ERP--correlates of response selection in a response conflict paradigm.

Neuroimaging and electrophysiological studies suggest that the anterior cingulate cortex (ACC) is involved in the cognitive control of response related action. A frontocentral negative ERP-component, the N2, which probably originates from the ACC, is usually enhanced in conflict-trials that demand an unexpected response. We here used stepped adjustment of response expectation in a response-cueing task, and measured how the N2 varied with global and local cue validity. Results showed that, irrespective of the current cue validity, response times, error rates, and the frontocentral components P2, N2 and P3 increased in unexpected trials. Nevertheless, a N2 was also seen in expected trials, and its latency correlated positively with reaction times, indicating that this potential does not express response conflict only. In line with roles suggested for the ACC, we here propose that the N2 is related to the process of response selection which influences subsequent processing stages reflected in the P3. Unexpected revisions of response programs enhance and delay the N2.