Ann Clawson

Making sense of all the conflict: a theoretical review and critique of conflict-related ERPs.

Cognitive control theory suggests that goal-directed behavior is governed by a dynamic interplay between areas of the prefrontal cortex. Critical to cognitive control is the detection and resolution of competing stimulus or response representations (i.e., conflict). Event-related potential (ERP) research provides a window into the nature and precise temporal sequence of conflict monitoring. We critically review the research on conflict-related ERPs, including the error-related negativity (ERN), Flanker N2, Stroop N450 and conflict slow potential (conflict SP or negative slow wave [NSW]), and provide an analysis of how these ERPs inform conflict monitoring theory. Overall, there is considerable evidence that amplitude of the ERN is sensitive to the degree of response conflict, consistent with a role in conflict monitoring. It remains unclear, however, to what degree contextual, individual, affective, and motivational factors influence ERN amplitudes and how ERN amplitudes are related to regulative changes in behavior. The Flanker N2, Stroop N450, and conflict SP ERPs represent distinct conflict-monitoring processes that reflect conflict detection (N2, N450) and conflict adjustment or resolution processes (N2, conflict SP). The investigation of conflict adaptation effects (i.e., sequence or sequential trial effects) shows that the N2 and conflict SP reflect post-conflict adjustments in cognitive control, but the N450 generally does not. Conflict-related ERP research provides a promising avenue for understanding the effects of individual differences on cognitive control processes in healthy, neurologic and psychiatric populations. Comparisons between the major conflict-related ERPs and suggestions for future studies to clarify the nature of conflict-related neural processes are provided.

Feedback and reward processing in high-functioning autism

Individuals with high-functioning autism often display deficits in social interactions and high-level cognitive functions. Such deficits may be influenced by poor ability to process feedback and rewards. The feedback-related negativity (FRN) is an event-related potential (ERP) that is more negative following losses than gains. We examined FRN amplitude in 25 individuals with Autism Spectrum Disorder (ASD) and 25 age- and IQ-matched typically developing control participants who completed a guessing task with monetary loss/gain feedback. Both groups demonstrated a robust FRN that was more negative to loss trials than gain trials; however, groups did not differ in FRN amplitude as a function of gain or loss trials. N1 and P300 amplitudes did not differentiate groups. FRN amplitude was positively correlated with age in individuals with ASD, but not measures of intelligence, anxiety, behavioral inhibition, or autism severity. Given previous findings of reduced-amplitude error-related negativity (ERN) in ASD, we propose that individuals with ASD may process external, concrete, feedback similar to typically developing individuals, but have difficulty with internal, more abstract, regulation of performance.

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.

Error processing in high-functioning Autism Spectrum Disorders.

Studies report error-processing abnormalities in high-functioning individuals with Autism Spectrum Disorders (ASD) that may be influenced by intelligence and autism severity. Error processing can be measured using the error-related negativity (ERN) and post-error positivity (Pe) components of the event-related potential (ERP), along with behavioral indices such as post-error reaction time (RT) slowing. We used a modified Flanker task to test the hypothesis that high-functioning individuals with ASD would show decreased amplitude ERN in 24 individuals with ASD and 21 age- and IQ-matched typically-developing control participants. Behaviorally, individuals with ASD committed more errors than controls, but groups did not significantly differ on RTs, although there was a trend-level difference in post-error slowing. For ERPs, ERN amplitude was significantly attenuated in individuals with ASD relative to controls; groups did not differ in Pe amplitude. Amplitude of the ERN was not significantly correlated with measures of intelligence, anxiety, behavioral inhibition, or general autism severity.

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.

Cognitive control adjustments and conflict adaptation in major depressive disorder.

Individuals with major depressive disorder (MDD) show alterations in the cognitive control function of conflict processing. We examined the influence of these deficits on behavioral and event-related potential (ERP) indices of conflict adaptation, a cognitive control process wherein previous-trial congruency modulates current-trial performance, in 55 individuals with MDD and 55 matched controls. ERPs were calculated while participants completed a modified flanker task. There were nonsignificant between-groups differences in response time, error rate, and N2 indices of conflict adaptation. Higher depressive symptom scores were associated with smaller mean N2 conflict adaptation scores for individuals with MDD and when collapsed across groups. Results were consistent when comorbidity and medications were analyzed. These findings suggest N2 conflict adaptation is associated with depressive symptoms rather than clinical diagnosis alone.

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.

Cognitive control and conflict adaptation in youth with high-functioning autism

BACKGROUND   Youth diagnosed with autism spectrum disorders (ASD) often show deficits in cognitive control processes, potentially contributing to characteristic difficulties monitoring and regulating behavior. Modification of performance following conflict can be measured by examining conflict adaptation, the adjustment of cognitive resources based on previous-trial conflict. The electrophysiological correlates of these processes can be measured using the N2, a stimulus-locked component of the event-related potential (ERP). METHODS   High-density ERPs and behavioral data [i.e. response times (RTs) and error rates] were acquired while 28 youth with ASD and 36 typically developing controls completed a modified Eriksen flanker task. RESULTS   Behaviorally, groups showed similar conflict adaptation effects; youth with ASD showed larger RT slowing on switch trials. For electrophysiology, controls demonstrated larger N2 amplitudes for incongruent (high-conflict) trials following congruent (low-conflict) trials than for incongruent trials following incongruent trials. Importantly, youth with ASD showed no such differences in N2 amplitude based on previous-trial conflict. CONCLUSIONS   Lack of electrophysiological conflict adaptation effects in youth with ASD indicates irregular neural processing associated with conflict adaptation. Individuals with ASD show declines in level of conflict evaluation and adaptation. Future research is necessary to accurately characterize and understand the behavioral implications of these cognitive control deficits relative to diagnostic severity, anxiety, and personality.

Cognitive conflict adaptation in generalized anxiety disorder

Individuals with generalized anxiety disorder (GAD) display poor emotional conflict adaptation, a cognitive control process requiring the adjustment of performance based on previous-trial conflict. It is unclear whether GAD-related conflict adaptation difficulties are present during tasks without emotionally-salient stimuli. We examined conflict adaptation using the N2 component of the event-related potential (ERP) and behavioral responses on a Flanker task from 35 individuals with GAD and 35 controls. Groups did not differ on conflict adaptation accuracy; individuals with GAD also displayed intact RT conflict adaptation. In contrast, individuals with GAD showed decreased amplitude N2 principal component for conflict adaptation. Correlations showed increased anxiety and depressive symptoms were associated with longer RT conflict adaptation effects and lower ERP amplitudes, but not when separated by group. We conclude that individuals with GAD show reduced conflict-related component processes that may be influenced by compensatory activity, even in the absence of emotionally-salient stimuli.

Conflict and performance monitoring throughout the lifespan: An event-related potential (ERP) and temporospatial component analysis

Cognitive control includes higher-level cognitive processes used to evaluate environmental conflict. Given the importance of cognitive control in regulating behavior, understanding the developmental course of these processes may contribute to a greater understanding of normal and abnormal development. We examined behavioral (response times [RTs], error rates) and event-related potential data (N2, error-related negativity [ERN], correct-response negativity [CRN], error positivity [Pe]) during a flanker task in cross-sectional groups of 45 youth (ages 8-18), 52 younger adults (ages 20-28), and 58 older adults (ages 56-91). Younger adults displayed the most efficient processing, including significantly reduced CRN and N2 amplitude, increased Pe amplitude, and significantly better task performance than youth or older adults (e.g., faster RTs, fewer errors). Youth displayed larger CRN and N2, attenuated Pe, and significantly worse task performance than younger adults. Older adults fell either between youth and younger adults (e.g., CRN amplitudes, N2 amplitudes) or displayed neural and behavioral performance that was similar to youth (e.g., Pe amplitudes, error rates). These findings point to underdeveloped neural and cognitive processes early in life and reduced efficiency in older adulthood, contributing to poor implementation and modulation of cognitive control in response to conflict. Thus, cognitive control processing appears to reach peak performance and efficiency in younger adulthood, marked by improved task performance with less neural activation.