Patterns of brain activation associated with covert
performance of the Stroop Color–Word task were studied
in young, healthy, adult volunteers using blood oxygen
level dependent (BOLD) functional magnetic resonance imaging
(fMRI). Comparisons of the incongruous Stroop condition
were made with both color naming and word reading baselines.
Areas of the left and right anterior cingulate, the right
precuneus, and the left pars opercularis displayed larger
BOLD signal responses during the incongruous Stroop condition
than during baseline conditions. Activation of BOLD signals
in these areas was highly repeatable. In a second experiment,
pupil diameter was used to assess cognitive load in 7 individuals
studied during overt and covert performance of both Stroop
and color naming conditions. Cognitive load was similar
in overt and covert response conditions. Results from the
BOLD study indicate that brain regions participating in
selective visual attention and in the selection of motor
programs involved in speech were activated more by the
Stroop task than by the baseline tasks. The neural substrate
involved in the resolution 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 of brain regions is implicated, with separate regions
within this system supporting distinct functions. (JINS,
1999, 5, 308–319.)