Age differences in attentional control: an event-related potential approach

We examined age differences in event-related potentials (ERPs) associated with attentional control of task-set selection and response interference by means of a cue-based switching paradigm in which participants performed the color or word Stroop task. The results of ERPs in the cue interval indicated that P3 latencies were slowed for older adults, suggesting age-related slowing in updating currently relevant task sets. Older adults also showed a larger CNV under switching than nonswitching conditions, indicating age differences in maintaining task sets over longer periods of time. The results of target-locked ERPs revealed a negativity to incompatible Stroop trials (Ni) that was prolonged for older adults, suggesting age differences in early conflict processing. Response-locked ERPs showed a negative deflection to incompatible Stroop trials (CRN) only for younger adults, suggesting age differences also in response-related conflict processing.     

Strategic control and medial frontal negativity: beyond errors and response conflict

Errors in timed choice tasks typically produce an error-related negativity (ERN) in the event-related potential (ERP). The error specificity of the ERN has been challenged by studies showing a correct response negativity (CRN). Forty-five participants engaged in a flanker task in which both compatibility between flankers and target and the probability of compatible flankers were manipulated. Correct responses elicited a CRN, the amplitude of which increased with the degree of mismatch between the presence of conflict and conflict probability, even on low-conflict (compatible) trials. The fronto-central N2 component was larger on high-conflict (incompatible) correct response trials. However, in contrast to some recent accounts, this N2 was largest for highly probable stimuli. These findings suggest revision to models of the effects of conflict on response-related negativity to account for strategic adjustments made in preparation for the response.     

Complementary modulation of N2 and CRN by conflict frequency

The present study investigated the modulation of the N2 and the correct‐related negativity (CRN) by conflict frequency. Conflict costs, as measured by reaction times and error rate, were reduced with increasing conflict frequency, indicating improved conflict resolution. N2 amplitudes in incompatible trials increased with higher conflict frequency, while postresponse CRN amplitudes decreased. In concert with behavioral findings of reduced conflict costs and greater interference suppression, the increase of N2 might reflect enhanced conflict resolution during stimulus processing. The CRN, however, might reflect postresponse implementation of cognitive control, which is reduced when conflict is already adequately resolved during stimulus processing. Furthermore, N2 and CRN in incompatible trials were inversely related on the between‐ and within‐subject level, implying that the two modes of implementing cognitive control are applied complementarily.     

Emotional interference under low versus high executive control

Previous research has demonstrated that task‐irrelevant emotional distractors interfere with task performance especially under low phasic executive control (i.e., in nonconflict trials). In the present study, we measured medio‐frontal ERPs (N2 and correct‐related negativity, CRN) to elucidate which aspects of task performance are affected by emotional interference in a flanker task. To create emotional interference, negative and neutral pictures were presented during the flanker stimuli. N2 and CRN were reduced after negative pictures, indicating that conflict processing and performance monitoring are both affected by emotional interference. On the behavioral level, prolonged response times after negative pictures were observed under low phasic executive control (i.e., in compatible trials). Additionally, we explored whether emotional interference is modulated not only by phasic changes in executive control (i.e., conflict vs. nonconflict trials) but also by tonic changes in executive control (i.e., low vs. high overall conflict frequency). To this end, the flanker task consisted of two blocks with 25% versus 75% incompatible trials. Prolonged response times after negative pictures in compatible trials were observed only under low tonic executive control but not under high executive control.     

Developmental Trajectories of Neural Mechanisms Supporting Conflict and Error Processing in Middle Childhood

To study age-related changes in cognitive control, event-related potentials (ERPs) of children aged 6–9 years, 10–12 years, and young adults were recorded during a Flanker task. Younger children were more susceptible to conflict than older ones and adults. The N2 in incongruent trials was smaller in younger than older children, who did not differ from adults. The error-related negativity (ERN) following errors, however, was larger in adults than in children, but did not differ between younger and older children. Delayed development of neural responses to error processing relative to conflict monitoring may indicate dissociable maturational time tables of subdivisions of the anterior cingulate cortex.     

Developmental trajectories of neural mechanisms supporting conflict and error processing in middle childhood

To study age-related changes in cognitive control, event-related potentials (ERPs) of children aged 6-9 years, 10-12 years, and young adults were recorded during a Flanker task. Younger children were more susceptible to conflict than older ones and adults. The N2 in incongruent trials was smaller in younger than older children, who did not differ from adults. The error-related negativity (ERN) following errors, however, was larger in adults than in children, but did not differ between younger and older children. Delayed development of neural responses to error processing relative to conflict monitoring may indicate dissociable maturational time tables of subdivisions of the anterior cingulate cortex.     

Development of response-monitoring ERPs in 7- to 25-year-olds

In a target discrimination task, trials with incorrect responses elicit event-related potentials (ERPs) that include an error-related negativity (ERN or Ne) and a later error-positivity (Pe). Substantial evidence points to the anterior cingulate cortex as the source generator of the ERN. We examined the development of ERP component morphology, amplitude and latency to processing of correct and incorrect responses in 124 children, 7 to 18 years of age, and 27 adults, 19 through 25 years of age. The ERN and Pe were recorded during a standard 480-trial visual flanker task. As expected, response times decreased significantly with age. The ERN amplitude in error trials increased with age, although this was qualified by a nonlinear change as well. The Pe amplitude did not change with age. In correct trials, most participants produced a small negativity corresponding to the timing of the ERN in error trials. This correct-response negativity (CRN) amplitude was larger in children than in adults. Results are discussed with respect to continued maturation of the anterior cingulate cortex and prefrontal cortex into young adulthood.     

Aging, probabilistic learning and performance monitoring

This study examined age-related alterations in electrocortical indices of performance monitoring in a probabilistic learning situation. The results showed differences between younger and older adults in the modulation of response- and feedback-related negativities by feedback validity. In younger adults, the error-related negativity/error negativity (ERN/Ne) was larger than the correct response-related negativity (CRN) in the high and medium feedback validity condition, whereas the feedback-related negativity (FRN) differentiated between positive and negative feedback in the low feedback validity condition. In older adults, amplitudes of the ERN/Ne and the CRN were dissociated only in the high feedback validity condition and the FRN did not differ between positive and negative feedback. This finding might suggest that performance monitoring is more prone to interference by probabilistic information in older adults. Further, the salience of negative feedback seems reduced with age.     

Changes of performance monitoring with learning in older and younger adults

This study examined age differences in performance monitoring during learning of a stimulus-response association task. At the beginning of the learning process, amplitudes of the response-locked error-related negativity (ERN or Ne) and correct response-related negativity (CRN) did not differ in both age groups. With advanced learning the response ERN/Ne increased and the CRN decreased in younger adults, but did not dissociate in older adults. Feedback ERN amplitudes decreased with learning in both age groups and were reduced in older relative to younger adults. Results indicate that performance monitoring became error specific with advanced learning in younger adults, but not in older adults. This might be due to weak representations of stimulus-response mappings in older adults as they learned worse. The decrease of the feedback ERN with learning and aging might suggest a decline of attention paid to negative feedback.     

On why not to rush older adults—relying on reactive cognitive control can effectively reduce errors at the expense of slowed responses

According to the dual‐mechanisms of cognitive control framework (DMC), older adults rely predominantly on reactive as opposed to proactive control. As a result, we expected elevated response conflict for older relative to younger adults with increasing task difficulty. Response‐locked ERP activity was examined separately for fast and slow responses (representing proactive and reactive control, respectively) at low, medium, and high levels of difficulty. Older adults recruited reactive control more often than the young, as reflected by increased behavioral costs and enhanced pre‐response negativity (PRN). No age differences in conflict detection (medial frontal negativity, MFN) were evident at low levels of difficulty, but response conflict increased along with difficulty for older adults. These data provide empirical support for the DMC suggesting that aging is associated with a less efficient reactive‐control mode of processing.     

Behavioural and electrophysiological measures of task switching during single and mixed-task conditions

In order to understand how the brain prepares for and executes a switch in task demand, we measured reaction time (RT), accuracy, and event-related brain potentials associated with performance in single and mixed-task blocks using a cued design. Our results show that trials which repeat in a mixed-task block (repeat trials) were more demanding than trials which repeated in a single-task block, as reflected by the presence of a RT mixing cost and by the presence of a smaller target-locked positivity (P3b) on repeat trials. Within a mixed-task block, repeat and switch trials also differed, where repeat trials showed evidence of greater preparation (larger cue-locked negativity), more efficient target processing (larger target-locked P3b), and shorter RTs. In addition, the cue-locked negativity difference remained despite equating repeat and switch trials on RT, suggesting that this negativity difference is specific to the switching process. Our results are discussed in light of existing models of task switching.     

Medial frontal negativities predict performance improvements during motor sequence but not motor adaptation learning

Alterations in our environment require us to learn or alter motor skills to remain efficient. Also, damage or injury may require the relearning of motor skills. Two types have been identified: movement adaptation and motor sequence learning. Doyon et al. (2003, Distinct contribution of the cortico‐striatal and cortico‐cerebellar systems to motor skill learning. Neuropsychologia, 41(3), 252‐262) proposed a model to explain the neural mechanisms related to adaptation (cortico‐cerebellar) and motor sequence learning (cortico‐striatum) tasks. We hypothesized that medial frontal negativities (MFNs), event‐related electrocortical responses including the error‐related negativity (ERN) and correct‐response‐related negativity (CRN), would be trait biomarkers for skill in motor sequence learning due to their relationship with striatal neural generators in a network involving the anterior cingulate and possibly the supplementary motor area. We examined 36 participants' improvement in a motor adaptation and a motor sequence learning task and measured MFNs elicited in a separate Spatial Stroop (conflict) task. We found both ERN and CRN strongly predicted performance improvement in the sequential motor task but not in the adaptation task, supporting this aspect of the Doyon model. Interestingly, the CRN accounted for additional unique variance over the variance shared with the ERN suggesting an expansion of the model.     

Modulation of the error-related negativity by response conflict

An arrow version of the Eriksen flanker task was employed to investigate the influence of conflict on the error-related negativity (ERN). The degree of conflict was modulated by varying the distance between flankers and the target arrow (CLOSE and FAR conditions). Error rates and reaction time data from a behavioral experiment were used to adapt a connectionist model of this task. This model was based on the conflict monitoring theory and simulated behavioral and event-related potential data. The computational model predicted an increased ERN amplitude in FAR incompatible (the low-conflict condition) compared to CLOSE incompatible errors (the high-conflict condition). A subsequent ERP experiment confirmed the model predictions. The computational model explains this finding with larger postresponse conflict in far trials. In addition, data and model predictions of the N2 and the LRP support the conflict interpretation of the ERN.     

Age-related alterations in performance monitoring during and after learning

Changes of performance monitoring during and after learning of stimulus-response (S-R) associations were examined in younger and older adults using event-related brain potentials (ERPs). To determine whether age-related differences in performance monitoring are attenuated when learning performance is equalized between age groups, participants learned S-R associations until they reached a learning criterion. After completed learning, time pressure was introduced to assess whether time pressure pronounces age-related differences in performance monitoring. In the initial learning phase, performance monitoring was unspecific, indicated by similar-sized ERN/Ne (error-related/error negativity) and CRN (correct response-related negativity) amplitudes. With advanced learning, ERN/Ne and CRN amplitudes dissociated in younger participants, suggesting error-specific performance monitoring, whereas in older participants, performance monitoring remained unspecific. However, after completed learning and under time pressure, larger ERN/Ne than CRN amplitudes were observed in older participants, too. This finding suggests that error-specific performance monitoring develops with learning in younger, but not necessarily in older adults. The administration of time pressure seemed to force older adults to monitor error responses more specifically.     

大脑对早期、晚期冲突信息处理的事件相关电位研究

目的:进一步了解大脑处理冲突信息的机制。方法:采用脑事件相关电位(ERP)技术, 用经典的Flanker作业刺激范式组成的成对刺激作为视觉刺激,并通过低分辨率电磁地形图(LORETA) 技术,对16例健康正常受试者进行测检。结果:无论是失匹配状态、不一致Flanker作业,还是二者兼而有之,均可引出一负波。该冲突性负波主要分布在前、中头部。LORETA源定位分析显示该负波可能源于前额叶皮层、扣带回。结论:大脑存在一个探测及处理冲突信息的系统。该系统处理各种冲突信息,可能位于前额叶皮层、扣带回附近。     

Event-related potential correlates of task switching and switch costs

Studies of task switching demonstrate that task switches are associated with response costs and that these costs are reduced when a cue is presented in advance of a switch. The present study examined cortical event-related potential correlates of task switching and switch costs in 39 participants during a cued match/mismatch discrimination task. Compared with non-switch trials, switch trials were associated with a larger cue-related, anticipatory P3b-like waveform. Switch trials were also associated with smaller target-related, stimulus-dependent P2 and P3-like components. Moreover, the switch-related amplitude variability in the P3b to the cue and the P2 to the target were associated with unique components of the residual switch costs. The results support an integrated model of task switching with complementary yet distinct roles for anticipatory and stimulus-dependent processes in task switching and switch costs.     

The effect of manipulating task difficulty on error-related negativity in individuals with obsessive-compulsive symptoms

Previous research has found that individuals with obsessive-compulsive (OC) symptoms show larger error-related negativity (ERN) and correct-response negativity (CRN) amplitudes than controls. Task difficulty was manipulated during a flanker task and a probabilistic learning task to determine the effect of difficulty on ERN and CRN amplitudes in those with high or low levels of OC symptoms. Increasing task difficulty during a flanker task attenuated ERN amplitudes and enhanced CRN amplitudes. Although larger ERN amplitudes were found in the high OC group compared to the low OC group during the easy flanker task, this group difference was no longer apparent during the difficult version of the flanker task. Increasing difficulty during the probabilistic learning task had no effect on group differences in ERN or CRN amplitudes. The results of this study suggest that the hyperactive error-monitoring activity associated with OC symptoms depends on the difficulty and type of task performed.     

Mental fatigue and task control: planning and preparation

The effects of mental fatigue on planning and preparation for future actions were examined, using a task switching paradigm. Fatigue was induced by "time on task," with subjects performing a switch task continuously for 2 hr. Subjects had to alternate between tasks on every second trial, so that a new task set was required on every second trial. Manipulations of response-stimulus intervals (RSIs) were used to examine whether subjects prepared themselves for the task change. Behavioral measurements, event-related potentials (ERPs), and mood questionnaires were used to assess the effects of mental fatigue. Reaction times (RTs) were faster on trials in which no change in task set was required in comparison with switch trials, requiring a new task set. Long RSIs were used efficiently to prepare for the processing of subsequent stimuli. With increasing mental fatigue, preparation processes seemed to become less adequate and the number of errors increased. A clear poststimulus parietal negativity was observed on repetition trials, which reduced with time on task. This attention-related component was less pronounced in switch trials; instead, ERPs elicited in switch trials showed a clear frontal negativity. This negativity was also diminished by time on task. ERP differences between repetition and switch trials became smaller with increasing time on task.     

Electrocortical and behavioral measures of response monitoring in young children during a Go/No-Go task

The current study examined behavioral measures and response‐locked event‐related brain potentials (ERPs) derived from a Go/No‐Go task in a large (N = 328) sample of 5‐ to 7‐year‐olds in order to better understand the early development of response monitoring and the impact of child age and sex. In particular, the error‐related negativity (ERN, defined on both error trials alone and the difference between error and correct trials, or ΔERN), correct response negativity (CRN), and error positivity (P_e) were examined. Overall, the ERN, CRN, and the P_e were spatially and temporally similar to those measured in adults and older children. Even within our narrow age range, older children were faster and more accurate; a more negative ΔERN and a more positive P_e were associated with: increasing age, increased accuracy, and faster reaction times on errors, suggesting these enhanced components reflected more efficient response monitoring of errors over development. Girls were slower and more accurate than boys, although both genders exhibited comparable ERPs. Younger children and girls were characterized by increased posterror slowing, although they did not demonstrate improved posterror accuracy. Posterror slowing was also related to a larger P_e and reduced posterror accuracy. Collectively, these data suggest that posterror slowing may be unrelated to cognitive control and may, like the P_e, reflect an orienting response to errors. © 2011 Wiley Periodicals, Inc. Dev Psychobiol 54:139‐150, 2012.     

Response-monitoring dysfunction in aging and Alzheimer's disease: an event-related potential study

Executive control is a broad-reaching function that includes response monitoring and is likely implemented in the frontal lobes. Age- and dementia-related changes in response-monitoring were assessed during a Picture-Name Verification Task, using response-synchronized event-related potential (ERP) markers of response monitoring: the centrally oriented error-related negativity (ERN); the smaller and more frontally-oriented correct-response negativity (CRN); and the positivity associated with errors (Pe), a marker of error awareness. These were recorded from 10 younger and 10 older healthy controls, as well as 12 Alzheimer's disease (AD) patients. Although the older and younger controls showed equivalent accuracy, error awareness (Pe), and relative ERN>CRN amplitude, aging was associated with slower behavioral responses and decreased ERN amplitude. Although dementia was associated with decreased accuracy, decreased ERN, and a loss of relative ERN>CRN amplitude, error awareness (Pe) remained somewhat intact in AD patients. In AD patients, CRN amplitude was affected by item certainty (assessed a week earlier), being larger to items that were idiosyncratically difficult for patients to name.