Conflict and the evaluative functions of the anterior cingulate: Converging evidence from event-related fMRI and high density ERP

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6, 2001,

Part 2 of 2

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Conflict and the Evaluative Functions of the Anterior Cingulate: Converging Evidence from Event-related fMR1 and High Density ERP Cameron Carter*, Vincent Van Veen, Matthew Botvinick, Jonathan Cohen?+, V. Andrew Stenger* *University of Pittsburgh t University of Pittsburgh $Princeton University A growing body of data associates the anterior cingulate cortex (ACC) with evaluative functions related to performance monitoring during cognition. However the relationship between error-related activity and conflict related activity in this region, as well a$ the kinds of conflict that activate the ACC, remains controversial. We used event-related fMRI and high density ERP during a version of the Eriksen flanker paradigm that separately manipulated conflict at the response level and at the stimulus level to address these issues. Both forms of conflict produced increased reaction times, however only conflict at the response level activated the AK during tMRI, even when we controlled for differences for the magnitude of the RT effect of stimulus and response conflict. The “conflict theory ” hypothesizes that an evaluative function by the ACC is implemented through the detection of conflict. and that the error related activity which is reliably observed in this region of the brain reflects conflict between the executed, incorrect response and the correct one during ongoing stimulus evaluation after an impulsive error. This theory predicts that ACC activity related to response conflict during correct trials on a task like the Eriksen will occur prior to the response (“pre-response conflict”). while ACC activity associated with errors will be observed in the period immediately following an error (“post-response conflict”). In a second experiment using the same behavioral paradigm during ERP recording we observed, in stimulus aligned data, that a component of the N2 showed the same modulation by response conflict but not stimulus conflict as that observed in the ACC during fMRI. This waveform showed the same fronto-central surface topography as the error-related negativity (ERN, observed in response aligned data), and source localization confirmed that the N2 related signature of response conflict and the ERN both localized tqthe same region of the ACC. These data are consistent with the “conflict theory” of ACC evaluative functions. wherein a region of the ACC contributes to performance monitoring and the modulation of executive control by detecting response conflict. Interesting dissociations along the rostra-caudal extent of the ACC were observed in the ERP study among components of the error related signal. The ERN clearly co-localized with response conflict related activity in caudal ACC. In contrast, a component of the error related positivity, which follows the ERN and may represent an affective response to making an error, showed a rostra1 ACC source. These findings shed light on recent claims, based upon the presence of more rostra1 ACC activity associated with error5 during fMRI, that error detection and conflict monitoring might be localized to different subregions of the ACC.

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