Original Research ARTICLE

Front. Hum. Neurosci., 24 December 2010 | doi: 10.3389/fnhum.2010.00231

Conditional differences in mean reaction time explain effects of response congruency, but not accuracy, on posterior medial frontal cortex activity

Joshua Carp1*, Kamin Kim1, Stephan F. Taylor2, Kate Dimond Fitzgerald2 and Daniel H. Weissman1
  • 1 Department of Psychology, University of Michigan, Ann Arbor, MI, USA
  • 2 Department of Psychiatry, University of Michigan, Ann Arbor, MI, USA

According to the conflict-monitoring model of cognitive control, the posterior medial frontal cortex (pMFC) plays an important role in detecting conflict between competing motor responses. Consistent with this view, pMFC activity is greater in high-conflict trials (e.g., incongruent trials and errors) than in low-conflict trials (e.g., congruent trials and correct responses) of distractor interference tasks. However, in both low- and high-conflict trials, pMFC activity increases linearly with reaction time (RT). Thus, heightened pMFC activity in high-conflict trials may simply reflect the fact that mean RT is longer in high-conflict than in low-conflict trials. To investigate this hypothesis, we reanalyzed data from a previously published fMRI study in which participants performed an event-related version of the multi-source interference task. Critically, after controlling for conditional differences in mean RT, effects of response congruency on pMFC activity were eliminated; in contrast, effects of response accuracy on pMFC activity remained robust. These findings indicate that effects of response congruency on pMFC activity may index any of several processes whose recruitment increases with time on task (e.g., sustained attention). However, effects of response accuracy reflect processes unique to error trials. We conclude that effects of response accuracy on pMFC activity provide stronger support for the conflict-monitoring model than effects of response congruency.

Keywords: conflict monitoring, error monitoring, reaction time, brain–behavior correlation, fMRI

Citation: Carp J, Kim K, Taylor SF, Fitzgerald KD and Weissman DH (2010) Conditional differences in mean reaction time explain effects of response congruency, but not accuracy, on posterior medial frontal cortex activity. Front. Hum. Neurosci. 4:231. doi: 10.3389/fnhum.2010.00231

Received: 29 September 2010; Accepted: 09 December 2010;
Published online: 24 December 2010.

Edited by:

Srikantan S. Nagarajan, University of California, San Francisco, USA

Reviewed by:

Tracy L. Luks, University of California, San Francisco, USA
Karuna Subramaniam, University of California, San Francisco, USA

Copyright: © 2010 Carp, Kim, Taylor, Fitzgerald and Weissman. This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.

*Correspondence: Joshua Carp, Department of Psychology, 530 Church Street, Ann Arbor, MI 48109, USA. e-mail: jmcarp@umich.edu

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