Peter E. Clayson

Conflict adaptation and sequential trial effects: support for the conflict monitoring theory.

The purpose of this study was to investigate the cognitive control process of conflict adaptation and the recruitment of cognitive control across sequential trials-termed higher-order trial effects-using the N2 and P3 components of the scalp-recorded event-related potential (ERP). High-density ERPs were obtained from 181 healthy individuals (93 female, 88 male) during a modified Eriksen flanker task. Behavioral measures (i.e., error rates, reaction times [RTs]) and N2 and P3 amplitudes showed reliable conflict adaptation (i.e., previous-trial congruencies influenced current-trial measures). Higher-order trial effects were quantified across multiple sequential presentations of congruent or incongruent trials (e.g., four consecutive incongruent trials). For higher-order trial effects, P3 amplitudes and RTs reliably decreased across both congruent and incongruent trials. Consistent with the conflict monitoring theory, N2 amplitudes decreased across incongruent trials and increased across congruent trials. N2 amplitudes were positively correlated with incongruent-trial RTs; no significant correlations were found for P3 amplitudes and RTs. Effects remained when stimulus-response repetitions were removed. Results indicate that RTs and ERP measures are sensitive to modulations of cognitive control associated with conflict across multiple congruent and incongruent trials. Implications for the conflict monitoring theory of cognitive control are discussed.

Effects of repetition priming on electrophysiological and behavioral indices of conflict adaptation and cognitive control

We investigated the effects of repetition priming on indices of conflict adaptation. Event-related potentials (ERPs) were obtained while 210 healthy individuals (111 female, 99 male) completed an Eriksen flanker task. Error rates, response times (RTs), and N2 and P3 amplitudes showed significant conflict adaptation (i.e., previous-trial congruencies influenced current-trial measures). After omitting trials with stimulus-response repetitions, RTs did not index conflict adaptation, but did show switching effects; error rates and N2 and P3 amplitudes remained sensitive to conflict adaptation. P3 amplitudes positively correlated with RTs. N2 amplitudes correlated with RTs only on incongruent trials following congruent trials after excluding repetitions. Results indicate that neural indices of conflict monitoring remain reliably associated with conflict adaptation effects in the absence of RT adjustments upon omission of repetition priming effects.

Sex differences in electrophysiological indices of conflict monitoring

The purpose of this study was to investigate sex differences in cognitive control as measured by the stimulus-locked N2 component of the event-related potential (ERP). High-density ERPs were obtained from 114 healthy individuals (60 females, 54 males) who completed a modified Eriksen Flanker Task. Behavioral measures (i.e., error rates, reaction times) and N2 amplitudes were analyzed. On the flanker task, females responded significantly slower and committed more errors than males. For N2 amplitude, there was a significant main effect of congruency, with increased amplitude to incongruent trials. Importantly, sexes differed as a function of congruency, with males showing significantly larger incongruent N2 amplitudes than females. Sex differences in N2 amplitude remained in a subgroup of participants that did not differ for behavioral, demographic, and affective variables. No sex differences were shown for electrophysiological or behavioral indices of conflict adaptation. Results indicate sex differences in brain activation associated with conflict monitoring. Findings may be explained by two contradictory possibilities: (1) females more effectively monitor conflict as indicated by less neural activation than males for similar behavioral performance in a matched subsample, or, (2) females less effectively monitor conflict than males.

Cognitive control in mild traumatic brain injury: Conflict monitoring and conflict adaptation

Recent studies suggest that individuals who have experienced a concussion or mild traumatic brain injury (TBI) show deficits in cognitive control. We tested the hypothesis that behavioral (response time [RT] and error rate) and electrophysiological (N450 and conflict SP components of the event-related potential [ERP]) reflections of conflict monitoring and conflict adaptation would be attenuated in 29 individuals with mild TBI compared to 36 control participants. Groups did not differ in age, sex, years of education, or neuropsychological test performance. Conflict monitoring and conflict adaptation can be seen when behavioral and ERP indices are reduced following high-conflict trials relative to low-conflict trials. Participants completed a Stroop task with 50% congruent and 50% incongruent trials. Behaviorally, both groups showed statistically significant conflict adaptation effects for RTs and error rates; these effects did not differ as a function of group. For ERPs, both groups showed more negative N450 and more positive conflict SP amplitudes on incongruent trials relative to congruent trials. Groups significantly differed in level of conflict adaptation for the conflict SP; controls showed significant conflict adaptation, whereas individuals with mild TBI did not. ERP amplitudes did not correlate with indices of injury severity or time since injury. Findings replicate and extend previous work that suggests the conflict SP is sensitive to conflict adaptation in healthy individuals, but is decreased in individuals across the range of TBI severity. Findings also suggest that mild TBI is associated with intact conflict monitoring, but altered conflict adaptation and adjustment processes.

The relationship between cognitive performance and electrophysiological indices of performance monitoring

Studies of electrophysiological indices of performance monitoring, such as the error-related negativity (ERN), posterror positivity (Pe), and N2 components of the event-related potential (ERP), suggest that increased ERN and Pe amplitudes and decreased N2 amplitudes are associated with better cognitive flexibility and cognitive control abilities; however, few studies have directly examined the relationship between cognitive performance and ERP indices of performance monitoring. We examined the neuropsychological profile of 89 healthy individuals who performed a modified flanker task. The neuropsychological domains tested included memory, verbal fluency, and attention/executive functioning. Pearson’s correlations and multiple regression analyses showed a significant relationship between measures of attention/executive functioning and ERN amplitude, even when negative affect, reaction time interference, and posterror slowing were controlled. N2 amplitude related only to posterror slowing. The amplitude of the Pe was not significantly related to any cognitive domains. These findings are consistent with recent work indicating that performance monitoring requires attention skills and cognitive flexibility. Implications for the conflict-monitoring and reinforcement-learning theories are discussed.

Sex differences in error-related performance monitoring.

We tested competing hypotheses for sex differences in performance monitoring using the error-related negativity and the posterror positivity components of the event-related potential (ERP). High-density ERPs were acquired while 100 female and 98 male partcipants completed a flanker task. Sexes did not differ in accuracy or posterror slowing, although females showed longer overall response times. Males showed increased amplitude error-related negativity and posterror positivity components relative to females; sexes did not differ on correct-trial ERPs. Sex differences remained in subgroups matched for depression and anxiety levels. Results indicate that participant sex should be considered in understanding the cognitive and emotional correlates of performance monitoring.

Performance monitoring following conflict: internal adjustments in cognitive control?

The purpose of this study was to investigate the effects of strategic conflict-related adjustments in cognitive control processes on indices of performance monitoring. Previous research has examined the ability of parametric task-related manipulations to bias attention to errors; however, the present study sought to elucidate the effects of internal adjustments in control mediated by the anterior cingulate cortex on error-related conflict processing. High-density event-related potentials (ERPs) were obtained from 124 healthy individuals (68 female, 66 male) during a modified Eriksen flanker task. Behavioral measures (i.e., error rates, response times [RTs]) and N2 amplitudes showed significant conflict adaptation (i.e., previous-trial congruencies influenced current-trial measures). For error trials, the error-related negativity (ERN) was more negative for errors on high-conflict (i.e., incongruent) trials following high-conflict trials relative to errors on high-conflict trials following low-conflict (i.e., congruent) trials. These findings indicate that error-related conflict-monitoring processes adjust according to the post-conflict recruitment of strategic cognitive control and suggest an ongoing interplay between conflict and internal adjustments in control resources. Interpretations from the perspective of the conflict monitoring theory of cognitive control, the reinforcement learning theory, and the response-outcome theory of the ERN are discussed.

Performance Monitoring and Cognitive Control in Individuals with Mild Traumatic Brain Injury

Literature suggests that individuals with mild traumatic brain injury (mTBI) show subtle abnormalities in the cognitive control process of performance monitoring. The neural bases of performance monitoring can be measured using the error-related negaitivity (ERN) and post-error positivity (Pe) components of the scalp-recorded event-related potential (ERP). Thirty-six individuals with mTBI and 46 demographically similar controls completed a modified color-naming Stroop task while ERPs were recorded. Separate repeated-measures analyses of variance were used to examine the behavioral (response times [RT] and error rates) and ERP (ERN and Pe amplitudes) indices of performance monitoring. Both groups showed slower RTs and increased error rates on incongruent trials relative to congruent trials. Likewise, both groups showed more negative ERN and more positive Pe amplitude to error trials relative to correct trials. Notably, there were no significant main effects or interactions of group for behavioral and ERP measures. Subgroup and correlational analyses with post-concussive symptoms and indices of injury severity were also not significant. Findings suggest comparable performance to non-injured individuals in some aspects of cognitive control in this sample. Neuropsychological implications and comparison with other cognitive control component processes in individuals with TBI are provided.

Cognitive Control and Conflict Adaptation Similarities in Children and Adults

Conflict adaptation effects occur when previous-trial congruency affects current-trial performance. We examined developmental differences in response time (RT), error rate, and electrophysiological (N450 and conflict slow-potential [conflict SP] event-related potentials [ERPs]) indices of conflict adaptation in 21 typically developing children and 26 adults during a Stroop task. Children exhibited significantly slower RTs, increased error rates, and increased ERP amplitudes relative to adults. Groups did not differ in magnitude of conflict adaptation for RTs, error rates, or the conflict SP. Neither group showed significant N450 conflict adaptation. Results suggest current indices of conflict adaptation do not differ between children and adults.

The effects of induced state negative affect on performance monitoring processes

Previous research suggests that performance-monitoring processes are related to personality traits; relationships with affective states, however, remain unclear. The purpose of this study was to replicate and extend previous findings that induced state negative affect alters electrophysiological reflections of performance monitoring. High-density event-related potentials (ERPs) were obtained from 69 healthy individuals (41 female, 28 male) who completed an Eriksen flanker task and received either encouraging or derogatory feedback based on mean reaction times (RTs) for 30-trial sub-blocks. Affective state, behavioral measures (i.e. error rates, RTs) and ERP measures [i.e. error-related negativity (ERN), post-error positivity (Pe) and N2] were assessed. Reaction times did not differ between feedback groups. Participants who received derogatory feedback committed more errors over time. Despite changes in affect, no significant group differences were demonstrated for behavioral or ERP measures of performance monitoring. Increases in vigilance were associated with more negative N2 amplitudes; no other changes in affective state were associated with changes in ERP measures. Results are consistent with findings suggesting performance-monitoring processes are only slightly affected by changes in affective state and fail to replicate previous studies suggesting the ERN is related to state changes in affect-supporting the possibility of the ERN as an endophenotype.