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Abstract:
Background. ERP studies of error-related negativity (ERN)
have been localized to ACC. PET, fMRI and ERP studies have also
identified Stroop interference effects in ACC. Aim. To use
high-density ERPs to study localization and time course of Stroop
interference and ERN effects in ACC within the same subjects and
tasks. Methods. Eight healthy volunteers performed a 4-key manual
version of the Stroop task and a 4-key non-color control task. ERPs
were averaged separately to stimulus onset and response onset.
Results. RT and error analyses produced significant interference
effects (mean RT effect: 110 ms). Stroop Interference effect. A
significant interference effect (Incongruent word more negative)
was present over frontocentral medial scalp (peak=400 ms,
p<.001). ERN effect. A significant ERN effect was also present
over frontocentral medial scalp, in both the Stroop and control
tasks (peak=80 ms, for both, p<.01). Colocalization. Scalp
topographies of the Stroop and ERN effects appeared highly similar.
Dipole source analyses (BESA) for both effects, seeded with
identical coordinates (from PET activations or individual BESA
solutions), yielded residual variances of about 10% (one ACC
dipole) or 3% (second dipole in frontal cortex). Conclusion. The
same region of ACC may be specialized for both conflict monitoring
in the Stroop task and in error detection. Dichotomous theories of
conflict monitoring and error detection may require
reconciliation.
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