The Stroop's test evokes a negative brain potential, the N400

The temporal dynamics of the Stroop effect from childhood to young and older adulthood

The processes involved in the Stroop task/effect are thought to involve conflict detection and resolution stages. Little is known about the evolution of these two components over the lifespan. It is well admitted that children and older adults tend to show longer response latencies than young adults. The present study aims at clarifying the rational of such changes from childhood to adulthood and in aging by comparing the impacted cognitive processes across age groups. More precisely, the aim was to clarify if all processes take more time to be executed, hence implying that longer latencies rely mainly on processing speed or if an additional process lengthens the resolution of the conflict in children and/or older adults. To this aim we recorded brain electrical activity using EEG in school-age children, young and older adults while they performed a classic verbal Stroop task. The signal was decomposed in microstate brain networks, and age groups and conditions were compared. Behavioral results evolved following an inverted U-shaped curve. In children, different brain states from the ones observed in adults were highlighted, both in the conflict detection and resolution time-windows. Longer latencies in the incongruent condition were mainly attributed to an overly increased duration of the microstates involved in the conflict resolution time window. In aging, the same microstate maps were reported for both young and older adult groups. The differences in performances between groups could be explained by a disproportionally long conflict detection phase, even compressing the latest stage of response articulation. These results tend to favor a specific immaturity of the brain networks involved coupled with a slowing of the processes in children, while cognitive decline could be mostly explained by a general slowing.

Stroop in motion: Neurodynamic modulation underlying interference control while sitting, standing, and walking

There is conflicting evidence about how interference control in healthy adults is affected by walking as compared to standing or sitting. Although the Stroop paradigm is one of the best-studied paradigms to investigate interference control, the neurodynamics associated with the Stroop task during walking have never been studied. We investigated three Stroop tasks using variants with increasing interference levels - word-reading, ink-naming, and the switching of the two tasks, combined in a systematic dual-tasking fashion with three motor conditions - sitting, standing, and treadmill walking. Neurodynamics underlying interference control were recorded using the electroencephalogram. Worsened performance was observed for the incongruent compared to congruent trials and for the switching Stroop compared to the other two variants. The early frontocentral event-related potentials (ERPs) associated with executive functions (P2, N2) differentially signaled posture-related workloads, while the later stages of information processing indexed faster interference suppression and response selection in walking compared to static conditions. The early P2 and N2 components as well as frontocentral Theta and parietal Alpha power were sensitive to increasing workloads on the motor and cognitive systems. The distinction between the type of load (motor and cognitive) became evident only in the later posterior ERP components in which the amplitude non-uniformly reflected the relative attentional demand of a task. Our data suggest that walking might facilitate selective attention and interference control in healthy adults. Existing interpretations of ERP components recorded in stationary settings should be considered with care as they might not be directly transferable to mobile settings.

Effects of 12 weeks of aerobic exercise combined with resistance training on neurocognitive performance in obese women

Background/Objectives

To the best of our knowledge, there have been no previous studies conducted on the long-term effects of an exercise intervention on deficits in inhibitory control in obese individuals. The aim of this study was thus to examine the effect of 12 weeks of a combination of aerobic and resistance exercise on behavioral and cognitive electrophysiological performance involving cognitive interference inhibition in obese individuals.

Methods

Thirty-two qualified healthy obese women were randomly divided into either an exercise group (EG, age: 34.76 ± 5.52 years old; BMI: 29.35 ± 3.52 kg/m2) or a control group (CG, age: 33.84 ± 7.05 years old; BMI: 29.61 ± 4.31 kg/m2). All participants performed the Stroop task, with electrophysiological signals being collected simultaneously before and after a 12-week intervention. The estimated V̇O2max, muscular strength, and body fat percentage (measured with dual-energy X-ray absorptiometry) were also assessed within one week before and after the intervention. Participants in the EG group engaged in 30 min of moderate-intensity aerobic exercise combined with resistance exercise, 5 sessions per week for 12 weeks, while the participants in the CG group maintained their regular lifestyle without engaging in any type of exercise.

Results

The results revealed that although a 12-week exercise intervention did not enhance the behavioral indices [e.g., accuracy rates (ARs) and reaction times (RTs)] in the EG group, significantly shorter N2 and P3 latencies and greater P2 and P3 amplitudes were observed. Furthermore, the fat percentage distribution (e.g. total body fat %, trunk fat %, and leg fat %) and level of physical fitness (e.g. estimated V̇O2max and muscular strength) in the EG group were significantly improved. The changes prior to and after the intervention in the P3 amplitude and trunk fat percentage were significantly negatively correlated in the EG group (r = -0.521, p = 0.039).

Conclusions

These findings suggested that 12 weeks of aerobic exercise combined with resistance exercise in obese women affects cognitive function broadly, but not specifically in terms of inhibitory control. The percentage of decreased trunk fat may play a potential facilitating role in inhibition processing in obesity.

Electrophysiological Evidence of Anticipatory Cognitive Control in the Stroop Task

The Stroop task has been largely used to explore the ability to inhibit the automatic process of reading when reporting the ink color of incongruent color-words. Given the extensive literature regarding the processes involved in task performance, here we aimed at exploring the anticipatory brain activities during the Stroop task using the event-related potential (ERP) method. To accomplish this, eighteen participants performed two different blocks where neutral words were intermixed with congruent and incongruent words, respectively. Results revealed consistent pre-stimulus activity over the frontal, premotor and parietal brain areas. The premotor and the parietal activities were also modulated by the Stroop effect, being more enhanced in the incongruent than in the congruent blocks. Present findings add on the current literature pointing at an unexplored locus of anticipatory cognitive control during task preparation, thus offering a new way to investigate top-down preparatory processes of performance control in the Stroop task.

The Influence of Action Video Gaming Experience on the Perception of Emotional Faces and Emotional Word Meaning

Action video gaming (AVG) experience has been found related to sensorimotor and attentional development. However, the influence of AVG experience on the development of emotional perception skills is still unclear. Using behavioral and ERP measures, this study examined the relationship between AVG experience and the ability to decode emotional faces and emotional word meanings. AVG experts and amateurs completed an emotional word-face Stroop task prior to (the pregaming phase) and after (the postgaming phase) a 1 h AVG session. Within-group comparisons showed that after the 1 h AVG session, a more negative N400 was observed in both groups of participants, and a more negative N170 was observed in the experts. Between-group comparisons showed that the experts had a greater change of N170 and N400 amplitudes across phases than the amateurs. The results suggest that both the 1 h and long-term AVG experiences may be related to an increased difficulty of emotional perception. Furthermore, certain behavioral and ERP measures showed neither within- nor between-group differences, suggesting that the relationship between AVG experience and emotional perception skills still needs further research.

Complex Time-Dependent ERP Hemispheric Asymmetries during Word Matching in Phonological, Semantic and Orthographical Matching Judgment Tasks

Language-induced asymmetry to single word reading has been well investigated in past research. Less known are the complex processes and related asymmetries occurring when a word is compared with the previous one, according to specific tasks. To this end, we used a paradigm based on 80 sequential word pair comparisons and three blocked tasks: phonological, semantic and orthographical matching judgment. Participants had to decide whether the target word (W2) did or did not match the prime word (W1), presented 2 sec before, according to the task. The event-related potentials (ERPs) evoked by W2 in 20 participants have been analyzed. The first negative wave, the Recognition Potential (RP), peaking at about 120 ms over parietal sites, showed greater amplitude at left sites in all tasks, thus revealing the typical left-lateralization. At frontal sites, only the phonological task showed left lateralization. The following N400 (300–450 ms) showed an interesting interaction: Match trials elicited greater left asymmetry on frontal regions to phonological than to semantic than to visual-perceptual tasks, whereas mismatch trials induced an inverted asymmetry, marked by greater amplitude over right frontal sites, regardless of the task. Concerning the late N400 (450–600 ms), phonological and semantic tasks showed an overlapping pattern, with left lateralization in match and right lateralization in mismatch conditions. Results point to complex task- and time-dependent hemispheric asymmetries in word matching.

Neurophysiological foundations of loss and failure sadness differently modulate emotional conceptual processing

Sadness is divided into two subtypes, namely loss and failure sadness, which are encoded by different concepts of one's mind. However, it is unclear how such a conceptual difference is supported by neurophysiological foundations. In the present study, we conducted an electroencephalogram experiment for processing congruency between loss- and failure-sadness contexts and emotional words. Electroencephalogram recordings were performed for 23 participants, using a picture-word priming paradigm without explicit congruency judgment. One of the three types of emotional pictures (loss, failure, or neutral picture as the baseline) preceded emotional target words with high, middle, or low fitting properties for sadness contexts in each trial. No significant word-onset event-related potential effects were observed. Upon word-offset event-related potential effects, middle-phase negative potentials around 400 ms for high-fitting words, increased in the failure prime-target context but not in the loss context, compared to the neutral context. Additionally, the negative potentials increased as the failure-sadness intensity decreased, which indicated contextual conflict between prime pictures and target words. In contrast, the corresponding negative potentials for the loss context increased as the loss-sadness intensity increased, which indicated congruency effects under sadness bias. In later latency, after around 400 ms, the slow negative event-related potential effects appeared similar for both the loss and failure contexts. These results suggest that loss and failure sadness are differently represented in the mind, and are founded on the middle-phase neurophysiological processing.

Residential Mobility Decreases Neural Responses to Social Norm Violation

Social norms are essential, but they vary across cultures and societies. With the internationalization of human society, population mobility has greatly increased, especially in developing countries, which can have an impact on people’s psychological states and behaviors and result in sociocultural change. The current research used three studies to examine the hypothesis that residential mobility plays a crucial role in the perception of social norm violations. Study 1 used an association test and found that residential mobility was correlated with the perception of both weak and strong social norm violations in females. Study 2 combined electroencephalography and found a negative differential N400 between weak social norm violations and appropriate behavior between residentially mobile and stable mindsets, suggesting that residential mobility modulates individuals’ detection of social norm-violating behavior. Study 3 revealed that residential mobility does not have a similar effect on semantic violations, which indicates that the effect of residential mobility does not occur in non-social norm violations. Our findings provide insight into how and why individuals’ detection of social norm-violating behaviors varies according to the dynamic development of society. As residential mobility continues to increase worldwide, especially in developing countries, more attention should be paid to the concomitant impact during the course of sociocultural change to build a better strategy for cultural specific social governance.

Does response modality influence conflict? Modelling vocal and manual response Stroop interference

In the Stroop task, color words are presented in colored fonts and the task of the subject is to either name the word or name the color. If the word and font color are in agreement, then the stimulus is said to be congruent (e.g., RED in red font color); however, if the word and font color are not in agreement, the stimulus is said to be incongruent (e.g., RED in blue font color). Conflict in the Stroop task is measured by both RT and accuracy. In prior research, the amount of conflict differs depending on the response modality, vocal versus manual. We applied a model for multichoice decision-making (and confidence), the RTCON2 model (Ratcliff & Starns, 2013) to the data from 4 experiments, 2 with 2-choice manual responses, 1 with 4-choice manual touch screen responses, 1 with both 4-choice vocal responses, and 4-choice manual keyboard responses. Changes in the rate of information accumulation captured conflict effects for the manual-response versions, but not for the vocal-response version. Adding an extra nondecision time parameter allowed RTCON2 to account for the data patterns in the vocal-response version. However, to fully understand conflict in the vocal-response Stroop task, a model of conflict processing in the vocal word production system must be developed that would explain the additional processing time in the nondecision time parameter. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

How do we process prices? Electrophysiological evidence of componential analysis

The aim of this study was to evaluate if the processing of prices (e.g., 8 euro) involves separate analysis of the digit (8) and the monetary category (euro). Event-related potentials (ERPs) were recorded when participants performed a price comparison task in which a pair of prices was presented and they selected the one with higher monetary value. There were compatible comparisons where the digit and the monetary category of one price were higher than those of the other price (e.g., 7 euro - 4 cent, 7 > 4 and euro > cent), and incompatible comparisons where the number of one price was larger but the monetary category smaller than those of the other price (e.g., 4 euro - 7 cent, 4 < 7 but euro > cent). Compatibility effect modulated ERPs in the 350-450 ms time window, with more negative amplitudes in incompatible trials relative to compatible trials. This pattern of results suggests that prices were processed in a componential manner, challenging the evidences of the holistic model. The results of this study agree with the general model framework for multi-symbol number comparison: The constituents of a multi-symbol magnitude are processed and compared to each other separately in a componential manner.

Absolute Pitch and Musical Expertise Modulate Neuro-Electric and Behavioral Responses in an Auditory Stroop Paradigm

Musicians have considerable experience naming pitch-classes with verbal (e.g., Doh, Ré, and Mi) and semiotic tags (e.g., musical notation). On the one end of the spectrum, musicians can identify the pitch of a piano tone or quality of a chord without a reference tone [i.e., absolute pitch (AP) or relative pitch], which suggests strong associations between the perceived pitch information and verbal labels. Here, we examined the strength of this association using auditory versions of the Stroop task while neuro-electric brain activity was measured using high-density electroencephalography. In separate blocks of trials, participants were presented with congruent or incongruent auditory words from English language (standard auditory Stroop), Romanic solemnization, or German key lexicons (the latter two versions require some knowledge of music notation). We hypothesized that musically trained groups would show greater Stroop interference effects when presented with incongruent musical notations than non-musicians. Analyses of behavioral data revealed small or even non-existent congruency effects in musicians for solfège and keycodes versions of the Stroop task. This finding was unexpected and appears inconsistent with the hypothesis that musical training and AP are associated with high strength response level associations between a perceived pitch and verbal label. The analyses of event-related potentials revealed three temporally distinct modulations associated with conflict processing. All three modulations were larger in the auditory word Stroop than in the other two versions of the Stroop task. Only AP musicians showed significant congruity effects around 450 and 750 ms post-stimulus when stimuli were presented as Germanic keycodes (i.e., C or G). This finding suggests that AP possessors may process alpha-numeric encodings as word forms with a semantic value, unlike their RP possessing counterparts and non-musically trained individuals. However, the strength of musical conditional associations may not exceed that of standard language in speech.

Theta oscillations show impaired interference detection in older adults during selective memory retrieval

Seemingly effortless tasks, such as recognizing faces and retrieving names, become harder as we age. Such difficulties may be due to the competition generated in memory by irrelevant information that comes to mind when trying to recall a specific face or name. It is unknown, however, whether age-related struggles in retrieving these representations stem from an inability to detect competition in the first place, or from being unable to suppress competing information once interference is detected. To investigate this, we used the retrieval practice paradigm, shown to elicit memory interference, while recording electrophysiological activity in young and older adults. In two experiments, young participants showed Retrieval-Induced Forgetting (RIF), reflecting the suppression of competing information, whereas older adults did not. Neurally, mid-frontal theta power (~4-8 Hz) during the first retrieval cycle, a proxy for interference detection, increased in young compared to older adults, indicating older adults were less capable of detecting interference. Moreover, while theta power was reduced across practice cycles in younger adults, a measure of interference resolution, older adults did not show such a reduction. Thus, in contrast with younger adults, the lack of an early interference detection signal rendered older adults unable to recruit memory selection mechanisms, eliminating RIF.

The Effects of Repeated Dyspnea Exposure on Response Inhibition

In order to treat dyspnea (=breathlessness) successfully, response inhibition (RI) as a major form of self-regulation is a premise. This is supported by research showing that self-regulation is associated with beneficial behavioral changes supporting treatment success in patients. Recent research showed that dyspnea has an impairing effect on RI, but the effects of repeated dyspnea exposure on RI remain unknown. Therefore, the present study tested the effects of repeated resistive load-induced dyspnea on RI over a 5-day period. Healthy volunteers (n = 34) performed the standard version of the Stroop task during baseline and dyspnea conditions on the first and fifth testing day and underwent an additional dyspnea exposure phase on each testing day. Variables of interest to investigate RI were reaction time, accuracy as well as the event-related potentials late positive complex (LPC) and N400 in the electroencephalogram. Reduced accuracy for incongruent compared to congruent stimuli during the dyspnea condition on the first testing day were found (p < 0.001). This was paralleled by a reduced LPC and an increased N400 for incongruent stimuli during the induction of dyspnea (p < 0.05). After undergoing dyspnea exposure, habituation of dyspnea intensity was evident. Importantly, on the fifth testing day, no differences between baseline, and dyspnea conditions were found for behavioral and electrophysiological measures of RI. These findings demonstrate that the impairing effect of dyspnea on RI disappeared after repeated dyspnea exposure in healthy participants. Translated to a clinical sample, it might cautiously be suggested that dyspnea exposure such as dyspnea perceived during physical exercise could reduce the impairing effect of dyspnea on RI which might have the potential to help increase self-regulation abilities and subsequent treatment efforts in dyspneic patients.

A fine-grained time course investigation of brain dynamics during conflict monitoring

The conflict monitoring model predicting higher anterior cingulate cortex (ACC) neuronal activity on incongruent trials has been recently challenged by a model predicting longer neuronal activity in incongruent trials characterized by longer RTs. To clarify this issue, brain dynamics were explored through event-related-potential (ERP) recordings during a Stroop task. We assessed differences between experimental conditions by combining complementary methods sensitive to the temporality of events including microstate, TANOVA and source localization analysis. The analysis demonstrated the same electrical dynamics only differed in duration towards the end of information processing in the incongruent condition. Specifically, the activation strength of the ACC region did not differ significantly between congruent and incongruent conditions but lasted longer in the incongruent condition. Taken together, our results support the model predicting longer neuronal activity in incongruent trials characterized by longer RTs. They highlight that brain dynamics can dramatically change through periods of interest and that caution is required when interpreting fMRI results. To conclude, these results indicate how time-sensitive measures can contribute to a better understanding of the mechanisms underlying information processing, and thus offer new venues to explore conflict monitoring.

Two Different Populations within the Healthy Elderly: Lack of Conflict Detection in Those at Risk of Cognitive Decline

During healthy aging, inhibitory processing is affected at the sensorial, perceptual, and cognitive levels. The assessment of event-related potentials (ERPs) during the Stroop task has been used to study age-related decline in the efficiency of inhibitory processes. Studies using ERPs have found that the P300 amplitude increases and the N500 amplitude is attenuated in healthy elderly adults compared to those in young adults. On the other hand, it has been reported that theta excess in resting EEG with eyes closed is a good predictor of cognitive decline during aging 7 years later, while a normal EEG increases the probability of not developing cognitive decline. The behavioral and ERP responses during a Counting-Stroop task were compared between 22 healthy elderly subjects with normal EEG (Normal-EEG group) and 22 healthy elderly subjects with an excess of EEG theta activity (Theta-EEG group). Behaviorally, the Normal-EEG group showed a higher behavioral interference effect than the Theta-EEG group. ERP patterns were different between the groups, and two facts are highlighted: (a) the P300 amplitude was higher in the Theta-EEG group, with both groups showing a P300 effect in almost all electrodes, and (b) the Theta-EEG group did not show an N500 effect. These results suggest that the diminishment in inhibitory control observed in the Theta-EEG group may be compensated by different processes in earlier stages, which would allow them to perform the task with similar efficiency to that of participants with a normal EEG. This study is the first to show that healthy elderly subjects with an excess of theta EEG activity not only are at risk of developing cognitive decline but already have a cognitive impairment.

N450 and LPC Event-Related Potential Correlates of an Emotional Stroop Task with Words Differing in Valence and Emotional Origin

Affective meaning of verbal stimuli was found to influence cognitive control as expressed in the Emotional Stroop Task (EST). Behavioral studies have shown that factors such as valence, arousal, and emotional origin of reaction to stimuli associated with words can lead to lengthening of reaction latencies in EST. Moreover, electrophysiological studies have revealed that affective meaning altered amplitude of some components of evoked potentials recorded during EST, and that this alteration correlated with the performance in EST. The emotional origin was defined as processing based on automatic vs. reflective mechanisms, that underlines formation of emotional reactions to words. The aim of the current study was to investigate, within the framework of EST, correlates of processing of words differing in valence and origin levels, but matched in arousal, concreteness, frequency of appearance and length. We found no behavioral differences in response latencies. When controlling for origin, we found no effects of valence. We found the effect of origin on ERP in two time windows: 290–570 and 570–800 ms. The earlier effect can be attributed to cognitive control while the latter is rather the manifestation of explicit processing of words. In each case, reflective originated stimuli evoked more positive amplitudes compared to automatic originated words.

Neurophysiological Evidence of Compensatory Brain Mechanisms Underlying Attentional-Related Processes in Symptomatically Remitted Patients with Schizophrenia

A recent electrophysiological study suggests existing compensatory brain activity as a mechanism for functional recovery of visual attention detection (the capacity for detecting external cues) in symptomatically remitted schizophrenia patients. Despite such evidence, little is known about other aspects of attentional-related processes in schizophrenia during clinical remission, such as their capacity to concentrate on the task at hands without being interfered by distracting information. To this end, we recorded event-related brain potentials (ERPs) from 20 symptomatically remitted schizophrenia patients and 20 healthy controls while they engaged in a classic Stroop task. Symptomatically remitted patients showed comparable Stroop interference to healthy controls, indicating a degree of functional recovery of such a capacity in these patients. On the neural level, the N450 over the fronto-central and central regions, a component of the ERPs related to conflict detection, was found across both groups, although patients presented a reduced N450 relative to healthy controls. By contrast, the amplitude of the sustained potential (SP) (600-800 ms) over the parieto-central and parietal regions, a component of the ERPs related to conflict resolution, was significantly increased in patients relative to healthy controls. Furthermore, such increased SP amplitude correlated positively with improved behavioral accuracy in symptomatically remitted patients with schizophrenia. These findings reveal that symptomatically remitted patients with schizophrenia increasingly recruited the parietal activity involving successful conflict resolution to offset reduced conflict detection. Therefore, this provides further insight into compensatory mechanisms potentially involving a degree of functional recovery of attentional-related processes in schizophrenia during clinical remission.

Neural cascade of conflict processing: Not just time-on-task

In visual conflict tasks (e.g., Stroop or flanker), response times (RTs) are generally longer on incongruent trials relative to congruent ones. Two event-related-potential (ERP) components classically associated with the processing of stimulus conflict are the fronto-central, incongruency-related negativity (N_inc) and the posterior late-positive complex (LPC), which are derived from the ERP difference waves for incongruent minus congruent trials. It has been questioned, however, whether these effects, or other neural measures of incongruency (e.g., fMRI responses in the anterior cingulate), reflect true conflict processing, or whether such effects derive mainly from differential time-on-task. To address this question, we leveraged high-temporal-resolution ERP measures of brain activity during two behavioral tasks. The first task, a modified Erikson flanker paradigm (with congruent and incongruent trials), was used to evoke the classic RT and ERP effects associated with conflict. The second was a non-conflict control task in which, participants visually discriminated a single stimulus (with easy and hard discrimination conditions). Behaviorally, the parameters were titrated to yield similar RT effects of conflict and difficulty (27ms). Neurally, both within-task contrasts showed an initial fronto-central negative-polarity wave (N2-latency effect), but they then diverged. In the difficulty difference wave, the initial negativity led directly into the posterior LPC, whereas in the incongruency contrast the initial negativity was followed a by a second fronto-central negative peak (N_inc), which was then followed by a considerably longer-latency LPC. These results provide clear evidence that the longer processing for incongruent stimulus inputs do not just reflect time-on-task or difficulty, but include a true conflict-processing component.

Event-Related Potentials and the Stroop Effect

In this manuscript, the researches on the Event-Related Potentials (ERP) elicited by the standard Stroop effect were reviewed. For the sake of clarity, only the parts of the manuscripts that reported the standard Stroop effect - ERPs relation were taken into consideration.

The Complex Pre-Execution Stage of Auditory Cognitive Control: ERPs Evidence from Stroop Tasks

Cognitive control has been extensively studied from Event-Related Potential (ERP) point of view in visual modality using Stroop paradigms. Little work has been done in auditory Stroop paradigms, and inconsistent conclusions have been reported, especially on the conflict detection stage of cognitive control. This study investigated the early ERP components in an auditory Stroop paradigm, during which participants were asked to identify the volume of spoken words and ignore the word meanings. A series of significant ERP components were revealed that distinguished incongruent and congruent trials: two declined negative polarity waves (the N1 and the N2) and three declined positive polarity wave (the P1, the P2 and the P3) over the fronto-central area for the incongruent trials. These early ERP components imply that both a perceptual stage and an identification stage exist in the auditory Stroop effect. A 3-stage cognitive control model was thus proposed for a more detailed description of the human cognitive control mechanism in the auditory Stroop tasks.

Moral Impression Management

Previous research revealed that emphasizing morality increases motivational processes that improve people’s task performance. Here we examined whether this emphasis differentially affects people’s performance in the presence of an in-group compared to an out-group member. Ostensibly while being evaluated by another person, participants performed an Implicit Association Test that was framed as a test of either their morality or their competence. Results showed a smaller bias toward Muslim women in the morality compared to the competence condition, but this effect was more pronounced when participants were evaluated by a member of their minimal in-group. Moreover, in that same condition, event-related potentials revealed increased perceptual attention (N1) and affected conflict and response monitoring (N450 and error-related negativity). These findings suggest that being moral is especially important when monitored by the in-group and reveal the cognitive processes associated with controlling intergroup bias in a social situation.

Age Differences in the Processing of Context Information

The dual mechanisms of control theory (DMC; Braver & Barch, 2002 ) assumes that age-related changes in the temporal structure of context processing underlie age differences in numerous cognitive control tasks. Younger adults usually exhibit a proactive control mode, characterized by cue-related context updating, while older adults show a reactive control mode, updating information when interference is detected. This study aimed at determining whether age differences in electrophysiological correlates of context updating in a pro-and reactive manner are independent of individual differences in task performance. To this end, younger and older adults were split into four groups according to their updating efficiency in behavioral data. Nineteen younger and 18 older adults completed a modified AX-Continuous-Performance Task ( Lenartowicz, Escobedo-Quiroz, & Cohen, 2010 ) in which correct responses to probes were either dependent (c-dep) or independent (c-indep) on a preceding contextual cue. Analysis of the behavioral data showed no differences in context updating when performance was matched, that is, between low performing younger and high performing older adults. However, low performing younger adults showed larger cue-locked parietal P3b amplitudes on c-dep than c-indep trials, indicating c-dep trials to require context updating to a larger extent, while high performing older adults exhibited a specific control strategy and continuously updated context information, as reflected in comparable P3b amplitudes on c-dep and c-indep trials. The persistent age effect in the P3b when controlling for performance differences suggests context updating to be fundamental to cognitive aging. High performing in contrast to low performing older adults also showed a larger negative N450 to ambiguous probes on c-dep trials associated with conflict detection. According to the DMC, this finding suggests late conflict detection at the time interference is detected, indicative of a reactive control style particular in high performing elderly.

Electrophysiological evidence for the involvement of the approximate number system in preschoolers' processing of spoken number words

Little is known about the neural underpinnings of number word comprehension in young children. Here we investigated the neural processing of these words during the crucial developmental window in which children learn their meanings and asked whether such processing relies on the Approximate Number System. ERPs were recorded as 3- to 5-year-old children heard the words one, two, three, or six while looking at pictures of 1, 2, 3, or 6 objects. The auditory number word was incongruent with the number of visual objects on half the trials and congruent on the other half. Children's number word comprehension predicted their ERP incongruency effects. Specifically, children with the least number word knowledge did not show any ERP incongruency effects, whereas those with intermediate and high number word knowledge showed an enhanced, negative polarity incongruency response (N(inc)) over centroparietal sites from 200 to 500 msec after the number word onset. This negativity was followed by an enhanced, positive polarity incongruency effect (P(inc)) that emerged bilaterally over parietal sites at about 700 msec. Moreover, children with the most number word knowledge showed ratio dependence in the P(inc) (larger for greater compared with smaller numerical mismatches), a hallmark of the Approximate Number System. Importantly, a similar modulation of the P(inc) from 700 to 800 msec was found in children with intermediate number word knowledge. These results provide the first neural correlates of spoken number word comprehension in preschoolers and are consistent with the view that children map number words onto approximate number representations before they fully master the verbal count list.

Evaluation of trait adjectives and ego pathology in schizophrenia: an N400 study

The N400, an event-related brain potential (ERP), can be triggered by semantic or arithmetic violations in visual or auditory stimulus material. Schizophrenia patients exhibit an altered N400 presumably resulting from impaired semantic memory associative networks. The present study investigates, whether an altered N400 can also be found in semantic violations of the own self-concept. We use simple descriptive sentences to combine semantics with the self-concept in order to explore differences and possible deficits in schizophrenia patients. Schizophrenia patients and controls were shown trait adjectives in reference to themselves. Participants had to decide if the presented trait adjective was congruent or incongruent with their own self-concept. Only in controls, the N400 was significantly more negative in the incongruent compared to the congruent condition. Controls seemed to profit from a stable self-concept as they were faster in judging if a given trait was descriptive for the self than for someone else, which might result from processes related to the self-reference effect. Interestingly, in schizophrenia patients, the higher the scores for ego pathology were, the smaller the N400 effect turned out to be. The diminished N400 effect is probably associated with a disturbed self-concept in schizophrenia.

The taste-visual cross-modal Stroop effect: An event-related brain potential study

Event-related potentials (ERPs) were recorded to explore, for the first time, the electrophysiological correlates of the taste-visual cross-modal Stroop effect. Eighteen healthy participants were presented with a taste stimulus and a food image, and asked to categorize the image as "sweet" or "sour" by pressing the relevant button as quickly as possible. Accurate categorization of the image was faster when it was presented with a congruent taste stimulus (e.g., sour taste/image of lemon) than with an incongruent one (e.g., sour taste/image of ice cream). ERP analyses revealed a negative difference component (ND430-620) between 430 and 620ms in the taste-visual cross-modal Stroop interference. Dipole source analysis of the difference wave (incongruent minus congruent) indicated that two generators localized in the prefrontal cortex and the parahippocampal gyrus contributed to this taste-visual cross-modal Stroop effect. This result suggests that the prefrontal cortex is associated with the process of conflict control in the taste-visual cross-modal Stroop effect. Also, we speculate that the parahippocampal gyrus is associated with the process of discordant information in the taste-visual cross-modal Stroop effect.

Moral concerns increase attention and response monitoring during IAT performance: ERP evidence

Previous research has revealed that people value morality as a more important person characteristic than competence. In this study, we tested whether people adjust their less explicit behavior more to moral than competence values. Participants performed an Implicit Association Test (IAT) that was either framed as a test of their morality or as a test of their competence. The behavioral results revealed a smaller IAT effect (i.e. a weaker negative implicit bias toward Muslims) in the morality condition than in the competence condition. Moreover, event-related potentials indicated increased social categorization of faces (as indexed by the N1 and P150) and enhanced conflict- and error monitoring (N450 and error-related negativity) in the morality condition compared to the competence condition. These findings indicate that an emphasis on morality can increase attentional and motivational processes that help to improve people's task performance.

Asymmetry in stimulus and response conflict processing across the adult lifespan: ERP and EMG evidence

Several studies have shown that conflict processing improves from childhood to adulthood and declines from adulthood to old age. However the neural mechanisms underlying this lifespan asymmetry were previously unexplored. We combined event-related potentials (ERPs) and electromyography (EMG) to examine lifespan changes in stimulus and response conflict processing using a modified Stroop task. We used a Stroop task that a priori dissociated stimulus and response conflict. Delayed P3b latency and increased amplitude revealed that middle age adults have a deficit in stimulus processing. Additionally a sustained P3a across frontal and central electrodes occurred only in middle age adults indicating the recruitment of frontal activity. Conversely, decreased lateralized readiness potential (LRP) amplitude and increased EMG activity in the incorrect hand in adolescents reveal protracted development of response processing into late adolescence. The N450, a measure of conflict processing, was found to be sensitive to both stimulus and response conflict. Altogether these results provide evidence for asymmetrical differences in stimulus and response conflict processing across adolescence, young adulthood and middle age.

An electrophysiological correlate of conflict processing in an auditory spatial Stroop task: the effect of individual differences in navigational style

Recent work has identified an event-related potential (ERP) component, the incongruency negativity (N(inc)), which is sensitive to auditory Stroop conflict processing. Here, we investigated how this index of conflict processing is influenced by individual differences in cognitive style. There is evidence that individuals differ in the strategy they use to navigate through the environment; some use a predominantly verbal-egocentric strategy while others rely more heavily on a spatial-allocentric strategy. In addition, navigational strategy, assessed by a way-finding questionnaire, is predictive of performance on an auditory spatial Stroop task, in which either the semantic or spatial dimension of stimuli must be ignored. To explore the influence of individual differences in navigational style on conflict processing, participants took part in an auditory spatial Stroop task while the electroencephalogram (EEG) was recorded. Whereas behavioral performance only showed a main effect of congruency, we observed the predicted three-way interaction between congruency, task type and navigational style with respect to our physiological measure of Stroop conflict. Specifically, congruency-dependent modulation of the N(inc) was observed only when participants performed their non-dominant task (e.g., verbal navigators attempting to ignore semantic information). These results confirm that the N(inc) reliably indexes auditory Stroop conflict and extend previous results by demonstrating that the N(inc) is predictably modulated by individual differences in cognitive style.

A computerized stroop test for the evaluation of psychotropic drugs in healthy participants

BACKGROUND

The Stroop paradigm evaluates susceptibility to interference and is sensitive to dysfunction in frontal lobes and drug effects. The aim of the present study was to establish a simple and reliable computerized version of Stroop color-word test, which can be used for screening of various psychotropic drugs.

MATERIALS AND METHODS

The standardized method was followed in all cases, by recording the reaction time (RT) in msec in 24 healthy participants using computerized version of Stroop color-word test. Reproducibility of the test procedure was evaluated by recording the RTs by a single experimenter on two sessions (interday reproducibility). Validity of the model was further tested by evaluating the psychotropic effect of Zolpidem 5 mg, Caffeine 500 mg, or Placebo on 24 healthy subjects in a randomized, double blind three-way crossover design.

RESULTS

The method was found to produce low variability with coefficient of variation less than 10%. Interday reproducibility was very good as shown by Bland-Altman plot with most of the values within ±2SD. There was a significant increase in RTs in Stroop performance with Zolpidem at 1 hr and 2 hrs; in contrast, caffeine significantly decreased RTs in Stroop performance at 1 hr only compared to placebo.

CONCLUSION

The Stroop color-word recording and analysis system is simple, sensitive to centrally acting drug effects, and has potential for future experimental psychomotor assessment studies.

Semantic Conflict Processing in the Color-Word Stroop and the Emotional Stroop

With the aim of establishing the temporal locus of the semantic conflict in color-word Stroop and emotional Stroop phenomena, we analyzed the Event-Related Potentials (ERPs) elicited by nonwords, incongruent and congruent color words, colored words with positive and negative emotional valence, and colored words with neutral valence. The incongruent, positive, negative, and neutral stimuli produced interference in the behavioral response to the color of the stimuli. The P150/N170 amplitude was sensitive to the semantic equivalence of both dimensions of the congruent color words. The P3b amplitude was smaller in response to incongruent color words and to positive, negative, and neutral colored words than in response to the congruent color words and colored nonwords. There were no differences in the ERPs induced in response to colored words with positive, negative, and neutral valence. Therefore, the P3b amplitude was sensitive to interference from the semantic content of the incongruent, positive, negative, and neutral words in the color-response task, independently of the emotional content of the colored words. In addition, the P3b amplitude was smaller in response to colored words with positive, negative, and neutral valence than in response to the incongruent color words. Overall, these data indicate that the temporal locus of the semantic conflict generated by the incongruent color words (in the color-word Stroop task) and by colored words with positive, negative, and neutral valence (in the emotional Stroop task) appears to occur in the range 300–450 ms post-stimulus.

On the interaction between sad mood and cognitive control: the effect of induced sadness on electrophysiological modulations underlying Stroop conflict processing

The present study employed high-density ERPs to examine the effect of induced sad mood on the spatiotemporal correlates of conflict monitoring and resolution in a colour-word Stroop interference task. Neuroimaging evidence and dipole modelling implicates the involvement of the anterior cingulate cortex (ACC) and medial prefrontal cortex (mPFC) regions in conflict-laden interference control. On the basis that these structures have been found to mediate emotion-cognition interactions in negative mood states, it was predicted that Stroop-related cognitive control, which relies heavily on anterior neural sources, would be affected by effective sad mood provocation. Healthy participants (N=14) were induced into transient sadness via use of autobiographical sad scripts, a well-validated mood induction technique (Liotti et al., 2000a, 2002). In accord with previous research, interference effects were shown at both baseline and sad states while Stroop conflict was associated with early (N450) and late (Late Positive Component; LPC) electrophysiological modulations at both states. Sad mood induction attenuated the N450 effect in line with our expectation that it would be susceptible to modulation by mood, given its purported anterior limbic source. The LPC effect was displayed at the typical posterior lateral sites but, as predicted, was not affected by sad mood. However, frontocentral LPC activity-presumably generated from an additional anterior limbic source-was affected at sad state, hinting a role in conflict monitoring. Although the neurophysiological underpinnings of interference control are yet to be clarified, this study provided further insight into emotion-cognition interactions as indexed by Stroop conflict-laden processing.

The Met-genotype of the BDNF Val66Met polymorphism is associated with reduced Stroop interference in elderly

Aging is accompanied by impairments of executive functions that rely on the functional integrity of fronto-striatal networks. This integrity is modulated by the release of neurotrophins like the brain-derived-neurotrophic factor (BDNF). Here, we investigate effects of the functional BDNF Val66Met polymorphism on interference processing in 131 healthy elderly subjects using event-related potentials (ERPs). In a Stroop task, participants had to indicate the name or the colour of colour-words while colour was either compatible or incompatible with the name. We show that susceptibility to Stroop-interference is affected by the BDNF Val66Met polymorphism: the Met-allele carriers showed better performance and enhanced N450 in interference trials. Other processes necessary to prepare and allocate cognitive resources to a particular task were not affected by BDNF Val66Met polymorphism, underlining the specificity of the observed effects. The observed performance and ERP difference is possibly due to dopamine related effects of BDNF in fronto-striatal networks, where it putatively mediates a shift in the balance of the direct and indirect pathway involved in inhibitory functions.

The Nature of Affective Priming in Music and Speech

The phenomenon of affective priming has caught scientific interest for over 30 years, yet the nature of the affective priming effect remains elusive. This study investigated the underlying mechanism of cross-modal affective priming and the influence of affective incongruence in music and speech on negativities in the N400 time-window. In Experiment 1, participants judged the valence of affective targets (affective categorization). We found that music and speech targets were evaluated faster when preceded by affectively congruent visual word primes, and vice versa. This affective priming effect was accompanied by a significantly larger N400-like effect following incongruent targets. In this experiment, both spreading of activation and response competition could underlie the affective priming effect. In Experiment 2, participants categorized the same affective targets based on nonaffective characteristics. However, as prime valence was irrelevant to the response dimension, affective priming effects could no longer be attributable to response competition. In Experiment 2, affective priming effects were observed neither at the behavioral nor electrophysiological level. The results of this study indicate that both affective music and speech prosody can prime the processing of visual words with emotional connotations, and vice versa. Affective incongruence seems to be associated with N400-like effects during evaluative categorization. The present data further suggest a role of response competition during the affective categorization of music, prosody, and words with emotional connotations.

Cognitive and electrophysiological correlates of the bilingual stroop effect

The color word Stroop effect in bilinguals is commonly half the magnitude when the written and naming languages are different (between) than when they are the same (within). This between-within language Stroop difference (BWLS) is likened to a response set effect, with greater response conflict for response relevant than irrelevant words. The nature of the BWLS was examined using a bilingual Stroop task. In a given block (Experiment 1), color congruent and incongruent words appeared in the naming language or not (single), or randomly in both languages (mixed). The BWLS effect was present for both balanced and unbalanced bilinguals, but only partially supported a response set explanation. As expected, color incongruent trials during single language blocks, lead to slower response times within than between languages. However, color congruent trials during mixed language blocks led to slower times between than within languages, indicating that response-irrelevant stimuli interfered with processing. In Experiment 2, to investigate the neural timing of the BWLS effect, event related potentials were recorded while balanced bilinguals named silently within and between languages. Replicating monolingual findings, an N450 effect was observed with larger negative amplitude for color incongruent than congruent trials (350-550 ms post-stimulus onset). This effect was equivalent within and between languages, indicating that color words from both languages created response conflict, contrary to a strict response set effect. A sustained negativity (SN) followed with larger amplitude for color incongruent than congruent trials, resolving earlier for between than within language Stroop. This effect shared timing (550-700 ms), but not morphology or scalp distribution with the commonly reported sustained potential. Finally, larger negative amplitude (200-350 ms) was observed between than within languages independent of color congruence. This negativity, likened to a no-go N2, may reflect processes of inhibitory control that facilitate the resolution of conflict at the SN, while the N450 reflects parallel processing of distracter words, independent of response set (or language). In sum, the BWLS reflects brain activity over time with contributions from language and color conflict at different points.

Strategic allocation of attention reduces temporally predictable stimulus conflict

Humans are able to continuously monitor environmental situations and adjust their behavioral strategies to optimize performance. Here we investigate the behavioral and brain adjustments that occur when conflicting stimulus elements are, or are not, temporally predictable. ERPs were collected while manual response variants of the Stroop task were performed in which the SOAs between the relevant color and irrelevant word stimulus components were either randomly intermixed or held constant within each experimental run. Results indicated that the size of both the neural and behavioral effects of stimulus incongruency varied with the temporal arrangement of the stimulus components, such that the random-SOA arrangements produced the greatest incongruency effects at the earliest irrelevant first SOA (-200 msec) and the constant-SOA arrangements produced the greatest effects with simultaneous presentation. These differences in conflict processing were accompanied by rapid (∼150 msec) modulations of the sensory ERPs to the irrelevant distractor components when they occurred consistently first. These effects suggest that individuals are able to strategically allocate attention in time to mitigate the influence of a temporally predictable distractor. As these adjustments are instantiated by the participants without instruction, they reveal a form of rapid strategic learning for dealing with temporally predictable stimulus incongruency.

Event-Related Oscillations in Alcoholism Research: A Review

Alcohol dependence is characterized as a multi-factorial disorder caused by a complex interaction between genetic and environmental liabilities across development. A variety of neurocognitive deficits/dysfunctions involving impairments in different brain regions and/or neural circuitries have been associated with chronic alcoholism, as well as with a predisposition to develop alcoholism. Several neurobiological and neurobehavioral approaches and methods of analyses have been used to understand the nature of these neurocognitive impairments/deficits in alcoholism. In the present review, we have examined relatively novel methods of analyses of the brain signals that are collectively referred to as event-related oscillations (EROs) and show promise to further our understanding of human brain dynamics while performing various tasks. These new measures of dynamic brain processes have exquisite temporal resolution and allow the study of neural networks underlying responses to sensory and cognitive events, thus providing a closer link to the physiology underlying them. Here, we have reviewed EROs in the study of alcoholism, their usefulness in understanding dynamical brain functions/dysfunctions associated with alcoholism as well as their utility as effective endophenotypes to identify and understand genes associated with both brain oscillations and alcoholism.

Auditory conflict processing in ADHD

BACKGROUND

Impaired cognitive control has been implicated as an important developmental pathway to attention deficit/hyperactivity disorder (ADHD). Cognitive control is crucial to suppress interference resulting from conflicting information and can be measured by Stroop-like tasks. This study was conducted to gain insight into conflict processing in children with ADHD.

METHODS

Event-related potentials (ERPs) were recorded in an auditory Stroop task. Twenty-four children with ADHD were compared with 24 control children (aged 8-12 years).

RESULTS

No deficit in interference control was found on the auditory Stroop task in children with ADHD. Children with ADHD responded more slowly, less accurately and more variably compared to controls. No differences between the groups occurred in the early conflict-related ERPs. However, the difference between the congruent and the incongruent condition in the 450-550 ms time window was absent in the ADHD group compared to controls. In addition, the conflict sustained potential was found frontally in the ADHD group but parietally in the control group.

CONCLUSIONS

These ERP findings suggest that children with ADHD evaluate conflict to a lesser extent and differ in the way their brains select appropriate responses during conflict compared with controls.

Pupillary Stroop effects

We recorded the pupil diameters of participants performing the words' color-naming Stroop task (i.e., naming the color of a word that names a color). Non-color words were used as baseline to firmly establish the effects of semantic relatedness induced by color word distractors. We replicated the classic Stroop effects of color congruency and color incongruency with pupillary diameter recordings: relative to non-color words, pupil diameters increased for color distractors that differed from color responses, while they reduced for color distractors that were identical to color responses. Analyses of the time courses of pupil responses revealed further differences between color-congruent and color-incongruent distractors, with the latter inducing a steep increase of pupil size and the former a relatively lower increase. Consistent with previous findings that have demonstrated that pupil size increases as task demands rise, the present results indicate that pupillometry is a robust measure of Stroop interference, and it represents a valuable addition to the cognitive scientist's toolbox.