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Abstract:
High density ERPs were used to investigate the time course of
the Stroop effect in the human brain. Congruent (the word "BLUE" in
blue ink) and incongruent (the word "RED" in blue ink) Stroop
conditions displayed similar temporal and spatial patterns in both
manual (Exp. 1) and vocal response (Exp. 2). In both experiments,
the congruent and incongruent conditions first diverged from the
neutral condition (a non-color word; e.g., "KNIFE" in blue ink) at
268 msecs over midline and lateral posterior electrode sites, but
did not diverge from each other until response. Dipole modeling of
the congruent and incongruent conditions produced matching neural
solutions consistent with a cingulate gyrus generator, suggesting
activation of an executive attentional system in both conditions.
These results suggest comparable selective attentional processes to
resolve conflict in both the congruent and incongruent Stroop
conditions. This conflict arises in trials in which a word
activates a color name area which, in turn, begins to activate a
color response. Color word trials require selection between
information from the word and the color (independent of the
congruity of the trial type). The current data provide convergent
evidence with recent blood flow studies of the Stroop effect and
help to resolve some of the discrepancies in this
literature.
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