The N400 component of event-related potentials in schizophrenic patients: a preliminary study.

ERPs were recorded during a word recognition task to investigate cognitive dysfunction in schizophrenia. Thirteen medicated schizophrenics and 26 normal controls were tested. In each trial a pair of stimuli, S1 (a word) and S2 (a word or a non-word), were presented. The subjects were required to discriminate between a word and a non-word for S2 (lexical decision task). In a related (R) condition, S2 was the antonym of S1 (e.g., brother-sister); in an unrelated (U) condition, S1 and S2 were semantically unrelated (e.g., brother-drive); in the non-word (N) condition, S2 was a non-word (e.g., brother-grofe). The ERPs for S2 were analyzed, and the contextual effects on the ERPs for S2 observed for both the patients and controls. For both groups, in the U and N conditions S2 elicited a large negative-trending deflection (N370). In contrast, in the R condition it elicited only a small negative-trending notch. There was no difference in the amplitude of N370 between the groups, but its latency was more prolonged or its wave shape more extended for the schizophrenics than for the controls. The N400 amplitude is concluded to remain unchanged in schizophrenics.     

精神分裂症患者视觉P300检查与随访

目的：探讨精神分裂症患者Ｐ３异常的意义,以及抗精神病药物可能的影响。方法：对２１例精神分裂症患者在发病期及２年缓解期后采用视觉图像辨认作业引出ＣＺ点Ｐ３００进行研究。结果：病例组发病期与缓解期均有Ｐ３潜伏期延长与波幅下降,较正常对照组统计学意义。结论：Ｐ３可作为一种潜在的认知功能评价工具,应用于精神病学研究。     

Effects of risperidone on event-related potentials in schizophrenic patients

In order to examine the effects of risperidone on cognitive impairment in schizophrenia, event-related potentials (ERPs) were recorded before and after switching from conventional neuroleptics to risperidone in schizophrenic patients. ERPs were recorded during two auditory discrimination tasks (an oddball task and a distraction task) in 10 medicated schizophrenic patients during conventional neuroleptic and risperidone treatments. The amplitudes and latencies of N 100 and P300 component were measured in ERPs for target stimuli in the oddball task and in ERPs for target and novel stimuli in the distraction task. Although N 100 amplitude and latency and P 300 amplitude did not change significantly after switching the drug compared to that during conventional neuroleptic treatment, P 300 latency for target stimuli shortened significantly during risperidone treatment in both tasks, accompanied by the shortening of the reaction time in the distraction task. The P 300 latency change did not correlate with the change of the severity of psychopathology. These findings suggest that risperidone may speed the information processing in schizophrenic patients, contributing to the improvement of cognitive functions.     

Matching faces for semantic information and names: an event-related brain potentials study

In face identification, it has been controversial whether or not access to biographical information and to a person's name are mediated by qualitatively different loci. We recorded ERPs while participants saw two successive faces and performed a matching task that either required retrieval of semantic information ("same or different profession?"), or retrieval of the person's name ("same or different number of forename syllables?"). For both tasks, slow ERP activity between the first and the second face was characterized by a prominent right posterior negativity, with the asymmetry being larger for the name than the semantic matching task. ERPs to the second face showed a difference between congruent (matching) and incongruent (mismatching) trials, with more negative ERPs for incongruent trials. In the semantic matching task, these differences were significant between 450 and 550 ms, and resembled an N400, with a maximum negativity over the vertex. In the name matching task, the topography of this congruency effect was qualitatively different from that seen in semantic matching. These findings suggest that different brain substrates mediate the access to semantic and name information.     

Brain error-monitoring activity is affected by semantic relatedness: an event-related brain potentials study

Speakers continuously monitor what they say. Sometimes, self-monitoring malfunctions and errors pass undetected and uncorrected. In the field of action monitoring, an event-related brain potential, the error-related negativity (ERN), is associated with error processing. The present study relates the ERN to verbal self-monitoring and investigates how the ERN is affected by auditory distractors during verbal monitoring. We found that the ERN was largest following errors that occurred after semantically related distractors had been presented, as compared to semantically unrelated ones. This result demonstrates that the ERN is sensitive not only to response conflict resulting from the incompatibility of motor responses but also to more abstract lexical retrieval conflict resulting from activation of multiple lexical entries. This, in turn, suggests that the functioning of the verbal self-monitoring system during speaking is comparable to other performance monitoring, such as action monitoring.     

The P300 component of event-related potentials in schizophrenic patients

In a pilot study, the P300 component of the ERP subsequent to competitive visual stimulation was examined in 12 schizophrenic patients (paranoid hallucinatory schizophrenia in partial remission, neuroleptic medication). In the competitive stimulation with a varying information content of the non-target stimuli, healthy probands showed a distinct increase in the amplitude of the P300 components according to a in the frequency of the non-target stimuli. The P300 components during these changing stimulatory conditions remained constant in the schizophrenic patients. This reduction in the reactivity of the P300 component subsequent to an increasing information content of the non-target stimuli can be interpreted as a disturbance in the selective information processing. The ability to adequately react to the information content of irrelevant stimuli appears to be reduced in the schizophrenic patients we examined.     

Facial affect decoding in schizophrenic disorders: a study using event-related potentials

Deficits in emotional processing are evident in schizophrenia, but the underlying processes are still under debate. In this study we tried to replicate findings of diminished prefrontal electroencephalographic response during facial affect recognition in healthy controls and subsequently in schizophrenic patients. As a first step, we analysed the event-related potentials (ERPs) of 36 healthy subjects during emotional expression decoding compared with neutral face viewing. Subsequently, the ERPs of 22 patients with schizophrenia were compared with the ERPs of 22 healthy subjects matched for age and sex. The hypothesised increase in the negative component at 200 ms over frontal brain regions during facial affect decoding was not found in this study. Instead we found increased positive amplitudes at 300 ms over parietal brain areas for the active affect-decoding task compared with the passive neutral face-viewing task. Interestingly, schizophrenic patients had higher amplitudes in the neutral condition than did healthy controls. This effect was more pronounced in the paranoid subgroup of patients.     

Early visual components (P100, N170) are disrupted in chronic schizophrenic patients: an event-related potentials study.

INTRODUCTION: On the basis of the Positive and Negative Syndrome Scale (PANSS), fourteen schizophrenic patients and 7 normal controls were confronted with pictures from the Ekman & Friesen series in an event-related potentials study. PROCEDURE: Participants were confronted with a visual face-detection task, in which they had to detect, as quickly as possible, deviant faces amongst a train of standard stimuli (neutral faces). Deviant faces changed either on identity (different identity, neutral expression), or on emotion (same identity, happy, fearful or sad expression). RESULTS: Schizophrenics exhibited a decrease in amplitude of the face N170, recorded around 170 ms at occipito-temporal sites; this was observed as well for emotional as for identity faces, which suggests a global involvement of face processing. Moreover, this decrease of the face-N170 was positively correlated to positive, but not negative, symptoms of schizophrenia. Finally, the amplitude of P100 was also decreased, which suggests that the N170 decrement would result from a more global deficit in visual processing deficit. DISCUSSION: It is suggested that, in schizophrenics, an involvement of early visual processing might underlie the decreased amplitudes and the higher onset latencies of later P300 and N400 components.     

精神分裂症患者事件相关电位药物治疗前后对照研究

目的 探索精神分裂症事件相关电位（ERPs）特征及非典型抗精神病药物治疗对其的影响。方法 22例从未用过抗精神病药或停药两周以上的精神分裂症患者以及15例健康受试者进行ERPs检查。然后22例患者分别给予利培酮或氯氮平治疗6周，观察治疗后患者ERPs的变化经情况。结果 与正常受试者比较，治疗前精神分裂症患者表现P3波幅降低，治疗后P3幅值降低得到改善。利培酮治疗可明显增加P3幅值，氯氮平治疗P3幅值增加较少。结论 精神分裂症患者ERPs异常主要表现P3幅值降低，利培酮治疗可显著改善这种异常。     

Differences between noun and verb processing in a minimal phrase context: a semantic priming study using event-related brain potentials

The aim of the present study was to enforce the priming of either nouns or verbs in order to evoke word-category-specific N400 effects. In two experiments two primes which were either a verb-noun or a noun-noun pair were followed by a semantically related or unrelated target which was a noun or verb, respectively. This target always completed the word sequence to a minimal phrase comprising verb, subject, and object (VNN or NNV triplets). In experiment I subjects judged the semantic relatedness of the target to the two primes, in experiment II subjects first generated an appropriate target of the required word category and then judged the semantic relatedness between self-generated word and target. ERPs were recorded from 124 scalp electrodes. In both experiments verbs and nouns as such evoked reliably distinct ERP topographies between 300 and 800 ms. With verbs in relation to nouns the amplitudes were most often found to be more positive over central to frontal or parietal areas and more negative over occipital and temporo-parietal areas. In contrast, N400 effects proved as topographically invariant for noun and verb targets in both experiments. The results suggest that access to noun and verb representations involves topographically distinct cell assemblies while the N400 effect seems to reflect semantic evaluation and integration processes which are more abstract and independent from a particular word category.     

Parametric analysis of event-related potentials in semantic comprehension: evidence for parallel brain mechanisms

In event-related potential (ERP) studies of cognitive processes, the electrophysiological responses are typically contrasted between experimental conditions that are taken to represent discrete categories (e.g. attended vs. unattended stimuli, or real vs. nonsense words). Because categorical variation is less powerful than continuous or parametric variation, a more effective method may be to relate continuous variation in the cognitive process with matching variation in the electrophysiological responses. We assessed continuous variation in the expectancy and meaningfulness of words in different sentence contexts by having subjects rate the words along these two dimensions. ERP averages were then created for each word by averaging the ERP across all subjects' responses to that word. A parametric principal components analysis was then conducted by multiplying the factor topographies from the temporal PCA by the parameter correlation maps for each rating parameter. This analysis showed that both expectancy and meaningfulness begin to influence lexical processing around 200 ms. Source localization of the expectancy N2 (recognition potential) pointed to a source in the left fusiform gyrus region (visual word form area). Source localization of the meaningfulness N2 (meaning recognition potential) suggested a right inferior posterior source, such as in the right cerebellum or right fusiform area. Further research with parametric analysis of dense array ERPs may clarify the multiple neural mechanisms of word recognition.     

Working memory deficit in patients with restless legs syndrome: an event-related potential study

ObjectiveThe aim of this study was to investigate whether there is a working memory (WM) deficit in restless legs syndrome (RLS) patients, by studying the Sternberg WM task of event-related potential (ERP).MethodsThirteen drug-naive RLS patients and 13 healthy age-matched controls with no sleep disturbances participated in the present study. P300 ERP was recorded during Sternberg WM task using digits as mnemonic items. P300 amplitudes and reaction times were compared between groups (RLS vs control) considering brain regions (frontal, central, and parietal) and memory load sizes (two, three, and four) as within-subject factors. Clinical and sleep-related variables were correlated with P300 amplitude.ResultsThe reaction time in RLS patients was significantly longer than controls over all memory load sizes. The P300 amplitude at parietal regions in RLS patients was significantly lower than in controls regardless of memory load sizes, which was significantly negatively correlated with duration of RLS history in RLS patients.ConclusionOur study suggests that patients with severe RLS have WM deficits. Furthermore, negative correlation of P300 amplitudes with the duration of RLS illness suggests that cerebral cortical dysfunction in RLS patients results from repeated RLS symptom attacks.     

Automatic activation of the semantic network in schizophrenia: evidence from event-related brain potentials.

BACKGROUND: Language disorder associated with schizophrenia might be due to disturbances in both automatic activation and mechanisms of controlled attention. The contribution of each process to semantic memory dysfunction has not been determined for schizophrenia, and the semantic priming paradigm is well-suited for addressing this question. In the present report, event-related potentials (ERPs) elicited under conditions assumed to reveal automatic activation (short prime-target interval and low proportion of related words) are compared directly with ERPs elicited under conditions associated with controlled processing (long prime-target interval and high proportion of related words). METHODS: Visual ERPs were recorded during a lexical decision task, in which semantic relationship (associated and unassociated words), expectancy (relatedness proportions), and prime-target interval (250- and 850-msec inter-stimulus intervals [ISIs]) were varied. Diagnosis and expectancy were between-subjects factors; semantic relationship and ISI were repeated measures. The N400 priming effect (enhanced negativity to unassociated words) was compared between 34 male normal control subjects tested once and 37 male schizophrenia inpatients evaluated during their participation in a double-blind haloperidol maintenance therapy and placebo replacement protocol. RESULTS: The N400 priming effect for patients was significantly reduced during both pharmacologic phases, compared with controls. During haloperidol treatment, however, patients showed a significant N400 priming effect over the anterior scalp region and additionally under the automatic activation condition. The N400 priming effect was enhanced under the controlled processing condition for control subjects; this effect was not observed for patients. N400 amplitude elicited under the rapid presentation rate (250-msec ISI) differed between medicated patients and controls; groups did not differ for the 850-msec ISI. CONCLUSIONS: Findings suggest that automatic activation and mechanisms of controlled attention are both disrupted during semantic memory access for schizophrenia patients. Pharmacologic agents, such as haloperidol, might enhance automatic activation of the semantic network in this patient population, as indexed by the N400 component of the ERP.     

Inhibitory effect of smoking on event-related potentials in schizophrenic patients: Comparison with healthy subjects

1. 1. A prior study demonstrated that the P300 peak amplitude of event-related potentials increased during acute withdrawal and smoking resumption in healthy subjects. Here the authors measured the P300 components in schizophrenic patients under similar conditions and compared them to normal controls.

2. 2. The P300 amplitude and area negatively correlated with the daily nicotine intake.

3. 3. The P300 amplitude and area were reduced by smoking resumption following overnight abstinence.

4. 4. The P300 components did not correlate significantly with the Brief Psychiatric Rating Scale or the equivalent neuroleptic dosage.

5. 5. The inhibitory effect of smoking was prevented by pretreatment with nicotine gum.

6. 6. In schizophrenics and healthy subjects, the chronic effects of smoking were similar. However, acute abstinence and smoking resumption decreased the P300 amplitude in schizophrenic patients but increased the amplitude in normal subjects. These results suggest that nicotine differentially affects arousal in schizophrenic patients and healthy subjects.

     

Topographic analysis of auditory event-related potentials associated with acoustic and semantic processing

The topography of auditory event-related potentials (ERPs) was examined during 3 kinds of tasks: selection of a specified real word or nonsense syllable from a list; simple detection of each of the same stimuli without discrimination; and classification of a set of words according to a specified semantic category. The potentials that were associated with the additional processing required by the discriminative tasks were disclosed by subtracting the wave forms obtained in the detection condition from those obtained during discriminative performance. Difference wave forms were also derived between the semantic classification and verbal discriminative ERP to delineate the changes associated with the extraction of word meaning. The topography of the ERP associated with stimulus detection was comparable to that found in previous studies of evoked potentials to non-speech stimuli. This distribution was consistent with 2 cortical generators, one within the supratemporal plane and the other on the lateral surface of the superior temporal gyrus. When discriminative performance was required on the basis of acoustic stimulus properties, the topography of the difference wave form that reflected this discriminative processing extended more posteriorly over temporal cortex. Semantic processing elicited a further posterior extension of ERP components by 330 msec after stimulus onset, as well as longer latency potentials that were not present in the verbal selection task. These differences imply that a more extensive portion of language cortex is engaged in semantic classification than in verbal identification.     

An electrophysiologic study: can semantic context processes be mobilized in patients with thought-disordered schizophrenia?

OBJECTIVE: The aim of this study was to test the hypothesis that reinforcing the structuring of verbal material may bring about an improvement in contextualization processes in patients with formal thought-disordered schizophrenia. METHOD: A total of 38 schizophrenia patients with formal thought disorders and 24 matched healthy control subjects performed 2 lexical decision tasks, involving 2 levels of contextual structuring (with 16.7% and 33% of related words, respectively). The event-related potentials, N400 and late positive component (LPC), and behavioural variables (reaction times and error percentages) were analyzed. RESULTS: A context-structuring effect was observed on LPC, but not on N400. In subjects with schizophrenia, the N400 anomalies (that is, increase in amplitude for the related words and reduction of the N400 effect) persisted in both context-structuring conditions. Similarly, a reduction in LPC amplitude for the unrelated word category, as well as a decrease in the LPC effect, was observed in these patients. CONCLUSIONS: The schizophrenia patients with formal thought disorders did not benefit from the structuring of the context to implement context integration strategies. This deficit appears to be stable. The results are discussed within the framework of a previously published model of language comprehension.     

Mismatch negativity (MMN) in multiple sclerosis: an event-related potentials study in 46 patients.

OBJECTIVE: To assess pre-attentive detection mechanisms indexed by MMN component of auditory Event-Related Potentials (ERPs) in Multiple Sclerosis (MS) patients. METHODS: 46 MS patients (mean age 43.7 years, mean disease duration 10.1 years, mean EDSS 4.6) and 46 matched controls were assessed with ERPs elicited by a passive oddball paradigm using duration deviants. Auditory P50, N1, P2 components were recorded. MMN and P3a components were calculated as the difference potential between deviants and standard stimuli. Eighteen of these 46 patients underwent also global psychometrical assessment and were sorted in cognitively normal and impaired patients. ERPs of these two groups of patients were compared. RESULTS: MS patients showed reduced MMN and P3a areas as compared to controls, besides exogenous N1-P2 complex amplitude reduction. Among the 18 patients investigated with neuropsychological testings, six were cognitively impaired and 12 cognitively unimpaired. Patients with a global cognitive impairment had reduced MMN as compared to cognitively unimpaired patients. CONCLUSIONS: Auditory MMN and P3a components of auditory ERPs are altered in MS patients. MMN alterations are more pronounced in cognitively impaired patients. SIGNIFICANCE: MMN and P3a areas reduction suggests that MS patients are prone to pre-attentive auditory information processing deficits, besides previously described controlled information processing difficulties. Moreover, MMN alterations may represent an objective index of cognitive disturbances in MS patients.     

Speed of face recognition in humans: an event-related potentials study

Event-related potentials (ERPs) were measured while subjects passively looked at a line drawing of a normal face or a line drawing in which parts of the face were scattered so as not to be recognized as a face (scattered face) in order to estimate the speed of face recognition in humans. Because the spatial frequencies of these two types of line drawings were very similar, one could minimize the potentials due to the structure coding stage of the face processing. In addition, passive viewing of these stimuli eliminates the contribution of other processing such as discrimination or memory retrieval. Comparing these two conditions, statistically significant positive potentials were observed in frontal areas from 135ms after stimulus onset for the normal face. These early positive differences were probably due to the face processing per se in human visual recognition. Although statistically significant differences were observed in frontal areas, these are probably related to fusiform or inferior temporal area activation that is often reported using neuro-imaging technologies such as PET or fMRI.     

老年抑郁症患者面孔知觉早期加工的事件相关电位研究

目的 采用事件相关电位技术,探讨老年抑郁症患者面孔识别(区分面孔还是非面孔)和面孔结构信息早期加工的脑电生理机制.方法 被试者包括19例老年抑郁症患者(患者组)及17名健康老年人(对照组).要求被试者观看图片并计数蝴蝶(靶刺激)呈现次数,其他图片(包括面孔、非面孔)为非靶刺激.记录32导脑电波.结果 (1)患者组非靶刺激诱发的P＜,1＞[(3.9±0.8)μV]和N170波幅[(-10.1±1.1)μV]均低于对照组[P<,1>:(6.8±0.8)μV;N170:(-14.4±1.1)μV;P＜0.05～0.01];(2)患者组和对照组均产生显著的N170效应(Nd170)以及N170翻转效应(倒立面孔图像时的N170变化),但患者组右侧颢枕区的N170效应[(-5.8 4±0.9)μV]弱于对照组[(-8.8±0.9)μV,P＜0.05],翻转效应的组间差异则无统计学意义(P＞0.05);(3)患者组靶刺激的P＜,3＞潜伏期[(400 ±10)ms]长于对照组[(368±10)ms;P＜0.05].结论 老年抑郁症患者可能存在面孔基本水平(区分面孔还是非面孔)早期识别的损害,而对面孔结构信息的早期加工则保持相对完整.     

Examining the development of memory for temporal context and its underlying neural processes using event-related potentials

Time is a critical feature of episodic memory—memory for events from a specific time and place (Tulving, 1972). Previous research indicates that temporal memory (memory for ‘when’) is slower to develop than memory for other details (e.g., ‘what’ and ‘where’), with improvements observed across middle and late childhood. The factors that drive these changes are not yet clear. We used an event-related potential (ERP) recognition memory paradigm to investigate the underlying processes of memory for temporal context in middle to late childhood (7−9-year-olds; 10−12-year-olds) and young adulthood. Behaviorally, we observed age-related improvements in the ability to place events in temporal context. ERP analyses showed old/new effects for children and adults. We also found brain-behavior relations for 1) episodic memory (ERP mean amplitude difference between source hits and correctly identified new trials was correlated to behavioral accuracy), and 2) temporal memory (ERP mean amplitude difference between source hits and source error trials was correlated to accuracy of temporal memory judgments). This work furthers our understanding of the cognitive processes and neural signatures supporting temporal memory development in middle to late childhood, and has implications for episodic memory development more broadly.