ORIGINAL PAPER High and Low Stimulus-Driven Conflict Engage Segregated Brain Networks, Not Quantitatively Different Resources

Abstract Task-irrelevant information is constantly pres-ent in our environment and may interfere with the pro-cessing of the information necessary to achieve goal-directed behavior. While task goals determine which information must be suppressed, the demand for inhibitory control depends on the strength of the interference induced by incoming, task-irrelevant information. Whether the same or distinct inhibitory processes are engaged to sup-press various degrees of interference from task-irrelevant information remains largely unresolved. We investigated this question by manipulating the strength of the conflict induced by automatic word reading in a classical color Stroop task. High conflict was induced by presenting words in participant’s native language and low conflict by pre-senting words in a less familiar language. Behavioral per-formance and electrical neuroimaging analyses of event-related potentials to the words were analyzed following a two-by-two within-subject design with factors conflict strength (high; low) and color word/word ink congruency (congruent; incongruent). Behaviorally, we observed a significant conflict strength 9 congruency driven by a smaller Stroop effect in the low- than high conflict condi-tion. Electrophysiologically, we observed a significant conflict strength 9 congruency interaction at the topo-graphic level during the period of the N450 components, indicative of the engagement of distinct configurations of brain networks. No such interaction was found at the level of response strength. Electrical sources analyses localized the topographic effect within the anterior cingulate cortex and basal ganglia, left middle frontal and occipital areas. We interpret our results in terms of qualitatively distinct executive mechanisms for reactive inhibitory control in conditions of high versus low stimulus-driven conflict