Neuroelectric assessment of HIV: EEG, ERP, and viral load.

The effects of the human immunodeficiency virus (HIV) infection on the central nervous system function were studied with electroencephalographic (EEG) and auditory event-related brain potentials (EPRs) in patients infected with HIV and unaffected young adult control subjects (n=10/group). All subjects were assessed once every 15 min for four trial blocks at the same time of day to assess EEG/ERP changes with time on task-induced fatigue. Spectral analysis was applied to the pre- and post-stimulus EEG segments. ERP values were evaluated with respect to group differences for component amplitude and latency measures. Spectral analysis demonstrated that HIV patients evinced greater pre-stimulus delta power over frontal areas compared to control subjects, and less post-stimulus spectral power for the delta, theta, and alpha bands over the central/parietal areas. P300 amplitude was smaller, and latency was marginally longer for the HIV patients compared to control subjects. P300 latency correlated positively with increases in the patient HIV viral load. Time-on-task generally did not affect EEG or ERP measures for either group other than contributing to an overall decrease in neuroelectric responsivity. Group spectral power effects were consistent with differences in arousal/fatigue level. P300 group differences were consistent with declines in cognitive capability, and P300 latency increased with increased viral load. HIV infection negatively affected central nervous system function as measured by EEG and cognitive ERPs in a manner that suggests decreased arousal and increased fatigue in HIV patients.     

The P300 component in sleep

The present investigation utilized the P300 component of the auditory evoked potential as an index of information processing (discrimination) in sleep. Auditory evoked potentials were recorded to target and nontarget stimuli during sleep stages 3/4, 2 and REM under two probability conditions. Corresponding "nontone" waveforms were generated in each sleep stage, representing averaged EEG activity with no tones presented. Target P300 amplitude was higher than both corresponding "nontone" targets and tone nontargets. Probability did not affect the target-nontarget relationship. Latency of P300 increased and amplitude decreased from wakefulness through sleep; however, neither amplitude nor latency differed among sleep stages. Amplitude and latency of N200 increased during sleep. While N200 amplitude was highest in Stage 3-4, N200 latency did not differ among sleep stages. These findings suggest that the P300 recorded in sleep indexes similar cognitive processes as the P300 recorded in wakefulness. That P300 as well as N200 latency increased in sleep suggests that processes indexed by these components may slow during sleep.     

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.     

P300 amplitude age reductions are not caused by latency jitter

Studies of the event-related potentials (ERPs) P3a/P3b have given insights into age effects on cognitive processes in the brain, and it has been established that latency increases and amplitude decreases with age. However, if latency jitter, that is, variation in single trial latencies, is larger in elderly than in younger participants, this may create an artificial age-amplitude correlation. The aim of this article is to test whether correction for latency jitter affects the P3a/P3b age correlations. One hundred thirty-three healthy adults (20-88 years old) went through a 3-stimuli visual oddball paradigm. Latency jitter was corrected by use of a Maximum Likelihood Estimation method. The results showed that corrections for latency jitter did not significantly affect the correlations between P3a/P3b and age. It is concluded that previous reports of amplitude reduction as a function of age seem to be valid regardless of whether latency jitter correction has been applied.     

Comparison of P300 from a Passive Tone Sequence Paradigm and an Active Discrimination Task

The P300 (P3) event-related potential elicited with a passive tone sequence paradigm was compared with an active auditory discrimination task. Each stimulus situation was replicated successively to study repetition effects. The first stimulus of the tone sequences produced a positive-going potential with a scalp distribution and peak latency similar to the P3 from the active discrimination task, although its amplitude was smaller than that obtained from the active paradigm. The first block of trials demonstrated the strongest correlations for both P3 latency and amplitude between the sequence and discrimination tasks. The results suggest that the passive tone sequence paradigm may provide P3 measures which approximate those acquired from an active discrimination task.     

The Influence of Unequal Numbers of Trials on Comparisons of Average Event-Related Potentials

Four studies examined (a) how event-related potentials (ERPs) change as the number of trials averaged increases and (b) the statistical implications of comparing ERPs composed of different numbers of trials. Experiment 1 utilized data from 7-year-old children performing an oddball task. The other three experiments used simulated data with different distributions of P3 peak latency. In all 4 experiments, peak amplitude decreased and the mean amplitude of the 300 to 900 msec interval remained stable as the number of trials averaged increased. The standard deviations of both measures decreased. These data show that the decrease in peak amplitude with increasing numbers of trials that has been found in other studies is not solely due to the elimination of residual noise but is likely to also involve a fundamental aspect of signal averaging and the algorithm used to select peaks. Furthermore, these experiments expose the possibility of statistical errors when investigators compare average ERPs composed of small versus large numbers of trials as is often done when the oddball paradigm is used.     

Electrocortical correlates of intra-subject variability in reaction times: average and single-trial analyses

Intra-subject variability of reaction times (ISV), generally considered secondary to measures of central tendency, has become increasingly important for cognitive neuroscience. Event-related potential (ERP) research suggests an inverse relationship between ISV and P3b amplitude; however ERP methods’ reliance on averaged waveforms may be unsuitable for studying ISV due to potentially distorting effects of latency jitter. The present study investigates the neural bases of ISV through single-trial analysis of P3bs in groups with low and high ISV, using Infomax-rotated principal components analysis of ERP data. Results indicate that while latency jitter contributes to the reduced P3b amplitude seen in average ERPs of high ISV participants, group differences in amplitude survive the use of single-trial methods that are robust to such distortions. A decoupling of P3b and RT was also seen in the high ISV group. The results are discussed in the context of the P3b's dimensionality, and its possible catecholaminergic underpinnings.     

The influence of unequal numbers of trials on comparisons of average event-related potentials

Four studies examined (a) how event-related potentials (ERPs) change as the number of trials averaged increases and (b) the statistical implications of comparing ERPs composed of different numbers of trials. Experiment 1 utilized data from 7-year-old children performing an oddball task. The other three experiments used simulated data with different distributions of P3 peak latency. In all 4 experiments, peak amplitude decreased and the mean amplitude of the 300 to 900 msec interval remained stable as the number of trials averaged increased. The standard deviations of both measures decreased. These data show that the decrease in peak amplitude with increasing numbers of trials that has been found in other studies is not solely due to the elimination of residual noise but is likely to also involve a fundamental aspect of signal averaging and the algorithm used to select peaks. Furthermore, these experiments expose the possibility of statistical errors when investigators compare average ERPs composed of small versus large numbers of trials as is often done when the oddball paradigm is used.     

Reduction in event-related alpha attenuation during performance of an auditory oddball task in schizophrenia.

EEG frequency-domain analyses have demonstrated that cognitive performance produces a reduction in alpha activity, i.e., alpha attenuation, such as event-related desynchronization (ERD), reflecting brain activation. To examine whether schizophrenic patients have abnormalities in frequency-domain, event-related alpha attenuation, as well as in time-domain EEG phenomena, such as event-related potential, we compared alpha power change and P300 elicited simultaneously in response to the presentation of target tones in an auditory oddball paradigm between patients with schizophrenia and normal control subjects. In both patients and controls, alpha power was smaller during the time window of 512 ms following targets than following non-targets, particularly at the parietal and the posterior temporal locations (Pz, T5, and T6). The size of alpha attenuation measured as percent reduction in alpha power produced by targets relative to non-targets was smaller in patients than in controls at the posterior temporal locations. The size of alpha attenuation showed no correlation with P300 amplitude or latency in either patients or controls. Furthermore, in patients, the size of alpha attenuation showed no correlation with symptom severity, while P300 amplitude was correlated negatively with the positive subscale score of the Positive and Negative Syndrome Scale. These findings suggest that the symptom-independent reduction in event-related alpha attenuation in schizophrenia may be useful as an electrophysiological index of the impairment of neural processes distinct from that indexed by symptom-dependent P300 abnormalities.     

性别因素对老年期神经系统变性过程的影响

目的：研究探讨正常人进入老年期后，性别和年龄对事件相关电位的交互作用影响是否仍然持续。方法：应用神经心理学测试和MRI检查筛选日本冲绳县年龄在60岁以上的正常老年人40名。其中男性17名，平均年龄是72．2±8．6岁；女性23名，平均年龄是75．7±8．2岁。应用听觉“oddball”范式诱发事件相关电位P300。分析Fz和Pz部位记录到的事件相关电位内源性成分P300和N2b。结果：P300潜伏期、P300波幅和N2b潜伏期的组间差异不显著。于Fz部位，男性组的N2b波幅低于女性组（F=4．59，P=0．039）。P300潜伏期和P300波幅与年龄的相关性，仅见于男性组（Fz-P300潜伏期：r=0．584，P=0．014；Fz-P300波幅：r=-0．782，P〈0．001；Pz—P300潜伏期：r=0．587，P=0．013；Pz—P300波幅：r=-0．657，P=0．004）。P300潜伏期和P300波幅对年龄的线性回归坡度，在两组闾均有显著性差异，在男性组更为陡峭（Fz—P300潜伏期：t=2．11，P=0．042；Fz-P300波幅：t=2．55，P=0．015；Pz-P300潜伏期：t：2．70，P=0．011：Pz-P300波幅：t=3．00，P=0．005）。结论：性别因素对老年期神经系统变性过程有显著影响。     

基于自适应动态特征库的P300诱发脑电单次提取算法研究

目的 诱发电位的单次提取技术一直是脑电信息处理领域的难题之一,为进一步提高单次提取算法的时间准确性和特征精度,针对体感诱发脑电数据信噪比低、试次间参数变化大的特点,研究诱发脑电参数单次提取新算法,保留试次间诱发脑电的动态特性,并提高估计准确率.方法 基于小波滤波和多元线性分析技术,加入自适应动态特征库并由此提出的诱发脑电P300参数单次提取新方法.随机选取4组小波滤波(WF)后诱发脑电数据,分别叠加平均后进行主成分分析(PCA)组成特征库.单次提取时,针对每试次数据从特征库中选择与当次诱发脑电信号相关系数最高的成分作为自变量开展多元线性回归分析,由回归分析结构重构出单次诱发电位信号并自动提取潜伏期和幅值等关键特征.结果 与专家判定的基准数值相比,新算法预测的P300成分潜伏期与幅值参数更准确,两者的平均差值分别为(11.16±8.60) ms和(1.40±1.34)μV;与常用的叠加平均法结果亦更为接近,平均差值分别为(23.26±25.76) ms和(2.52±2.50) μV,新算法相比传统多元线性回归分析算法具有显著优势.结论 将动态更新的诱发脑电数据主成分样本库应用于小波滤波与多元线性回归方法,能有效保留单次诱发脑电数据中的动态特征,从而提升参数估计的准确率.     

脑电图和事件相关电位在精神分裂症 认知功能评估中的应用

探讨脑电图（EEG）和事件相关电位（ERP）检查在精神分裂症患者认知功能评估中的应用价值。方法 选取 2013年5月~2018年5月本院住院缓解期精神分裂症患者68例,对患者进行蒙特利尔认知评估量表（MoCA）、EEG和MMN检查,分析EEG改变特点,根据EEG结果分为EEG正常患者、癫痫样放电患者、慢波性异常患者,根据MoCA和事件相关电位变化特点评估患者认知功能并比较其差异,同时根据病程分析EEG和事件相关电位的变化并比较其差异。结果 ERP正常患者、癫痫样放电患者、慢波性异常患者认知障碍比较,差异有统计学意义（P＜0.05）;随着病程的延长,δ波、θ波平均功率逐渐增高,差异有统计学意义（P＜0.05）;事件相关电位MMN、P300潜伏期延长和波幅降低随着精神分裂症患者病程的延长而变化,差异有统计学意义（P＜0.05）;但长期患者潜伏期保持稳定（P＞0.05）。结论 在精神分裂症诊断中应用脑电图和事件相关电位检查,能够有效评估认知功能减退,对控制病情、药物选择及判断预后具有重要意义。     

P3 and delta band responses in visual oddball paradigm in schizophrenia

Amplitude reduction of the oddball P3 wave is a well-replicated but non-specific finding of schizophrenia. The time-frequency analysis of single-trial ERP data allows to specify in a reliable manner whether the P3 reduction in schizophrenia is due to the decreased P3 response in single trials or due to the inter-trial variability in the timing of the response. Since the delta response most strongly contributes to the P3 amplitude, we focused to the low frequency range of the time-frequency transformed data. EEG was recorded from chronic schizophrenia patients and matched healthy controls during a simple visual oddball task. The wavelet transforms of the averaged ERP and the single trials were computed to investigate the amplitudes of the evoked (phase-locked) and total (phase-locked+non-phase-locked) delta (1-3 Hz) responses, respectively. Evoked delta activity and P3 amplitude to target stimuli were both reduced significantly in patients with schizophrenia, whereas no such difference was obtained for the total delta activity. The significant reduction of the evoked delta response and the absence of such a difference in the total delta response of schizophrenia patients reveals that the delta band response is weakly phase-locked to stimulus in schizophrenia. This result suggests that the reduced P3 amplitudes in the averaged ERPs of schizophrenia patients result from a temporal jitter in the activation of neural circuits engaged in P3 generation.     

Genetic overlap between P300, P50, and duration mismatch negativity.

Mismatch Negativity (MMN), P300, and P50 suppression event-related potential (ERP) components measure intermediate stages of information processing but little is known of how they relate to each other genetically. The present study used multivariate genetic model fitting analytic techniques in 46 monozygotic and 32 dizygotic twin pairs. P300, P50 suppression, and MMN were recorded using a 19-channel electroencephalograph (EEG). Zygosity was determined using DNA genotyping. Little evidence for either genetic or environmental association between each of the three ERP paradigms was found. This result suggests that P300, MMN, and P50 suppression serve to evaluate different brain information processing functions that may be mediated by distinct neurobiological mechanisms which in turn are influenced by different sets of genes. Within paradigm, P300 amplitude and latency shared about half of their genetic effects.     

癫患者的事件相关电位与认知功能研究

目的 :探讨癫患者事件相关电位 (ERP)与认知功能状况。方法 :对 35 0例癫患者和15 0例正常对照组进行认知功能 30题 (CCSE)、简易智力状态试验 (MMSE)和ERPP30 0 的测定。结果 :癫部分性发作者的P30 0 潜伏期比全身性发作者明显延长 ,波幅降低显著 ,认知功能测试得分也较低 ;未能分类发作患者的P30 0 潜伏期延长不明显 ,认知功能测试得分近于正常。病程 >5年者的P30 0 潜伏期较病程 1～ 5年的延长明显 ,波幅降低显著 ,认知功能测试得分也较低 ;病程 <1年者P30 0 潜伏期延长不明显 ,认知功能测试得分在正常范围。同时用三种药者的P30 0 潜伏期较同时用两种药者的延长明显 ,波幅降低显著 ,认知功能测试得分也较低 ;同时用两种药者的P30 0 潜伏期也比用一种药者明显延长 ,认知功能测试得分也较低 ;用一种药者的P30 0 潜伏期延长不明显 ,认知功能测试得分在正常范围。结论 :部分性发作患者的P30 0 潜伏期延长较全身性发作者明显 ;病程越长 ,P30 0 潜伏期延长越显著 ;多种用药患者的P30 0 潜伏期延长较用一种药者显著。     

Influence of task difficulty on the features of event-related potential during visual oddball task

We present a comprehensive analysis of the change in event-related potential (ERP) due to task difficulty during a visual oddball task. Specifically, we investigated the inter-subject difference in difficulty-related change of ERP patterns using single-trial ERP analysis focusing on P300 and P2 components. ERPs were recorded and analyzed from 14 subjects while performing a visual oddball task with two difficulty levels. After extracting independent components (ICs) from single-trial ERPs, the averaged ERPs were used to identify which ICs originated from major ERP components. The ERP components were estimated from single-trial waveforms by back-projecting relevant ICs onto scalp electrodes after removing all other ICs; thus, the comparison of ERP components could be performed for each subject. The averaged P300 amplitude was smaller and latency was larger for the more difficult task, and this tendency was also observed for single-trial ERP analysis within each subject. P2 amplitude increased for the hard task for both group and individual analyses, suggesting that the P2 may be interpreted as a manifestation of task relevance evaluation or response generation. The P2 amplitude and latency were more notably correlated with response time for the more difficult task.     

酒依赖患者及其一级亲属听觉ERP研究

目的：对酒依赖患者及其一级亲属（父母、同胞或子女）组与正常对照组的听觉事件相关电位（ERP）进行对照研究,以了解酒依赖患者认知功能状况及酒依赖的遗传易感性。方法：收集40例男性酒依赖患者以及40例一级亲属和40例健康对照者进行听觉ERP检测。结果：酒依赖组和亲属组ERP的P3波（P300成分）波幅均明显低于对照组（均为P〈0．05）;而P3波幅在患者组和亲属组之间比较差异无显著意义（P〉0．05）;酒依赖组N2、P3潜伏期延长（P〈0．01）,而N2、P3潜伏期在亲属组和对照组之间的比较差异则无显著意义（P〉0．05）。结论：ERP反映酒依赖认知功能损害,可以作为酒依赖认知功能损害评估的重要检测手段之一;P3波幅可能是酒依赖的遗传易感性标志,可以作为预测酗酒的指标;对酒依赖一级亲属进行听觉ERP检测可早期发现高危人群,及时提供干预措施。     

The Wisconsin Card Sort Test and P300 responses to novel auditory stimuli in schizophrenic patients

The authors studied the relationship between performance on the Wisconsin Card Sort Test (WCST) and P300 activity in schizophrenics and normal controls. Fourteen male predominantly medicated schizophrenics and matched non-ill controls were administered the WCST and tests of temporal lobe (delayed verbal and spatial memory) and general intellectual functioning (Shipley). Patients were rated with negative and positive symptom scales extracted from the Brief Psychiatric Rating Scale. Subjects performed a tone discrimination task requiring identification of rare targets in both a standard oddball paradigm and a three-stimulus paradigm that included rare novel sounds. Reference independent data from 16 scalp electrodes yielded Global Field Power (GFP), from which P300 latency was determined. P300 amplitude measures included amplitude at this identified latency as well as amplitude integrated over a 100 ms time window centered over it. These amplitude measures were examined at six selected electrode locations. Schizophrenics produced smaller P300 responses that tended to be slower, but there were no group differences in the relationships between neuropsychological performance and P300 responses. Across diagnostic groups percent perseverative errors predicted lower integrated and peak P300 amplitude during the novel but not the standard oddball paradigm. The effect on integrated P300 amplitude was localized to anterior leads after novel stimuli. Negative symptoms predicted lower WCST performance, lower integrated P300 amplitude, and smaller GFP after novel stimuli. Positive symptoms predicted reduced overall GFP and specific but inconsistent reductions in parietal P300 amplitude. The results suggest relationships between dorsolateral prefrontal competence, P300 activity in response to stimulus novelty, and negative symptoms in schizophrenic patients, paralleling findings obtained from blood flow and other measures of brain activity.     

Heritability and Reliability of P300, P50 and Duration Mismatch Negativity

Background Event-related potentials (ERPs) have been suggested as possible endophenotypes of schizophrenia. We investigated the test–retest reliabilities and heritabilities of three ERP components in healthy monozygotic and dizygotic twin pairs.Methods ERP components (P300, P50 and MMN) were recorded using a 19-channel electroencephalogram (EEG) in 40 healthy monozygotic twin pairs, 19 of them on two separate occasions, and 30 dizygotic twin pairs. Zygosity was determined using DNA genotyping.Results High reliabilities were found for the P300 amplitude and its latency, MMN amplitude, and P50 suppression ratio components. Intra-class correlation (ICC) = 0.86 and 0.88 for the P300 amplitude and P300 latency respectively. Reliability of MMN peak amplitude and mean amplitude were 0.67 and 0.66 respectively. P50 T/C ratio reliability was 0.66. Model fitting analyses indicated a substantial heritability or familial component of variance for these ERP measures. Heritability estimates were 63 and 68% for MMN peak amplitude and mean amplitude respectively. For P50 T/C ratio, 68% heritability was estimated. P300 amplitude heritability was estimated at 69%, and while a significant familiality effect was found for P300 latency there was insufficient power to distinguish between shared environment and genetic factors.Conclusions The high reliability and heritability of the P300 amplitude, MMN amplitude, and P50 suppression ratio components supports their use as candidate endophenotypes for psychiatric research.Edited by Wendy SlutskeThis study was supported by British Academy grant SG-36241 to UE and the Stanley Medical Research Institute. Mei Hua Hall is awarded the Taiwanese scholarship at King’s College London. Katja Schulze is supported by a Guy’s & St Thomas’ Charitable Foundation Research Studentship. Elvira Bramon and Marco Picchioni are Wellcome Trust fellows.     

Changes in P300 latency and amplitude in schizophrenic patients and healthy controls during the examination.

In 30 schizophrenic patients (sixteen of the paranoid subtype, 14 of the nonparanoid) and healthy controls (n = 30) event-related potentials were obtained with a somatosensory reaction-time (RT) version of the "oddball paradigm" by stimulating the right (first run) and the left (second run) median nerve. Variations of P300 amplitude and latency and of RT within the average (30 trials) were studied by fractionating off-line the original averages in three subaverages. After stimulation of the right median nerve oscillations on P300 amplitude and latency were observed. After stimulation of the left median nerve there was a trend toward a decrease of the P300 amplitude that reached significance at the electrode P3 for patients (p = 0.014) and at the electrode P4 for controls (p = 0.025). The P300 latency showed variations for patients and controls. The mean-RT was prolonged across the subaverages only for schizophrenics, reaching significance after stimulation of the right median nerve. Paranoid and nonparanoid schizophrenic patients showed similar results on P300 and RT parameters across the subaverages. These results are discussed in terms of the influence of motivation and task involvement on the P300 amplitude. These could be unspecific factors that account for the habituation of the P300 along the examination.