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Abstract:
The electrophysiological correlates of the Stroop color-word
interference effect were studied in 8 healthy subjects using
high-density Event-Related Potentials (ERPs). Three response
modalities were compared: Overt Verbal, Covert Verbal, and Manual.
Both Overt Verbal and Manual versions of the Stroop yielded robust
Stroop color-word interference as indexed by longer RTs for
incongruent than congruent color words. The Incongruent vs.
Congruent ERP difference wave presented two effects. There was
first a focal negativity centered around the anterior medial
frontal region between 350-500 ms post-stimulus (peak at 410 msec).
This effect was present for Overt and Covert Verbal conditions but
for the Manual version it to was smaller (non-significant) and had
a broader scalp distribution. Later on in time a posterior,
prolonged positivity developed between 500-800 ms post-stimulus
over left superior temporo-parietal scalp. This effect was present
for all the three response modalities. A possible interpretation of
these results is that Stroop color-word interference first involves
anterior cingulate cortex or other medial frontal regions (350-500
ms post-stimulus), followed by activation of the left
temporo-parietal cortex, possibly related to the need for
additional processing of incongruent color-word meaning.
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