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Abstract:
GOALS To analyse the neuronal network of executive control
functions, we must identify not only the participating brain
regions but also the time course of neuronal activation. This study
investigated the neuronal organization of the Stroop color-word
interference effect in event-related potentials (ERPs). The Stroop
test requires executive control functions and particularly
inhibition of a learned routine (in this case word reading).
METHODS Eight healthy subjects were tested using high-density
(64 channels) ERPs. Subjects were instructed to respond to the
display color of the word. Display color was neutral, congruent or
incongruent with word meaning.
RESULTS AND CONCLUSIONS Behavioral data yielded a robust Stroop
effect as indicated by longer reaction times for incongruent than
congruent words. ERP revealed the neurophysiological substrate of
this interference effect: A first effect consisted of a greater
negativity to incongruent than to congruent and neutral words
between 350-500 post-stimulus time over left fronto-central and
tempo-parietal scalp regions. Later on in time, a prolonged
positivity greater to incongruent than to congruent and neutral
words developed between 600-1000 ms post-stimulus over
centro-parietal scalp regions. The early effect may reflect the
inhibition processes themselves and the later effect the
postevaluation of the performance after the response has been
delivered.
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