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Abstract:
We have previously demonstrated that a number of right
hemisphere regions appear to underlie response inhibition (Garavan
et al., 1999, Proc Natl Acad Sci USA 96). We now report greater
functional specificity through a comparison of successful and
unsuccessful inhibitions using event-related fMRI. Subjects (n=14)
completed a Go/No Go task in which stimulus presentation times were
individually tailored to ensure approximately equal numbers of
successful and unsuccessful inhibitions. Stimuli were a serial
stream of letters (1180 Go, 80 No Go) and active brain areas were
identified using deconvolution and hemodynamic modelling
techniques. Successful inhibition activation largely confirmed our
previous results (right dorsolateral prefrontal, insula and
parietal regions plus midline pre-SMA activation). Critically, all
areas were also activated during unsuccessful inhibitions
(commission errors) with the exception of the right dorsolateral
prefrontal region. Furthermore, commission errors were associated
with a distinct anterior cingulate region that may underlie error
detection (MacDonald et al., 2000, Science 288). Thus, there is
evidence of a double dissociation between specific executive
functions and distinct brain regions (right prefrontal cortex may
be critical for inhibitory control and the anterior cingulate for
error detection) suggesting a neuroanatomical separation of these
higher-order cognitive processes. Funding- GCRC M01-RR00058, NIDA
DA09465.
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