Impulsivity and conflict in the stroop task: an ERP study
It has been suggested that impulsive behavior can be attributed to weaker interference control. The present research used a Stroop task to test whether impulsivity within the normal population is associated with weaker interference control. Sixteen high- and 16 low-impulsive healthy volunteers performed a Stroop task, which varied in the proportion of incongruent trials to induce high conflict and provoke more impulsive behavior. Event-related brain potentials (ERP) were recorded to assess the brain correlates of Stroop interference (N/P450 and SP [sustained potential]), which have been suggested to reflect conflict processing and attentional control, respectively. Higher conflict resulted in more Stroop interference and enhanced N/P450 and SP. Source analyses indicated that the neural generators of the N/P450 and the SP may both be located near the anterior cingulate cortex (ACC), suggesting that both may reflect aspects of conflict processing. Differences in Stroop interference in terms of error rates, but not in terms of reaction time were found between high and low impulsives. This result may reflect enhanced sensitivity to the surprise value of unexpected stimulus categories, rather than enhanced interference. High impulsive participants did not differ from low impulsive participants with respect to the N/P450, but the SP seemed to originate from a more posterior and right-sided cortical network in high impulsive relative to low impulsive participants. In conclusion, high impulsiveness within the normal population as assessed by an impulsivity questionnaire is not associated with relatively early processes during response inhibition, but the present results may suggest an association between impulsiveness and further, more complex conflict processing.