An illustration of the (A) Stroop task and (B) multi-source interference task (MSIT) paradigms. Shown for both tasks are sample trials from the incongruent (top) and congruent (bottom) task conditions, as administered in a blocked fMRI paradigm. Participants completed four blocks of the two conditions in each task, with each block lasting 54–58 sec and beginning with a 12–16 sec fixation cue. For the incongruent condition of each task, trials were presented with a variable stimulus onset asynchrony (SOA) to maintain task accuracy across participants to control for individual differences in task performance. For the congruent condition of both tasks, trials were presented at a fixed SOA, defined by the mean SOA of the preceding incongruent condition. A brachial blood pressure cuff was inflated during each fixation period, and readings of oscillometric blood pressure and heart rate were obtained by the end of each congruent and incongruent condition in both tasks.