Semantic and affective processing in psychopaths: an event-related potential (ERP) study.

We tested the hypothesis that psychopathy is associated with abnormal processing of semantic and affective verbal information. In Task 1, a lexical decision task, and in Task 2, a word identification task, participants responded faster to concrete than to abstract words. In Task 2, psychopaths made more errors identifying abstract words than concrete words. In Task 3, a word identification task, participants responded faster to positive than to negative words. In all three tasks, nonpsychopaths showed the expected event-related potential (ERP) differentiation between word stimuli, whereas psychopaths did not. In each task, the ERPs of the psychopaths included a large centrofrontal negative-going wave (N350); this wave was absent or very small in the nonpsychopaths. The interpretation and significance of these differences are discussed.     

The Contingent Negative Variation in Psychopaths

There have been persistent claims that the contingent negative variation (CNV) is absent or greatly attenuated in psychopaths. However, these claims are based on a few studies with serious methodological and diagnostic problems. The present study attempted to avoid these problems. The subjects were male prison inmates divided into psychopaths and nonpsychopaths on the basis of scores on the Psychopathy Checklist. CNV was recorded while the subject performed a forewarned reaction time task with a relatively long interval (6 s) between the warning stimulus and the imperative stimulus. Motivation to perform well was ensured by having reaction times to the imperative stimulus determine how much money would be won or lost on a given trial. The early CNV of psychopaths was significantly larger than was that of the nonpsychopaths. There were no group differences in the late CNV or in reaction time. To the extent that the early CNV reflects processing of the warning stimulus and attention to task demands, the results are consistent with the hypothesis that psychopaths are proficient at focusing attention on events that interest them.     

词汇的概念义和情绪义加工的时间进程研究

目的:对词汇的概念义和情绪义加工的时间进程进行直接的对比研究。方法:以50名健康大学生为被试,采用一种特殊的词汇——双意义情绪词,通过设置不同的SOA条件(50毫秒和300毫秒),同时考察了词汇的语义启动和情绪启动效应,要求被试进行词汇判断任务。结果:在短SOA(50毫秒)条件下,词汇的语义启动效应和情绪启动效应均显著,且两者之间无显著差异;在长SOA(300毫秒)条件下,词汇的语义启动效应显著,但未发现情绪启动效应。结论:词汇概念义的加工同时包括了自动化和控制性的加工过程,而情绪义的加工只包含了自动化的加工过程,表明词汇的概念义和情绪义加工具有不同的时间进程。     

The Processing of Semantic Meaning in Chinese Words and Evoked Brain Topography

The connotative meaning of words can be quantified statistically by the "semantic differential technique" resulting in statistically defined, independent dimensions where every word is uniquely located on the three dimensional evaluation. In an earlier study on German subjects we demonstrated that there are electrophysiological correlates of these meaning dimensions. Here a group of 55 Chinese adults was investigated in two experiments: first, 210 nouns were rated by 32 subjects, and factor analysis on the questionnaire data yielded three independent semantic dimensions. Semantically unique words stemming from these results were then used as stimuli in electrophysiological experiments in another group of 23 healthy right-handed adults. Words of similar physical appearance belonging to different semantic classes were presented visually in random order. The EEG was recorded from 29 channels, and evoked brain activity was computed for each semantic class. Significant differences in electrical brain activation between these semantic word classes were observed as early as 80 ms after stimulus onset, confirming earlier reports on similar findings in German subjects. Further similarities were revealed by a direct comparison of the topographical distribution of potential components elicited by words, and by the results of spatial PCA performed on both sets of data. These results illustrate similar early neural activation based on semantic class, in subject groups of different language and culture.     

The Pharmacology of Human Information Processing

A serial information processing model provides a rough but useful framework for studying effects of age and drugs on human cognition. Using this approach, one varies both the nature of experimental tasks and the biology of the subjects, and one measures both reaction time and event-related potential latencies. For example, we may change a task by varying the complexity of the stimulus or the complexity of the response. We may change the biology of the subject by giving drugs or by using subjects of different ages. The interactions of the independent variables on reaction time and ERP latencies yield convergent data on the properties of information processing stages and on the actions of biological variables upon them. Using this approach we find that methylphenidate acts late on response-related processes while aging acts on earlier and on stimulus-related processes. A review of other studies shows the value of this approach, but is balanced by illustration of some of its problems and shortcomings.     

The Effects of Semantic Priming and Word Repetition on Event-Related Potentials

Event-related potentials (ERPs) were recorded during the performance of a lexical decision task, in which a proportion of the words were either semantic associates or repetitions of the preceding word. Reaction times were faster to both the second member of associated pairs (targets) and repeated words, with the latter facilitatory effect being more than twice that of the former. ERPs to the semantic primes were more negative-going than those to targets. This difference peaked around 400–450 ms after stimulus onset. Comparison of unrepeated and repeated words revealed a larger and temporally more extended difference, with a similar scalp topography. The prime-target differences are interpreted as a further example of the sensitivity of the ‘N400’ component of the ERP to semantic relationships between words. The differences between the repetition and priming effects in ERPs are considered equivocal with respect to the view that the associated behavioural effects are caused by different cognitive mechanisms.     

述情障碍者情绪启动效应的ERPs特征

目的:分析述情障碍者情绪启动中的ERPs特征,探讨述情障碍者情绪自动加工缺陷的神经机制。方法:采用TAS-20中文版筛选出述情障碍者与非述情障碍者进入情绪启动实验。以阈下或阈上方式呈现启动图片,要求受试对目标图片做出正负性的判断,记录受试ERPs数据。结果:在阈上启动任务中,述情障碍组的P2波幅和"启动-非启动"差异波N600波幅均显著小于非述情障碍组的波幅,而阈下启动任务中的P2、P3潜伏期与波幅及N600波幅则均不存在显著组间差异。结论:本研究进一步支持述情障碍者对无意识感知的情绪刺激的自动加工是完整的,而对意识到的情绪刺激的自动加工存在明显的缺陷。     

Does Methylphenidate Affect Information Processing? Findings From Two Studies on Performance and P3b Latency

Two studies were conducted to assess the impact of methylphenidate on normal young adults in a fixed version of Steinberg's memory scanning task. Both studies yielded characteristic monotonic increases in reaction time (RT) and P3b latency as a function of memory load. Also, in both studies, methylphenidate speeded up RT as and decreased error rates and intra subject RT variability. However, the slope of RT as a function of memory load, i.e. the rate of memory search, was not altered by the stimulant. In Study 1, P3b latency also was not affected by methylphenidate, a result suggesting that the stimulant brought about the decrease in RT by acting after the completion of evaluation, presumably by accelerating response processes. However, in Study 2, the drug significantly shortened P3b latency and the interval between RT and P3b latency. Thus, a speeding of both evaluation as well as motor processes was achieved. A review of procedural differences between the two studies suggests some possible explanations. In combination, the two studies indicate that methylphenidate consistently shortened the timing of motor processes and, under some circumstances, the duration of evaluation processes as well.     

Event-related potentials in an auditory semantic oddball task in humans

Whenever rare target stimuli are presented interspersed by frequent irrelevant stimuli (standards), the targets elicit a late parieto-central positive wave called P3. Usually standards and targets differ by a simple physical feature (e.g. tone pitch). Less consistent are the data obtained in semantic tasks, in which standards and targets are represented by different word classes. Given an equal number of words in the target and standard categories, each individual standard is more frequent than each target, that is, the frequency of the category is confounded with that of individual stimuli. In the present study participants were presented five semantic classes each being represented by 15 words. Words belonging to one particular class should be counted. Thus targets were rare (20%), although the frequencies of each word and of each semantic class were equal. A highly significant P3 was recorded. Its latency was longer, and the amplitude was smaller, than when standards and targets were two tones. These data indicate that brain waves recorded in semantic tasks are not necessarily manifestations of specific semantic processing.     

ERP measures of partial semantic knowledge: left temporal indices of skill differences and lexical quality

This study examines the sensitivity of early event-related potentials (ERPs) to degrees of word semantic knowledge. Participants with strong, average, or weak vocabulary skills made speeded lexical decisions to letter strings. To represent the full spectrum of word knowledge among adult native-English speakers, we used rare words that were orthographically matched with more familiar words and with pseudowords. Since the lexical decision could not reliably be made on the basis of word form, subjects were obliged to use semantic knowledge to perform the task. A d' analysis suggested that high-skilled subjects adopted a more conservative strategy in response to rare versus more familiar words. Moreover, the high-skilled participants showed a trend towards an enhanced "N2c" to rare words, and a similar posterior temporal effect reached significance approximately 650 ms. Generators for these effects were localized to left temporal cortex. We discuss implications of these results for word learning and for theories of lexical semantic access.     

Effects of acoustic distortion and semantic context on event-related potentials to spoken words

This study examined the neurophysiological effects of acoustic degradation on auditory semantic processing. Event-related potentials were recorded to target words presented in a sentence context. Targets were semantically congruent or incongruent with the context, which was acoustically intact or low-pass filtered. In unaltered contexts, N400 amplitude was significantly greater for incongruent than congruent words. Filtering significantly reduced this effect, even though participants were highly accurate in interpreting the degraded stimuli, as shown by an anomaly detection task. This reduction in the N400 effect appeared to be driven by decreased N400 amplitudes over posterior electrode sites for incongruent targets. These results demonstrate that acoustic degradation influences the neural response to words in context by reducing the availability of semantic information in on-line sentence comprehension.     

The Processing of Temporal Intervals Reflected by CNV-Like Brain Potentials

The present study employed event-related potentials (ERPs) of the brain to improve the understanding of temporal processing. A reproduction paradigm was realized by presenting a visual stimulus (illuminated screen) for intervals of varying length. A few seconds after presentation of such standard intervals the visual stimulus was switched on again and subjects were asked to reproduce the duration of the standard interval by turning off the illumination after a corresponding interval had elapsed. The length of standard intervals varied randomly with each of the following lengths being presented 20 times: 1, 2, 3, 4, 6, and 8 s. Reproduction was accurate for standard intervals up to 3 s but deteriorated with increasing interval length. Brain potentials during reproduction intervals of 1-3 s differed from those recorded during the longer intervals. A CNV-like slow negative shift developed during the shorter reproduction intervals. Negatively was reduced or even absent, when subjects had to reproduce standard intervals of 4 s or longer. The ERP results suggest that intervals shorter than 3-4 s may evoke a processing mode that is qualitatively different from the one dominating when periods in the range of several seconds have to be processed.     

A single-system account of semantic and lexical deficits in five semantic dementia patients

In semantic dementia (SD), there is a correlation between performance on semantic tasks such as picture naming and lexical tasks such as reading aloud. However, there have been a few case reports of patients with spared reading despite profound semantic impairment. These reports have sparked an ongoing debate about how the brain processes conceptual versus lexical knowledge. One possibility is that there are two functionally distinct systems in the brain—one for semantic and one for lexical processing. Alternatively, there may be a single system involved in both. We present a computational investigation of the role of individual differences in explaining the relationship between naming and reading performance in five SD patients, among whom there are cases of both association and dissociation of deficits. We used a connectionist model where information from different modalities feeds into a single integrative layer. Our simulations successfully produced the overall relationship between reading and naming seen in SD and provided multiple fits for both association and dissociation data, suggesting that a single, cross-modal, integrative system is sufficient for both semantic and lexical tasks and that individual differences among patients are essential in accounting for variability in performance.     

汉语双字词启动任务的事件相关电位时空模式

目的:考察汉语双字词启动任务的事件相关电位(ERP)时空模式特性。方法:以词汇重复(例:大豆-大豆)、语义启动(例:高粱-大豆)和语义失配(例:轮船-大豆)三类关系先后显示启动词和靶词,16名被试判断靶词是否与启动词同类而分别按键,同时记录其行为绩效和19通道ERP,应用单因素三水平重复测量方差分析和配对比较,采用统计参数映像(statistical parametric mapping,SPM)呈现ERP结果。结果:反应时间(F(2,26)=77.28,P=0.00)和正确率(F(2,26)=42.91,P=0.00)的重复启动效应均显著,词汇重复组的行为绩效(反应时间601.44±69.39ms,正确率98.7±1.3%)分别优于语义启动组(774.98±87.34ms,88.2±5.9%)和语义失配组(788.75±88.10ms,87.8±4.8%)。虽然后两组行为绩效差异不显著,但其ERP均可见P200、N400和P600成分。SPM提示额顶颞分布的P200效应(200-250ms)与注意调控相关;中央顶分布的N400效应(300-450ms)与语义加工相关;枕颞分布的P600效应(500-1000ms)可能反映语境重构。结论:双字词启动任务的ERP时空模式反映多层次语言加工功能,适用于语言功能评价。     

Words and sentences: Event-related brain potential measures

Interactions between sentences and the individual words that comprise them are reviewed in studies using the event-related brain potential (ERP). Results suggest that, for ambiguous words preceded by a biasing sentence context, context is used at an early stage to constrain the relevant sense of a word rather than select among multiple active senses. A study comparing associative single-word context and sentence-level context also suggests that sentence context influences the earliest stage of semantic analysis, but that the ability to use sentence context effectively is more demanding of working memory than the ability to use single-word contexts. Another indication that sentence context has a dramatic effect on single-word processing was the observation that high- and low-frequency words elicit different ERPs at the beginnings of sentences but that this effect is suppressed by a meaningful sentence context.     

中文听觉双字词认知中的正字法即时激活效应——来自ERP的证据

目的:探讨中文听觉双字词认知中的正字法即时激活效应.方法:采用事件相关电位(ERP)技术,操纵3种双字词条件(一致性:一致、首字不一致、尾字不一致),选择9个电极,使用时间窗分析技术,以50ms为一个时间窗分析300-350ms以及375-675ms时段的脑电波.结果:对前部脑电波平均波幅进行方差分析发现,三种实验条件在575-625ms时间窗差异显著,而在625-675ms时间窗差异边缘显著.首字不一致和一致条件在575-625ms时间窗差异显著,而在625-675ms时间窗差异边缘显著.结论:在中文听觉双字词认知中可能同样存在正字法即时激活效应.     

Scalp Topography and Intracerebral Sources for ERPs Recorded During Auditory Target Detection

Summary The goal of this study was to measure the scalp topography of the event-related potentials (ERPs) during the detection of improbable auditory targets and to determine the intracerebral sources of these potentials. ERPs were recorded when subjects listened to a sequence of spoken words and detected occasional (p = 0.2) targets defined either by the gender of the speaker (male/female) or the meaning of the word (animate/inanimate). Waveforms were evaluated in relation to category (target versus standard) and task (voice versus semantic). Dipole source analysis was performed using locations obtained from fMRI. Fronto-central negative waves (N450 and N600 ms) generated by sources in both the auditory cortex and frontal regions were larger for semantic tasks and larger over the left hemisphere. A large parieto-occipital positive wave (P700) occurring with a peak latency about 150 ms before the reaction time was mainly generated in the left temporo-parietal regions for the semantic task and bilaterally for the voice task. About 300 ms after the P700, a highly lateralized right temporo-parietal positive wave P1000r occurred with a source in the right temporo-parietal area. These results indicate three distinct physiological processes underlie the detection of auditory targets. Perceptual discrimination is related to interactions between the frontal and temporal regions, stimulus-response association occurs in the temporo-parietal regions and post-perceptual processing in the right temporo-parietal region.     

Event-Related Potentials and Recognition Memory For Pictures and Words: The Effects of Intentional and Incidental Learning

Event-related potentials were recorded under conditions of intentional or incidental learning of pictures and words, and during the subsequent recognition memory test for these stimuli. Intentionally learned pictures were remembered better than incidentally learned pictures and intentionally learned words, which, in turn, were remembered better than incidentally learned words. In comparison to pictures that were ignored, the pictures that were attended were characterized by greater positive amplitude frontally at 250 ms and centro-parietally at 350 ms and by greater negativity at 450 ms at parietal and occipital sites. There were no effects of attention on the waveforms elicited by words. These results support the view that processing becomes automatic for words, whereas the processing of pictures involves additional effort or allocation of attentional resources. The N450 amplitude was greater for words than for pictures during both acquisition (intentional items) and recognition phases (hit and correct rejection categories for intentional items, hit category for incidental items). Because pictures are better remembered than words, the greater late positive wave (600 ms) elicited by the pictures than the words during the acquisition phase is also consistent with the association between P300 and better memory that has been reported.     

Ambiguous words in sentences: brain indices for native and non-native disambiguation

In the present study, we compare how native speakers and second language learners process homonyms (such as bank and jam) in sentence context during a late processing phase that involves selection of the appropriate meaning. With both participant groups, we conducted a combined reaction time (RT)/event-related brain potential (ERP) lexical decision experiment with a long stimulus-onset asynchrony (SOA) of 800 ms. Related primes were homonyms at the end of sentences with a context biasing one of the homonym meanings, and targets reflected the contextually appropriate or inappropriate meaning. Both RT and ERP semantic priming in the N400 component revealed that for both natives and learners, only contextually appropriate meanings were primed, or still active, late in processing. The results indicate that L2 learners show similar, though slower, homonym processing mechanisms to those of native speakers of a language, and that both groups can achieve disambiguation based on semantic context.     

Neurophysiological measures of reading difficulty in very-low-birthweight children

Twenty-four 8-10-year-old children (13 very low birthweight, 11 control) performed a lexical decision and a semantic classification task while event-related potentials (ERPs) were recorded. Both groups were within normal range on standardized reading tests, but the very-low-birthweight group had lower scores. There were no differences between groups in reaction times or accuracy for ERP tasks. On analyses of P2a (246 ms anteriorly), P2p (336 ms posteriorly), N2a (356 ms anteriorly), and N2p (396 ms posteriorly) peaks and a late positive component, control children showed greater right than left asymmetry at P2p and greater left than right asymmetry at N2a. Very-low-birthweight children showed less asymmetry. For the late positive component, both groups showed greater left than right asymmetry, which was more marked for the semantic classification task. The results suggest that very-low-birthweight children display differing cortical utilization during reading.