results suggest that prolongation of N100 latency might be related to frontal lobe dysfunction, and abnormality of P300 to dysfunction in both the frontal lobe and hippocampus in PD.     

Subclinical neuropathy in children with inherited haemostasis disorders.

Motor and sensory conduction of the right peroneal and sural nerves was studied in 28 children (17 HIV seropositive) with inherited hemostasis disorders, without any symptoms of neuropathy. The amplitude ratio of the evoked muscle potential (EMP) at distal stimulation to that at proximal stimulation at the right peroneal nerve was also studied. Thirty healthy aged-matched children were used as controls. There was no statistically significant difference in the distal latency, amplitude and conduction velocity of motor and sensory nerves between patients and controls. On the contrary, a great diminution of amplitude of the EMP during proximal stimulation of nerve was observed in patients, statistically very significant, as compared to controls. This difference was independent of patients' age, severity of hemostasis defect or HIV status. In 9 patients the amplitude was within normal limits. Intraneural oozing due to trivial trauma is postulated as a possible mechanism of peroneal nerve lesion.     

脑白质疏松症患者事件相关电位P300的研究

目的：探讨脑白质疏松症（LA）患者事件相关电位P300成分的特征及与认知障碍的关系。方法：对94例LA患者（其中轻度LA31例,中度LA33例,重度LA30例）和32例正常对照组进行P300检测和简易精神状况检查量表（MMSE）检查。结果：LA患者较对照组MMSE分值降低（P〈0．01）,P300潜伏期延长（P〈0．01）,P300波幅降低（P〈0．05）。轻、中、重度LA患者组间比较MMSE分值降低有差异,P300潜伏期延长有差异（P〈0．01）,但波幅降低有差异仅见于轻、重度LA患者组之间（P〈0．01）。LA组P300潜伏期与MMSE分值间呈负相关（Pz：r=-0．4083,f=4．58,P〈0．01;Cz：r=0．4177．t=4．64,P〈0．01）,P300波幅与MMSE分值间未发现有相关性（P〉0．05）。结论：P300潜伏期可客观评价LA患者的认知功能。     

Characteristics of No-go-P300 component during somatosensory Go/No-go paradigms

The present study investigated one of the characteristics of No-go-related brain activity during somatosensory Go/No-go paradigms, by manipulating the stimulus site and response hand. Somatosensory event-related potentials (ERPs) were recorded in ten right-handed subjects. Electrical stimulation was delivered to the second and fifth digit of one hand, and the subjects had to respond to a Go stimulus by pushing a button with the thumb contralateral to the stimulated side as quickly as possible. We focused on the peak amplitude and latency of Som-Go-P300 (P300 evoked by somatosensory Go stimuli) and Som-No-go-P300 (P300 evoked by somatosensory No-go stimuli) components. The amplitude of Som-No-go-P300, which is very similar to No-go-P300 components following visual and auditory stimulation, was significantly larger than that of Som-Go-P300 at fronto-central electrodes, indicating ‘anteriorization’ of the No-go-P300. The amplitude of Som-No-go-P300 was significantly larger in right than left hemispheres during right hand response conditions, but this difference was not found under left hand conditions. In addition, the difference in amplitude between Som-Go- and Som-No-go-P300, which is frequently described as ‘the Go/No-go effect’ on P300, was significant in the left hemisphere under right hand response conditions, whereas a significant effect was found in both the left and the right hemispheres under left hand response conditions. Our findings suggested that the anteriorization of No-go-P300 was independent of stimulus modalities such as visual, auditory, and somatosensory, and the amplitude of No-go-P300 and Go/No-go effects on P300 was affected by the response hand.     

Influence of skin temperature on latency and amplitude of skin potential responses in the cat

The effect of skin temperature changes on skin potential response (SPR) amplitude and latency was examined in the cat. SPRs were elicited either by stimulating the reticular formation or the distal end of the median nerve. At room temperature, the latency due to the neuroglandular transmission and to the peripheral effector accounts for about half of the total latency of SPR evoked by reticular stimulation. This latency increases to several seconds at low skin temperatures (approximately 10 degrees C), decreases with temperature, and is minimal (300 msec) at high temperatures (over 40 degrees C). SPR amplitude increases with skin temperature, reaches a maximal value (usually around 30 degrees C) and then decreases at higher temperatures. The decrease of latency at higher temperatures confirms results previously obtained in humans. However, the mechanisms of amplitude decrease for high temperatures remain unclear.     

急性河豚中毒患者P300的研究

目的：研究急性河豚中毒患者的P300。方法：应用纽科公司的Medicid-03E脑诱发电位仪测定21例急性河豚中毒患者的视觉（图像）、听觉刺激诱发P300波之潜伏期和波幅,与30例正常对照组作比较,并比较不同病情患者的P300波。对13例患者进行了复测。结果：病人组视觉（图像）、听觉刺激P300波的潜伏期和波幅较正常对照组明显延长（P＜0．001）,波幅明显降低（P＜0．001）。P300波之潜伏期和波幅与患者病情严重程度相关,随着中毒症状的改善,P300波的潜伏期逐渐缩短,波幅也逐渐增高。结论：P300波的变化可作为判断急性河豚中毒患者脑认知功能障碍的程度和恢复情况的一项客观指标。患者P300波的动态观察更有意义。     

六周虚拟现实运动对大学生认知能力影响的事件相关电位测评

评价虚拟现实运动对人体认知能力的影响.随机招募30名健康大学生,实验组(20人)利用爱动运动王Ⅱ进行六周的虚拟现实运动(伸展运动、射箭运动与平衡运动),每次30 min,每周三次.对照组(10人)正常作息.采用德国BP公司生产的32导Brain Vision Analyzer分别测量受试者实验前和六周实验结束后安静状态下的事件相关电位(event-related potential,ERP) P300,选用改良版的Flanker刺激范式.采用SPSS15.0 for windows对数据分别进行描述性统计和推断性统计分析.六周前后组内配对t检验显示,实验组额叶区(F3、F4)和中央区(C3)电极点在一致性刺激时(S1和S2)ERP P300潜伏期较实验前显著延长(P<0.05),额叶区表现更为显著.实验组中顶区(P3)S1刺激下ERP P300波幅较实验前显著增加(P<0.05).对照组和实验组其他电极点和其他刺激方式下未见有显著性改变(P>0.05).六周虚拟现实运动(伸展运动、射箭运动与平衡运动)对大学生认知能力有一定的选择性影响,体现于ERP P300潜伏期和波幅指标显著性改变仅出现在特定的脑区和刺激方式.P300潜伏期改变只出现于额叶区和中央区,P300波幅改变只出现在顶区,且上述改变仅发生在一致性刺激的条件下.这些选择性改变应是对该运动方式的适应性改变.