Anterior cingulate cortex, medial frontal negativity and preceding context: Assessing an EEG-based neural correlate of performance monitoring during a Stroop task

Flexible goal-directed behavior requires a system that is to adapt to changing task demands and contexts. Current models suggest that anterior cingulate cortex (ACC) activity may serve a performance monitoring function that tracks when behavior may deviate from desired goals. Frontal-midline EEG activity, particularly in the form of negative deflections in event-related brain potentials (ERPs), has been considered to reflect aspects of ACC functioning and performance monitoring. In the current study, a medial frontal negativity observed shortly after correct responses, termed the correct-related negativity (CRN), is assessed during performance of a uniquely modified Stroop color-identification task. In a Stroop task, the two dimensions of a stimulus can he either compatible (C) or incompatible (I) (C: the word "RED" in red hue; I: the word "RED" in blue hue). The reaction time difference between I and C trials (the interference effect) has been shown to depend upon the context in which the trial is delivered (e.g., the compatibility-level of the preceding trial). In the present task, context was manipulated not only by the compatibility-level of the preceding trial but also by the number of preceding-trials before an ending-trial of interest. EEG data were collected during task performance and processed with a blind source separation (BSS) algorithm to extract frontal-midline activity from other neural processes and artifactual signals. The CRN observed in the response-locked ERPs computed from frontal-midline component activations was found to be affected by the task contextual manipulations. The modulation of the CRN amplitude appeared to be inconsistent with expectations formulated from the conflict-monitoring hypothesis.