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A dissociable set of regions was active for the executive processing associated with overcoming a prepotent response tendency and task switching. Regions associated with overcoming prepotency were primarily frontal and may be part of a system involved in top-down biasing for conflict reduction. Posterior regions were recruited for switching between tasks and likely play a role in reconfiguring stimulus-response mappings. Precuneus activity was common to both manipulations and may reflect increased visual attention due to more difficult task demands.

Cognitive control forms a foundation for higher cognitive functions such as attention, memory retrieval, and language production and comprehension. Cognitive control allows us to coordinate or direct lower level or more automatic processes to ensure that our resulting actions will be in line with our goals and to successfully perform difficult tasks, even in the face of distraction. While the behavioral and neural mechanisms of cognitive control are well characterized, a growing body of literature regarding the influence of emotional states and emotional stimuli on performance of goal-related behaviors and neural activity has yielded discrepant results. Conflict and Control in Nonemotional TasksOne particular function of cognitive control is the selection of a correct response from competing responses. In the color-word Stroop task, subjects are required to name the color in which a color word is displayed (Stroop, 1935). On congruent trials, the color and meaning of the word are the same (e.g., the word blue written in blue). Responses on these trials are generally quick and accurate. On incongruent trials, the color and the meaning of the word are not the same (e.g., the word blue written in red). Performance is slower and less accurate on incongruent trials because of the presence of conflict. During these types of trials, cognitive control is needed for the subject to respond with the correct color-naming response ("red") as opposed to the incorrect and conflicting automatic word-reading response ("blue").Behavioral studies have shown that responses to incongruent trials preceded by another incongruent trial (iI trials) are considerably faster and more accurate than responses to incongruent trials preceded by a congruent trial (cI trials; Gratton, Coles, & Donchin, 1992). Performance on iI trials is improved because of a strengthening of selection for action or control. On cI trials, performance is poor, because control is not yet implemented and levels of conflict are high.In an event-related fMRI study of the color-word Stroop task, Kerns et al. (2004) found that a fast iI trial was associated with high dorsolateral prefrontal cortex (DLPFC) activity and high dorsol anterior cingulate cortex (dACC) activity on the preceding incongruent (cI) trial. This study helped establish the role of the dACC as the conflict monitor and the role of a separate and distinct area, the DLPFC, in subsequent cognitive control. These results have since been replicated in several neuroimaging studies (Egner, Etkin, Gale, & Hirsch, 2008;Egner & Hirsch, 2005;Kerns, 2006), and Egner and Hirsch (2005) later showed that DLPFC improves task performance by enhancing processing of the task-relevant stimulus dimension. Conflict and Control in Emotional TasksThe results described above account for the cognitive and neural underpinnings of conflict detection and subsequent control-related adjustments during cognitive tasks. However, in real-world situations, we must con- 357© 2010 The Psychonomic Society, Inc.Adding fear to conflict: A ge...

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