Neurophysiological evidence for disturbances of conflict processing in patients with schizophrenia

Deficits in cognition are a hallmark of schizophrenia. In the present study, the authors investigated the effects of schizophrenia on the neural correlates of conflict processing in a single-trial version of the Stroop task by using event-related brain potentials. Relative to matched controls, patients with schizophrenia showed increased Stroop interference in response time, but this effect was eliminated when the effect of response slowing was controlled. In controls, conflict processing was associated with a negative wave peaking between 400 and 500 ms (N450) and conflict sustained potential (SP) peaking between 600 and 800 ms after stimulus onset. In patients with schizophrenia, the amplitude of the N450 was significantly attenuated and the conflict SP was absent. These results provide evidence for the existence of altered neural processes associated with conflict processing that may be associated with dysfunction of the anterior cingulate and prefrontal cortex in patients with schizophrenia.     

色-词Stroop任务中的冲突类型述评

在认知控制领域中, 色-词Stroop任务常被用于研究冲突加工的内在机制。本文首先简述色-词Stroop任务中的刺激冲突和反应冲突及研究这两类冲突常用的实验范式。然后介绍这两类冲突的神经动力学特征：事件相关电位研究显示, N450的波幅调整反映了大脑对冲突的监测, 持续电位(sustained potential, SP)的波幅调整反映了大脑对反应冲突的解决; 核磁共振成像研究显示, 前扣带回、背外侧前额叶分别在反应冲突的监测、认知控制的执行上扮演着重要的角色。文章最后针对目前研究范式存在的问题提出了改进方法和认知神经研究的新方向。     

Is conflict monitoring supramodal? Spatiotemporal dynamics of cognitive control processes in an auditory Stroop task

The electrophysiological correlates of conflict processing and cognitive control have been well characterized for the visual modality in paradigms such as the Stroop task. Much less is known about corresponding processes in the auditory modality. Here, electroencephalographic recordings of brain activity were measured during an auditory Stroop task, using three different forms of behavioral response (overt verbal, covert verbal, and manual), that closely paralleled our previous visual Stroop study. As was expected, behavioral responses were slower and less accurate for incongruent than for congruent trials. Neurally, incongruent trials showed an enhanced fronto-central negative polarity wave (N_inc), similar to the N450 in visual Stroop tasks, with similar variations as a function of behavioral response mode, but peaking ~150 ms earlier, followed by an enhanced positive posterior wave. In addition, sequential behavioral and neural effects were observed that supported the conflict-monitoring and cognitive adjustment hypothesis. Thus, while some aspects of the conflict detection processes, such as timing, may be modality dependent, the general mechanisms would appear to be supramodal.     

概化理论预算限制下最佳样本量估计

概化理论广泛应用于各种心理测评实践中。当有预算限制时,概化理论需要考虑如何设计一个测量可靠性相对较高且可行性也相对较强的测量程序,这就要求通过某些途径估计最佳样本量。拉格朗日乘法是概化理论预算限制下最佳样本量估计较为成熟的方法。探讨了概化理论预算限制下最佳样本量估计的一些影响因素,如受总预算舍入的影响等,也提出了一些后续改善的建议,如推导出拉格朗日乘法的统一公式等     

Automaticity in reading and the Stroop task: testing the limits of involuntary word processing

We investigated the parameters of involuntary word reading in the Stroop task in 7 experiments. Experiments 1-4 varied response modality and the presence of congruent word trials in a test of the claim that presenting a Stroop color word with only one letter in the target color eliminates the Stroop effect. Experiments 5 and 6 addressed the roles of spatial attention and orthographic processing as possible mechanisms behind the reduction of Stroop effects with the single-letter format. Experiment 7 investigated the limits of involuntary reading under optimal conditions for selective processing of rectangular color patch targets. We found that the single-letter format reduced but never eliminated Stroop effects, spatial attention but not orthographic processing plays a role in the effect of the single-letter format, and word reading is not completely prevented even with austere presentation conditions. We conclude with a defense of the involuntariness criterion for automaticity in the Stroop task, particularly when word reading is viewed in the context of a skilled performance.     

Investigating the modality specificity of response selection using a temporal flanker task

The neurocognitive architecture for response selection is uncertain. Some theorists suggest that it is mediated by an amodal central mechanism, whereas others propose a set of independent control mechanisms. In a functional neuroimaging experiment, we investigated the nature of response selection by examining how its underlying brain mechanisms are affected by stimulus modality. To do this, we used a modified flanker task, in which the target and flanker (distractor) stimuli differed in time rather than space, making it accessible for both visual and auditory stimuli. As in the traditional flanker task, larger reaction times were observed for incongruent than congruent trials (i.e., a congruency effect) for both modalities. Congruency affected brain activation for both modalities in prefrontal cortex, parietal cortex, and the putamen. Modality-dependent activation was found in additional prefrontal and parietal regions for the visual modality and in left inferior prefrontal cortex for the auditory modality. Modality-dependent activity specifically related to response congruency was also found in sensory cortical regions. These data suggest that modality affects the brain regions throughout the cortex mediating response selection even for conceptually identical stimuli and tasks. They are consistent with the hypothesis that (at least partially) independent brain networks mediate response selection and that input modality may be a powerful factor for organizing neural activity to support task performance.     

Anterior cingulate cortex and cognitive control: Neuropsychological and electrophysiological findings in two patients with lesions to dorsomedial prefrontal cortex

Whereas neuroimaging studies of healthy subjects have demonstrated an association between the anterior cingulate cortex (ACC) and cognitive control functions, including response monitoring and error detection, lesion studies are sparse and have produced mixed results. Due to largely normal behavioral test results in two patients with medial prefrontal lesions, a hypothesis has been advanced claiming that the ACC is not involved in cognitive operations. In the current study, two comparably rare patients with unilateral lesions to dorsal medial prefrontal cortex (MPFC) encompassing the ACC were assessed with neuropsychological tests as well as Event-Related Potentials in two experimental paradigms known to engage prefrontal cortex (PFC). These included an auditory Novelty Oddball task and a visual Stop-signal task. Both patients performed normally on the Stroop test but showed reduced performance on tests of learning and memory. Moreover, altered attentional control was reflected in a diminished Novelty P3, whereas the posterior P3b to target stimuli was present in both patients. The error-related negativity, which has been hypothesized to be generated in the ACC, was present in both patients, but alterations of inhibitory behavior were observed. Although interpretative caution is generally called for in single case studies, and the fact that the lesions extended outside the ACC, the findings nevertheless suggest a role for MPFC in cognitive control that is not restricted to error monitoring.     

One night of sleep deprivation affects reaction time, but not interference or facilitation in a Stroop task

The Stroop color-naming task is one of the most widely studied tasks involving the inhibition of a prepotent response, regarded as an executive function. Several studies have examined performance on versions of the Stroop task under conditions of acute sleep deprivation. Though these studies revealed effects on Stroop performance, the results often do not differentiate between general effects of sleep deprivation on performance and effects specifically on interference in the Stroop task. To examine the effect of prolonged wakefulness on performance on the Stroop task, we studied participants in a 40-h "constant routine" protocol during which they remained awake in constant conditions and performed a Stroop color-naming task every two hours. We found that reaction time was slowest when the color and word did not match (incongruent), fastest when the color and word did match (congruent), and intermediate when participants named the color of the non-word stimulus (neutral). Performance on all three trial types degraded significantly as a function of time awake. Extended wakefulness did not significantly change the additional time needed to respond when the color and word did not match (Stroop interference), nor did it change the amount of facilitation when color and word matched. These results indicate that one night of sleep deprivation influences performance on the Stroop task by an overall increase in response time, but does not appear to impact the underlying processes of interference or facilitation. The results suggest that the degree to which an "executive function" is affected by sleep deprivation may depend on the particular executive function studied and the degree to which it is subserved by the prefrontal cortex.     

Components of Stroop-like interference in picture naming

The semantic interference effect observed in Stroop tasks and picture-word interference tasks might be due to the previous confounding of semantic similarity with task relevance (in the Stroop task) and with perceptual similarity (in the picture-word interference task). A picture-word variant of the Stroop task was devised in which the factors of task relevance and perceptual similarity were controlled. The distractor conditions allowed for the examination of four types of context effects. The results show that the overall Stroop-like interference effect can be decomposed into interference effects due to (1) a semantic relation between distractor and target, (2) the semantic relevance of the distractor word in the task at hand, (3) the presence of the distractor word in the response set, and (4) the mere presence of a word. Implications of these findings for the locus or loci of Stroop and picture-word interference effects are discussed. It is concluded that distractor words in Stroop-like naming tasks interfere mainly in the process of name retrieval.     

Adding fear to conflict: A general purpose cognitive control network is modulated by trait anxiety

Studies of cognitive control show that the dorsal anterior cingulate cortex (dACC) and dorsolateral prefrontal cortex are involved in the detection and resolution of cognitive conflict. However, the neural and behavioral mechanisms underlying emotional interference effects are less consistent. We used fMRI during emotional and nonemotional versions of a facial Stroop task to investigate the effects of emotional stimuli on cognitive control. In the full group there was limited evidence that different prefrontal circuits manage conflict arising from emotional and nonemotional distractors. However, individual differences in trait anxiety affected both behavioral performance and neural activity during the emotional task. Relative to low-anxiety (LA) subjects, high-anxiety (HA) subjects showed greater amygdala activity to task-relevant emotional information and impaired performance and greater conflict-related activity in the dACC when emotional content was task-irrelevant. Only LA subjects activated rostral ACC during the emotional task. This is consistent with cognitive models of individual differences that hypothesize deficient control of task-irrelevant emotional information in HA subjects. Additional behavioral and fMRI results from this study may be downloaded from http://cabn.psychonomic-journals .org/content/supplemental.     

Perceived control in continuous loud noise

The effects of two types of perceived control were assessed for performance during and following exposure to continuous loud noise at 90 dBC. Subjects performed a tracking task during exposure and the Stroop test in the period following exposure. Control could be effected either (1) by attenuating the intensity of the noise or (2) by reducing the difficulty of the tracking task. In both cases subjects were encouraged not to exercise control. Performance in treatments involving loud (90 dBC) and soft (55 dBC) noise served as baseline conditions. Perceived control of task difficulty accentuated the tendency for root-mean-square error to rise during the tracking task. There were no significant effects of noise intensi ty on tracking performance. Loud noise reduced the incidence of errors in the Stroop test but perceived control failed to influence this effect. The results are discussed in terms of the generality of perceived control phenomena.     

Interference produced by emotional conflict associated with anterior cingulate activation

The anterior cingulate cortex (ACC) is involved in cognition and emotion. In the classic Stroop task, presentation of stimuli that are in response conflict with one another produces activation in the caudal ACC. In the emotional Stroop task, presentation of emotionally salient stimuli produces activation in the rostral ACC. Presentation of stimuli that are emotionally conflicting should activate the caudal ACC; stimuli that are emotionally salient should activate the rostral ACC. We tested this prediction using functional magnetic resonance imaging while subjects made emotional valence judgments of words overlaid on emotional faces (word-face Stroop task). Emotionally incongruent pairs were responded to more slowly than emotionally congruent pairs. Emotionally incongruent trials were associated with increased activation within the caudal ACC, whereas no ACC activation was found in response to emotional saliency. These results support the conflict-monitoring model of caudal ACC and extend this function to conflict within the domain of emotional stimuli.     

Interference resolution: Insights from a meta-analysis of neuroimaging tasks

A quantitative meta-analysis was performed on 47 neuroimaging studies involving tasks purported to require the resolution of interference. The tasks included the Stroop, flanker, go/no-go, stimulus-response compatibility, Simon, and stop signal tasks. Peak density-based analyses of these combined tasks reveal that the anterior cingulate cortex, dorsolateral prefrontal cortex, inferior frontal gyrus, posterior parietal cortex, and anterior insula may be important sites for the detection and/or resolution of interference. Individual task analyses reveal differential patterns of activation among the tasks. We propose that the drawing of distinctions among the processing stages at which interference may be resolved may explain regional activation differences. Our analyses suggest that resolution processes acting upon stimulus encoding, response selection, and response execution may recruit different neural regions.     

Impaired executive functions in subjects with frequent nightmares as reflected by performance in different neuropsychological tasks

Nightmare disorder is a prevalent parasomnia characterized by vivid and highly unpleasant dream experiences during night time sleep. The neural background of disturbed dreaming was proposed to be associated with impaired prefrontal and fronto-limbic functioning during REM sleep. We hypothesized that the impaired prefrontal and fronto-limbic functioning in subjects with frequent nightmares would be reflected at the behavioral level during waking tasks as well. 35-35 Subjects with frequent nightmares and matched controls participated in Study 1, involving an Emotional Go/NoGo, an Emotional Stroop task, and a Verbal Fluency task. Nightmare subjects exhibited longer reaction times in the Emotional Go/NoGo and Emotional Stroop tasks. Moreover, they committed more perseveration errors and showed less fluent word generation in the Verbal Fluency task. Nightmare subjects showed an overall slowing irrespective of the valence of the stimuli. While the effects of sleep quality and waking anxiety were associated to these deficits in some cases, these factors could not solely explain the difference between the two groups. In Study 2, 17 subjects with frequent nightmares and 18 controls were compared by a Color-word and an Emotional, block design Stroop task in order to avoid the slow effects of emotional interference potentially caused by previous items. Nightmare subjects were characterized by an overall slowing in the Emotional Stroop task, irrespective of the valence of the stimuli. In the Color-word Stroop task, nightmare subjects were not significantly slower in comparison with controls. Our results suggest that individuals with frequent nightmares are impaired in executive tasks involving the suppression of task-irrelevant semantic representations.     

选择损耗自我控制资源:取舍效应还是信息加工难度效应?

研究以自我控制的资源模型为理论框架,从选择难度特征的视角出发,通过两项实验考察选择损耗自我控制资源的成因。结果发现,高取舍冲突组被试的stroop任务成绩显著低于低取舍冲突组被试,高、低阅读难度组被试的stroop任务成绩差异不显著;为自己做选择组被试的stroop任务成绩显著低于为他人做选择组被试,完成3选项和4选项任务组被试的stroop任务成绩差异不显著。研究表明,选择损耗效应是由选择的取舍难度而非信息加工难度造成。。     

Stimulus–response translation in manual and vocal modality: Is age‐related slowing influenced by changes in working memory functioning?

In some conditions, age‐related slowing rates are higher for manual than for vocal responses. The interaction between age and response modality was examined in four experiments in which the performance of younger (M = 22.6 years) and older (M = 70.8 years) adults was compared under various stimulus–response mapping rules. The interaction effect was not observed in a simple localisation task on which the manual modality had an advantage in both age groups (Experiment 1). When congruence between stimulus and response was reduced (Experiment 2), manual responses were disproportionately slowed in older participants. In conceptual and size comparison tasks (Experiment 3), the age‐by‐modality effect was not influenced by working memory load during the interval between the first and the second stimulus presentation. In an identification task, age‐related slowing effects were less when responses were spoken names than when nonwords were used as labels (Experiment 4). These results indicate that older participants experience a specific difficulty in activating arbitrary S–R mapping rules during executive control.     

Information-processing modules and their relative modality specificity

This research uses fMRI to understand the role of eight cortical regions in a relatively complex information-processing task. Modality of input (visual versus auditory) and modality of output (manual versus vocal) are manipulated. Two perceptual regions (auditory cortex and fusiform gyrus) only reflected perceptual encoding. Two motor regions were involved in information rehearsal as well as programming of overt actions. Two cortical regions (parietal and prefrontal) performed processing (retrieval and representational change) independent of input and output modality. The final two regions (anterior cingulate and caudate) were involved in control of cognition independent of modality of input or output and content of the material. An information-processing model, based on the ACT-R theory, is described that predicts the BOLD response in these regions. Different modules in the theory vary in the degree to which they are modality-specific and the degree to which they are involved in central versus peripheral cognitive processes.     

Response inhibition and avoidance of virtual obstacles during gait in healthy young and older adults

Adjustments of preplanned steps are essential for fall avoidance and require response inhibition. Still, inhibition is rarely tested under conditions resembling daily living. We evaluated the ability of young and older adults to modify ongoing walking movements using a novel precision step inhibition (PSI) task combined with an auditory Stroop task.Healthy young (YA, n = 12) and older (OA, n = 12) adults performed the PSI task at 4 individualized difficulty levels, as a single and dual task (DT). Subjects walked on a treadmill by stepping on virtual stepping stones, unless these changed color during approach, forcing the subjects to avoid them. OA made more failures (40%) on the PSI task than YA (16%), but DT did not affect their performance. In combination with increased rates of omitted Stroop task responses, this indicates a “posture first” strategy. Yet, adding obstacles to the PSI task significantly deteriorated Stroop performance in both groups (the average Stroop composite score decreased by 13% in YA and 27% in OA). Largest deficit of OA was observed in rates of incorrect responses to incongruent Stroop stimuli (OA 35% and YA 12%), which require response inhibition. We concluded that the performance of OA suffered specifically when response inhibition was required.