Impaired response selection in schizophrenia: Evidence from the P3 wave and the lateralized readiness potential

Reaction times (RTs) are substantially prolonged in schizophrenia patients, but the latency of the P3 component is not. This suggests that the RT slowing arises from impairments in a late stage of processing. To test this hypothesis, 20 schizophrenia patients and 20 control subjects were tested in a visual oddball paradigm that was modified to allow measurement of the lateralized readiness potential (LRP), an index of stimulus-response translation processes. Difference waves were used to isolate the LRP and the P3 wave. Patients and control subjects exhibited virtually identical P3 difference waves, whereas the LRP difference wave was reduced in amplitude and delayed in latency in the patients. These results indicate that, at least in simple tasks, the delayed RTs observed in schizophrenia are primarily a consequence of impairments in the response selection and preparation processes that follow perception and categorization.     

The functional locus of the lateralized readiness potential

The lateralized readiness potential (LRP) is considered to reflect motor activation and has been used extensively as a tool in elucidating cognitive processes. In the present study, we attempted to more precisely determine the origins of the LRP within the cognitive system. The response selection and motor programming stages were selectively manipulated by varying symbolic stimulus response compatibility and the time to peak force of an isometric finger extension response. Stimulus response compatibility and time to peak force affected response latency, as measured in the electromyogram, in a strictly additive fashion. The effects of the experimental manipulations on stimulus- and response-synchronized LRPs indicate that the LRP starts after the completion of response-hand selection and at the beginning of motor programming. These results allow a more rigorous interpretation of LRP findings in basic and applied research.     

Locus of the effect of temporal preparation: evidence from the lateralized readiness potential

It is well established that reaction time (RT) is shorter when a response signal is preceded by a warning signal, because the warning signal causes the participant to prepare for the upcoming response. A review of chronometric and psychophysiological studies reveals the prevailing view that this temporal preparation operates mainly at a motor level speeding up rather late processes. To assess the locus of this preparation effect, we conducted two experiments employing the lateralized readiness potential (LRP). Contrary to this prevailing view, the results of both experiments clearly indicate that temporal preparation enhances the processing speed of relatively early processes, because a manipulation of temporal uncertainty affected RT, the P300 latency, and the stimulus-to-LRP interval but not the LRP-to-keypress interval.     

The lateralized readiness potential and response kinetics in response-time tasks

Previous studies have found that the magnitude of the lateralized readiness potential (LRP) at the time of response initiation is constant across spontaneous variations in response time in both cued and uncued, speeded tasks. Other studies have found that the LRP is also unaffected by instructed changes in peak response force and time to peak force in cued, self-paced tasks, but that the LRP is sensitive to instructed changes in force gain rate in uncued, self-paced tasks. The present study examined the LRP in an uncued, speeded task as a function of response time and several measures of response kinetics. The magnitude of the LRP at the time of electromyographic onset was constant across spontaneous variations in all measures. The peak of the contingent negative variation did vary as a function of peak response force and integrated force to peak, but not response time. These findings support the idea that the LRP in speeded tasks is a selective, on-line index of the preparation associated with using a particular hand, and is not an index of the elements of motor programming that determine subsequent response kinetics.     

The lateralized readiness potential: relationship between human data and response activation in a connectionist model.

Psychophysiological measures such as the lateralized readiness potential (LRP) have been used to study information processing in the Eriksen flankers task. The data provided by these measures are consistent with a continuous flow theory, which proposes that the output of stimulus evaluation is continuously available to the response channels. Cohen et al. (1992) realized this theory in a connectionist model and showed that its behavior corresponded to that of human subjects in the flankers task. We report here a modification of the model and an analysis of the degree to which simulated LRPs (based on the activation functions of the response units of the model) resemble the actual LRPs of human subjects in the same task. Across a variety of different experimental conditions and outcomes, there was a marked correspondence between the simulated and actual LRPs. These observations strengthen the propriety of the connectionist model and of the continuous flow theory on which it is based.     

The lateralized readiness potential preceding brief isometric force pulses of different peak force and rate of force production

Previous studies have reported that the lateralization of the readiness potential is unaffected by force amplitude of brief unimanual responses. However, Because those studies did not spectify rate of force production, response force probably was mainly controlled by force unit duration rather than by recruitment of force units, which may explain this negative finding. To enforce recruitment control, we factorially combined peak force (10% or 50% of maximal voluntary finger force) and time to peak force (100 or 200 ms). A precue provided advance information about the responding index finger (left vs. right). After 1 s, the imperative stimulus followed, requiring a brisk isometric flexion of the specified index finger. Symmetric effects, maximal at the vertex, of both force and rate of force production were observed 200–100 ms before the imperative stimulus in stimulus-synchronized averages and 200–100 ms before response onset in response-synchronized averages. However, neither force nor rate to force production affected the lateralized readiness potential. We conclude that this measure does not reflect movement parameters but appears to indicate an abstract preparation of lateralized response channels.     

Detecting the onset of the lateralized readiness potential: a comparison of available methods and procedures

Studies that measure the onset of the lateralized readiness potential (LRP) could well provide researchers with important new data concerning the information-processing locus of experimental effects of interest. However, detecting the onset of the LRP has proved difficult. The present study used computer simulations involving both human and artificial data, and both stimulus- and response-locked effects, to compare a wide variety of techniques for detecting and estimating differences in the onset latency of the LRP. Across the two sets of simulations, different techniques were found to be the most accurate and reliable for the analysis of stimulus- and response-locked data. On the basis of these results, it is recommended that regression-based methods be used to analyze most LRP data.     

Response activation impairments in schizophrenia: evidence from the lateralized readiness potential

Previous research has demonstrated deficits in preresponse motor activity in schizophrenia, as evidenced by a reduced lateralized readiness potential (LRP). The LRP deficit could be due to increased activation of the incorrect response (e.g., failure to suppress competition) or to reduced activation of the correct response (e.g., a low-level impairment in response preparation). To distinguish these possibilities, we asked whether the LRP impairment is increased under conditions of strong response competition. We manipulated the compatibility of stimulus-response mappings (Experiment 1) and the compatibility of the target with flankers (Experiment 2). In both experiments, the patient LRP was reduced as much under conditions of low response competition as under high competition. These results are incompatible with a failure of patients to suppress competition and are instead consistent with a deficit in activating the correct response.     

The structure of motor programming: Evidence from reaction times and lateralized readiness potentials

There is a widely accepted notion that movement elements are assembled prior to movement execution in a central motor programming stage. However, it is not clear how this stage is structured—whether it is a unitary stage allowing different motor parameters to cross talk or whether there are several independent processes dealing with each motor parameter. We addressed this question by orthogonally manipulating two movement‐related factors: response sequence complexity and movement duration. Both factors yielded main effects on reaction time but no interaction. Additive effects of both factors on the onsets of response‐ but not stimulus‐synchronized lateralized readiness potentials suggest separable motoric loci of sequence complexity and duration. These findings are at variance with the notion of a unitary movement programming stage.     

Preparation of response force and movement direction: onset effects on the lateralized readiness potential

Two experiments assessed the preparatory effects of advance information about response force and movement direction on the lateralized readiness potential (LRP). In a choice reaction time (RT) task, an imperative stimulus required an isometric flexion or an extension of the left or right index finger. Prior information about response force or about movement direction reduced RT and shortened the interval from the onset of the imperative stimulus up to the onset of the LRP. Advance information, however, about direction but not about force decreased the interval from LRP onset to the onset of the overt response. The identical pattern of results was obtained in a second experiment, in which each participant performed both precue conditions. The findings of both experiments support the notion that response force is specified before movement direction. These results are consistent with the view accordingly different mechanisms are involved in the specification of muscle force and movement direction.     

Partial information can be transmitted in an auditory channel: inferences from lateralized readiness potentials

With the two-choice go/no-go paradigm, we investigated whether timbre attribute can be transmitted as partial information from the stimulus identification stage to the response preparation stage in auditory tone processing. We manipulated two attributes of the stimulus: timbre (piano vs. violin) and acoustic intensity (soft vs. loud) to ensure an earlier processing of timbre than intensity. We associated the timbre attribute more with go trials. Results showed that lateralized readiness potentials (LRPs) were consistently elicited in no-go trials. This showed that the timbre attribute had been transmitted to the response preparation stage before the intensity attribute was processed in the stimuli identification stage. Such a result provides evidence for the continuous model and asynchronous discrete coding (ADC) model in information processing. We suggest that partial information can be transmitted in an auditory channel.     

The usefulness of partial information: effects of go probability in the choice/Nogo task.

In the present study, we examined whether the use of partial information for response preparation depends on the utility of that partial information for meeting task demands. Using a choice/Nogo task, the utility of the partial information was varied by manipulating the proportion of Go relative to Nogo signals, and preliminary response preparation was indexed by the degree of lateralized readiness potential (LRP) activity on Nogo trials. The Nogo LRP was clearly present when Go probability was high (67% Go) and, to a lesser extent, when Go and Nogo signals were equiprobable. However, the Nogo LRP disappeared when the probability of a Go signal was low (25% Go). This pattern of results supports the hypothesis that response preparation will be based on partial stimulus information only when the information has significant utility in the context of the overall task requirements.     

The application of jackknife-based onset detection of lateralized readiness potential in correlative approaches

The onset of the lateralized readiness potential (LRP) represents an interesting parameter within mental chronometry. According to Miller, Patterson, and Ulrich (1998), reliability increases when LRP onsets are detected in jackknifed LRP waveforms. Until now, jackknifed LRP onsets could be analyzed in factorial designs only. The aim of the present study was to extend the application of jackknifing to correlative approaches (e.g., in personality research). Using different onset scoring techniques, in several simulations run on realistic LRP data jackknifing and single-subject procedures were compared regarding their estimates of a simulated true correlation. For all scoring techniques but regression, jackknifed coefficients were on average higher than the respective single-subject coefficients, and statistical power was higher. Overall, combining jackknifing with a 50%-relative onset criterion is recommended.     

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。     

老年糖尿病人P300认知电位改变及相关因素分析

目的：了解老年糖尿病人P300认知电位的改变及与病程、糖代谢及并发症的关系。方法：采用听觉oddball序列刺激的诱发电位方法对50例老年糖尿病人及20例健康老年人进行测试。结果：糖尿病组与对照组比较,糖尿病并腔隙性脑梗塞组与无脑梗塞组比较P300波潜伏期显著延长,P300波波幅显著降低,糖尿病组P300波潜伏期和波幅与病程长短、糖化血红蛋白及有无高血压病无明显相关。结论：老年糖尿病人比正常老年人P300波潜伏期明显延长,P300波波幅明显降低,合并腔隙性梗塞可能是其P300波改变的主要原因之一。     

癫(癎)儿童事件相关电位P300检测报告

目的:探讨事件相关电位(ERP)的P300成分检测对癫癎儿童认知功能的评价。方法:利用ERP、韦氏儿童智力量表中国修订版(WIS-CR)对32例癫癎儿童进行P300测定和心理评估,以28例性别、年龄相匹配的正常儿童作对照。结果:与正常对照组比较,癫癎组儿童总智商(FIQ)、语言智商(VIQ)和操作智商(PIQ)得分均明显降低(P<0．01),32例癫癎患儿中有28％有智能障碍;ERP的P300波潜伏期也明显延长,P<0．01。结论:癫癎儿童易发生智力障碍,P300波潜伏期检测能早期、客观、准确地评价癫癎儿童的认知功能状况。     

A carry-over task rule in task switching: An ERP investigation using a Go/Nogo paradigm

Investigations of executive control using a task-switching paradigm have consistently found longer reaction times for task-switch trials than task-repetition trials. This switch cost may result from interference by a stimulus-response (SR) rule carried over from the preceding alternative task. We examined event-related brain potential (ERP) evidence for such carry-over effects using a combined paradigm of task switching with Go/Nogo; Nogo trials, which require no response execution, should expose carry-over effects from preceding trials. On Go trials, twelve participants performed a button-pressing task in compatible (hand and signal direction consistent) and incompatible conditions, which switched predictably every three trials. Reaction times were longer on switch than on repetition trials. On compatible switch trials, a stimulus-locked lateralized readiness potential (sLRP) for Nogo stimuli revealed a positive dip, suggesting incorrect response activation in the early automatic process that was induced by a SR rule carried over from the preceding task.     

行为问题儿童听觉事件相关电位P300对照研究

目的:探讨行为问题儿童听觉事件相关电位P300特点.方法:用Achenbach儿童行为问卷(CBCL)和中国联合型瑞文测验(CRT-C2)筛选行为问题儿童,并按同性别、同年龄进行1:2配对;采用odd模式测试听觉事件相关电位.结果:①问题组儿童的P300各项指标与对照组儿童无显著差异;②混合问题组P300潜伏期较单一问题组延迟(P<0.05),Pz点P300的基线波幅混合问题组与单一问题组的差异接近有统计学意义.③行为问题儿童Pz点P300基线波幅与行为问卷总分呈显著负相关(P<0.05).结论:行为问题较为严重的儿童可能有认知功能损害.     

癫痫儿童认知电位P300及其影响因素分析

目的：研究癫痫儿童认知电位P300E事件相关电位（ERP）的P300成分]及其影响因素。方法：检测分析85例癫痫儿童及63例健康对照的认知电位P300,并探讨癫痫儿童认知电位P300各影响因素的作用。结果：以健康儿童作比较,癫痫儿童P300潜伏期延长．差肄有显著意义（P〈0．01）,波幅降低。差异也有显著意义（P〈0．05）;Logistic回归分析显示发病年龄早和发作频繁是癫痫儿童P300潜伏期延长、认知功能损害加重的危险因素,减少发作频率为其保护因素。结论：认知电位P300可以较客观及早地反映癫痫儿童的认知状况。应于患病早期积极抗癫痫治疗,降低认知功能受损的发生率。     

血管性痴呆患者事件相关电位P300及相关因素研究

目的：研究血管性痴呆患者的事件相关电位P300及相关因素诊断的应用。方法：对42例VD和36例无痴呆脑梗死患者进行听觉P300检测，并进行病因、病变部位等危险因素对比分析。结果：VD组常有高血压、糖尿病、震颤麻痹、皮质下病灶、双侧半球病灶及脑萎缩，并有2次以上座中发生。VD组N1、P2、N2、和P3潜伏期均明显延长，P2、P3波幅分别降低，与对照组比较差异有显著意义（P＜0．01）。结论：高血压、糖尿病、震颤麻痹，反复卒中、皮质病灶、多发性病灶、脑萎缩均是VD的危险因素，与VD的发生、发展有关。事件相关电位P300是一种客观的神经生理学指标，对VD的早期诊断有实用价值。