PerspectiveNeuroscience

Conflict and Cognitive Control

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Science  13 Feb 2004:
Vol. 303, Issue 5660, pp. 969-970
DOI: 10.1126/science.1094733

Cognitive control [HN1] is necessary when we block a habitual behavior and instead execute a less-familiar behavior. Because cognitive control requires an effort, it is not efficient to maintain a high level of control all the time—the nervous system needs to know when cognitive control is necessary. On page 1023 of this issue, Kerns et al. (1) [HN2] investigate the brain mechanisms that underlie the recruitment of cognitive control.

Two cortical areas in the frontal part of the brain, the anterior cingulate cortex [HN3] (ACC) and the lateral prefrontal cortex [HN4] (LPFC), are considered essential for recruiting cognitive control. This conclusion is based both on the psychological examination of brain-damaged patients and on the imaging of normal human subjects (2). Botvinick and colleagues have proposed that the ACC detects conflicts between plans of action, and in response to these conflicts recruits greater cognitive control in the LPFC (3) [HN5]. This hypothesis is consistent with evidence showing the involvement of the LPFC in the execution of cognitive control, such as selective attention and response inhibition (4). Activation of the ACC by action-plan conflicts has also been reported (57) [HN6]. However, as yet there is no direct evidence of a connection between the detection of conflicts in the ACC and the subsequent greater control recruited in the LPFC.

The Stroop test [HN7] is a useful tool for examining this connection. In this test, words denoting colors (such as red or green) are presented to human subjects in a variety of different colors, one at a time. The subject is instructed to report the physical color in which the word is presented (the color-naming condition) or the color that the word denotes (the word-reading condition). Subjects find it difficult to respond correctly in the color-naming condition when the physical color of the presented word is different from its meaning (incongruent). This difficulty is apparent not only in the subject's frequency of erroneous responses but also in the subject's reaction time for correct responses. The reaction time tends to be longer in incongruent trials than in congruent trials (where the physical color matches the meaning). Because human subjects are well trained to read words, a motor plan for reading the presented word is spontaneously initiated, contrary to the instruction to report the color in which the word is presented. This results in a conflict between two plans of response actions, which in turn increases the reaction time (see the figure, left). Functional magnetic resonance imaging (fMRI) [HN8] has revealed greater activation in the ACC during incongruent versus congruent trials (6).

Recruiting cognitive control.

Using fMRI, Kerns et al. (1) examined activation of the ACC and LPFC in consecutive trials of the Stroop test in human subjects. (Left) When the word presented to subjects is in a different color from the color the word denotes—an incongruent trial (i)—the resulting conflict regarding which action plan to execute induces an increase in ACC activity. (Right) When the first incongruent trial is followed by a second incongruent trial (i + 1), there is increased activity in the LPFC due to recruitment of cognitive control during the first trial, resulting in a shorter reaction time for the test response. The authors propose that detection of conflicts between plans of action by the ACC leads to recruitment of cognitive control in the LPFC.

CREDIT: TAINA LITWAK

When an incongruent trial is followed by another incongruent trial, it is expected that a conflict detected in the first trial recruits greater cognitive control in the second trial. Thus, there should be stronger control in incongruent trials that follow an incongruent trial compared with incongruent trials that follow a congruent trial (see the figure, right). This expectation has been confirmed by comparing the reaction times in the two types of incongruent trials. However, neural correlates of this sequence, that is, detecting conflicts in one trial and greater cognitive control in the next trial, have not been shown. By using event-related fMRI [HN9], Kerns et al. now report correlations between ACC activity, LPFC activity, and reaction time in subjects performing the Stroop color-naming task. Specifically, these authors found that ACC activity in an incongruent trial had a positive correlation with LPFC activity in the next trial. They also found that ACC activity in an incongruent trial had a negative correlation with the reaction time of the subject in the following incongruent trial. These findings should garner more support for the proposal that the ACC recruits control in the LPFC based on conflict monitoring.

Kerns et al. (1) propose that the ACC strengthens the cognitive control recruited by the LPFC, and that the ACC does not specify the manner or direction of control. Their previous studies showed that the ACC was not activated when the subject strengthened attention to the relevant sensory dimension (physical color in the color-naming condition) before a sample word was presented in the trial (6). However, subjects succeeded in responding correctly in most incongruent trials, although the reaction times were longer, indicating that the conflicts were somehow resolved within the trial. The ACC may contribute to this “consequential” control enabling selection of one of the two action plans evoked by the word presentation.

The cingulate motor area of the ACC has direct projections to the primary motor cortex [HN10]. The remaining parts of the ACC have indirect projections to the primary motor cortex via the cingulate motor area and other medial higher motor areas (8). Moreover, recent single-cell recording studies in monkeys suggest mechanisms by which the ACC resolves conflicts between action plans. When monkeys select one of two actions based on anticipation of the goal (reward type) and recent experience of the contingency between action and goal, the neuronal activity representing the anticipated goal occurs first. Then neuronal activity representing a combination of the anticipated goal and intended action occurs after a short delay in the ACC (9) [HN11]. The former neuronal activity might trigger the latter, and this sequence of activities might underlie goal-based action selection. Neuronal activities in the ACC that are specific for the selection of particular actions have also been found in other studies (10, 11). Sensory cues may evoke multiple action plans, one of which is selected by the ACC according to such values as the anticipated goal and whether the action is justified.

Cognitive control recruited by the ACC may be “consequential,” that is, based on conflicts between evoked plans of concrete actions. In contrast, in the LPFC, control may be “preemptive,” that is, capable of preventing future conflicts, and may occur at a more strategic level, for example, by increasing attention to the task-related aspects of sensory stimuli. Because neurons selective for different actions are interspersed in local regions, the limited spatial resolution of fMRI might have obscured these action-specific activities in the ACC in previous fMRI studies. Future studies in monkeys and humans should elucidate further the mechanisms defining consequential and preemptive cognitive control and the parts played by the ACC and LPFC.

HyperNotes Related Resources on the World Wide Web

General Hypernotes

Dictionaries and Glossaries

A neuroscience glossary is provided by the Neuroscience at a Glance Companion Web site.

An illustrated glossary of neuroanatomy is provided by the HyperBrain Web site.

A glossary is provided by the Brain Connection Web site.

Web Collections, References, and Resource Lists

The Google Directory provides a collection of links to Internet neurobiology resources.

The Yahoo Directory provides links to Internet resources on cognitive science.

Neurosciences on the Internet (Neuroguide.com) is a searchable and browsable index of Internet neuroscience resources maintained by N. Busis, Division of Neurology, UPMC Shadyside Hospital, Pittsburgh.

Neuroanatomy & Neuropathology on the Internet is an extensive collection of resources and Internet links maintained by K. Hegedüs, Department of Neurology, University of Debrecen, Hungary. A reference on neuroanatomy structures is included.

NeuralLinksPlus is provided by M. Dubin, Department of Molecular, Cellular, and Developmental Biology, University of Colorado.

FunctionalMRI.org provides links to Internet resources related to functional magnetic resonance imaging (fMRI).

Online Texts and Lecture Notes

An introduction to the human brain and nervous system is provided by Kimball's Biology Pages, an online biology textbook and glossary.

An exploration of the nervous system is provided by E. Chudler's Neuroscience for Kids Web site. A glossary of neuroscience words is included. A collection of links to Internet neuroscience education resources is available on E. Chudler's home page at the Department of Anesthesiology, University of Washington.

The University of Washington's BrainInfo is a resource on structures in the brain.

The Centre for Psychology, Athabasca University, Canada, provides biological psychology tutorials.

S. Kornguth, Department of Neurobiology and Institute for Advanced Technology, University of Texas, provides lecture notes for a neuroscience course on the brain.

J. Rueckl, Department of Psychology, University of Connecticut, provides lecture notes for a course on cognitive psychology. A presentation on the neural basis of cognition is included.

D. Lee, Department of Brain and Cognitive Sciences, University of Rochester, offers lecture notes for a course on sensory and motor neuroscience.

J. Culham, Department of Psychology, University of Western Ontario, makes available a Web course on fMRI.

The UCLA Brain Mapping Center makes available readings and other resources for a course on functional neuroimaging.

General Reports and Articles

Papers from a NAS Colloquium on Neuroimaging of Human Brain Function were published in the 3 February 1998 issue of the Proceedings of the National Academy of Sciences.

J. Allman, Division of Biology, California Institute of Technology, makes available a review by J. Allman et al. titled “The anterior cingulate cortex: The evolution of an interface between emotion and cognition” (published in volume 935 of the Annals of the New York Academy of Science).

G. Bush, Cingulate Cortex Research Laboratory, Massachusetts General Hospital-East, makes available in PDF format a review article (published in the June 2000 issue of Trends in Cognitive Sciences) by G. Bush, P. Luu, and M. I. Posner titled “Cognitive and emotional influences in anterior cingulate cortex.”

E. K. Miller, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, makes available in PDF format a review article (from the 2001 Annual Review of Neuroscience) by E. K. Miller and J. D. Cohen titled “An integrative theory of prefrontal cortex function,” as well as a October 2000 review article (from Nature Reviews Neuroscience) titled “The prefrontal cortex and cognitive control.”

The 12 March 1999 issue of Science had a review by E. E. Smith and J. Jonides titled “Storage and executive processes in the frontal lobes.”

Numbered Hypernotes

1. Cognitive control. “Neural mechanisms of cognitive control” by J. D. Cohen is a slide presentation from a 2000 conference, made available by the Center for Health and Wellbeing, Princeton University. N. Rougier, the Cortex Group, Loria Laboratory, Nancy University, France, makes available in PDF format a slide presentation by T. Braver titled “Prefrontal mechanisms of cognitive control” (from a 20 October 2003 workshop). The 14 November 2003 issue of Science had a Research Article by E. Koechlin, C. Ody, and F. Kouneiher titled “The architecture of cognitive control in the human prefrontal cortex” and a related News of the Week article by L. Helmuth titled “Brain model puts most sophisticated regions front and center.”

2. John G. Kerns is in the Department of Psychological Sciences, University of Missouri, Columbia, and in the Department of Psychiatry, University of Pittsburgh. Jonathan D. Cohen is in the Department of Psychology, Princeton University, and in the Department of Psychiatry, University of Pittsburgh. Angus MacDonald III is in the Department of Psychology, University of Minnesota, Minneapolis. Raymond Y. Cho is at the Laboratory for Clinical Cognitive Neuroscience, Department of Psychiatry, University of Pittsburgh. V. Andrew Stenger is at the Magnetic Resonance Research Center and in the Department of Radiology, University of Pittsburgh Medical Center. Cameron S. Carter is at the Laboratory for Clinical Cognitive Neuroscience, Department of Psychiatry, University of Pittsburgh, and at the Imaging Research Center, University of California, Davis.

3. Anterior cingulate cortex (ACC). Anterior cingulate gyrus is defined in the Brain Connection glossary. BrainInfo has an entry for anterior cingulate gyrus. The Department of Physiology, University of Oklahoma Health Sciences Center, provides a study aid diagram of the location of the cingulate cortex. Athabasca University's Centre for Psychology provides an introduction to the cingulate gyrus in a tutorial on the limbic system. A slide show of captioned images related to the ACC is made available by Nature Reviews Neuroscience; these figures accompanied a 9 June 2001 review article by T. Paus titled “Primate anterior cingulate cortex: Where motor control, drive and cognition interface.” The 1 May 1998 issue of Science had a report by C. S. Carter et al. titled “Anterior cingulate cortex, error detection, and the online monitoring of performance.” The 13 May 2002 issue of Science had a report by M. Shidara and B. J. Richmond titled “The anterior cingulate: Single neuronal signals related to degree of reward expectancy” and a related Perspective by L. L. Peoples titled “Will, anterior cingulate cortex, and addiction.”

4. Prefrontal cortex. BrainPlace.com offers a diagram showing the location of the lateral prefrontal cortex. A. Anderson, Department of Psychology, University of Toronto, provides lecture slides (in PDF format) on the prefrontal cortex for a course on cognitive neuroscience. A course on brain and behavior, offered by the Department of Psychiatry, University of Illinois, Chicago, makes available (in PDF format) a lecture slide presentation by M. Gaviria titled “Prefrontal cortex systems and behavior.” A slide show on the human prefrontal cortex is made available by Nature Reviews Neuroscience; these figures accompanied a February 2003 review article by J. N. Wood and J. Grafman titled “Human prefrontal cortex: Processing and representational perspectives.” The Companion Web site for Gazzaniga and Heatherton's Psychological Science offers an interview with M. D'Esposito about his research on the lateral prefrontal cortex. The 19 March 2002 issue of the Proceedings of the National Academy of Sciences had an article by J. R. Gray, T. S. Braver, and M. E. Raichle titled “Integration of emotion and cognition in the lateral prefrontal cortex.”

5. The Neuroscience of Cognitive Control Laboratory at Princeton University makes available in PDF format the July 2001 article (published in Psychological Review) by M. M. Botvinick, T. S. Braver, D. M. Barch, C. S. Carter, and J. D. Cohen titled “Conflict monitoring and cognitive control” (3).

6. Activation of the ACC by action-plan conflicts. The 9 June 2000 issue of Science had a report by A. W. MacDonald, J. D. Cohen, V. A. Stenger, and C. S. Carter titled “Dissociating the role of dorsolateral prefrontal cortex and anterior cingulate cortex in cognitive control” (6). J. D. Cohen makes available in PDF format the 11 November 1999 Nature article by M. M. Botvinick et al. titled “Conflict monitoring versus selection-for-action in anterior cingulate cortex” (5) and the December 2001 NeuroImage article by V. van Veen et al. titled “Anterior cingulate cortex, conflict monitoring, and levels of processing” (7).

7. Stroop test. The American Psychological Association provides an introduction to the Stroop effect. A presentation on the Stroop effect (with demonstrations of the Stroop test) is provided by E. Chudler's Exploring the Nervous System. A presentation on the Stroop task is provided by the Environmental Psychology Lab, University of Michigan; a demo in Shockwave format is included. J. Ridley Stroop's 1935 article titled “Studies of interference in serial verbal reactions” is made available by C. Green's Classics in the History of Psychology Web site. Vanderbilt University's Daily Register makes available an October 2002 article about J. Ridley Stroop titled “Stroop effect helps put Vanderbilt on psychology map.”

8. Functional magnetic resonance imaging (fMRI).How MRI works by T. Gould is an introduction provided by Marshall Brain's How Stuff Works Web site. The Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, Department of Clinical Neurology, University of Oxford, offers an introduction to fMRI. A presentation on fMRI is provided by the Functional MRI Research Center, Columbia University. D. C. Noll, Functional MRI Laboratory, University of Michigan, makes available (in PDF format) a primer on MRI and fMRI. S.-G. Kim, Brain Imaging Research Center, University of Pittsburgh, makes available in PDF format a presentation titled “Principles of functional MRI.” Neuroguide.com offers an article by T. Gregg titled “Use of functional magnetic resonance imaging to investigate brain function.”

9. Event-related fMRI.R. Henson, Wellcome Department of Imaging Neuroscience, University College London, makes available in PDF format a paper titled “Event-related fMRI: Introduction, statistical modelling, design optimisation and examples.” The 3 February 1998 issue of the Proceedings of the National Academy of Sciences had an article by B. R. Rosen, R. L. Buckner, and A. M. Dale titled “Event-related functional MRI: Past, present, and future.”

10. A section on the primary motor cortex is included in Athabasca University's Biological Psychology Tutorials. The Washington University School of Medicine's Neuroscience Tutorial includes a presentation on the basic motor pathway. T. Vilis, Department of Physiology and Pharmacology, University of Western Ontario, offers an animated tutorial on the motor cortex for a Web course on neurophysiology.

11. Goal-based action selection in monkey study. The 11 July 2003 issue of Science had a report by K. Matsumoto, W. Suzuki, and K. Tanaka titled “Neuronal correlates of goal-based motor selection in the prefrontal cortex” (9) and a related Perspective by B. J. Richmond, Z. Liu, and M. Shidara titled “Predicting future rewards.”

12. Kenji Matsumoto and Keiji Tanaka are at the Laboratory for Cognitive Brain Mapping, RIKEN Brain Science Institute, Wako, Saitamo, Japan.

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