Brain activation and pupil response during covert performance of the Stroop Color Word task

Patterns of brain activation associated with covert performance of the Stro op Color-Word task were studied in young, healthy, adult volunteers using b lood oxygen level dependent (BOLD) functional magnetic resonance imaging (f MRI). Comparisons of the incongruous Stroop condition were made with both c olor naming and word reading baselines. Areas of the left and right anterio r cingulate, the right precuneus, and the left pars opercularis displayed l arger BOLD signal responses during the incongruous Stroop condition than du ring baseline conditions. Activation of BOLD signals in these areas was hig hly repeatable. In a second experiment,pupil diameter was used to assess co gnitive load in 7 individuals studied during overt and covert performance o f both Stroop and color naming conditions. Cognitive load was similar in ov ert and covert response conditions. Results from the BOLD study indicate th at brain regions participating in selective visual attention and in the sel ection of motor programs involved in speech were activated more by the Stro op task than by the baseline tasks. The neural substrate involved in the re solution of the perceptual and motor conflicts elicited by the Stroop Color -Word task does not appear to be a single brain region. Rather, a network o f brain regions is implicated, with separate regions within this system sup porting distinct functions.