Processing conflicting information: facilitation, interference, and functional connectivity.

When a conflict task involves congruent, neutral, and incongruent conditions, it is possible to examine facilitation (neutral vs. congruent) and interference (incongruent vs. neutral) components. Very few studies investigated the brain areas that are specifically involved in facilitation or interference. We used functional magnetic resonance imaging while participants performed a magnitude conflict task (the size congruity paradigm). We observed four findings: (1) while most of the brain areas that were activated by conflict tasks showed interference effects, the intraparietal sulcus was the only region activated for both interference and facilitation components. (2) Two groups of participants could be distinguished based on the pattern of anterior cingulate cortex (ACC) activity, one with classical facilitation (congruent<neutral), one with reverse facilitation. (3) Functional connectivity analysis of the areas that were modulated by the conflict task revealed an anterior cingulate - lateral prefrontal cortex network and a dorsal parietal - premotor cortex network. We suggest that the former plays a role in cognitive control and conflict detection, whereas the latter participates in top-down selection of task-relevant stimuli and response mapping. (4) These networks were modulated by the two groups that we distinguished based on the ACC activation.