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Parametric Manipulation of the Conflict Signal and Control-stateAdaptationSarah E. Forster 1 , Cameron S. Carter 2 , Jonathan D. Cohen 3 , and Raymond Y. Cho 11 University of Pittsburgh2 University of California, Davis3 Princeton UniversityAbstractMechanisms by which the brain monitors and modulates performance are an important focus ofrecent research. The conflict-monitoring hypothesis posits that the ACC detects conflict betweencompeting response pathways which, in turn, signals for enhanced control. The N2, an ERPcomponent that has been localized to ACC, has been observed after high conflict stimuli. As acandidate index of the conflict signal, the N2 would be expected to be sensitive to the degree ofresponse conflict present, a factor that depends on both the features of external stimuli and theinternal control state. In the present study, we sought to explore the relationship between N2amplitude and these variables through use of a modified Eriksen flankers task in which target–distracter compatibility was parametrically varied. We hypothesized that greater target–distracterincompatibility would result in higher levels of response conflict, as indexed by both behavior andthe N2 component. Consistent with this prediction, there were parametric degradations inbehavioral performance and increases in N2 amplitudes with increasing incompatibility. Further,increasingly incompatible stimuli led to the predicted parametric increases in control onsubsequent incompatible trials as evidenced by enhanced performance and reduced N2 amplitudes.These findings suggest that the N2 component and associated behavioral performance are finelysensitive to the degree of response conflict present and to the control adjustments that result frommodulations in conflict.INTRODUCTIONCognitive control describes the set of processes responsible for task-appropriate perceptualselection and response biasing, especially in face of distracting stimulus information or task-inappropriate responses tendencies (Botvinick, Braver, Barch, Carter, & Cohen, 2001;Miller & Cohen, 2001). Evaluative mechanisms that monitor performance are thought toprovide critical feedback in the modulation of control and have become a focus of greatinterest in recent years. The conflict hypothesis posits one such mechanism, by which thereis monitoring for conflict between competing response pathways, signaling a need foradditional control resources when high levels of conflict are detected (Botvinick et al., 2001,2004). Numerous studies have provided empirical evidence consistent with such conflict-mediated control adjustments (Cho, Orr, Cohen, & Carter, 2009; Kunde & Wühr, 2006;Egner & Hirsch, 2005b; Ullsperger, Bylsma, & Botvinick, 2005; Kerns et al., 2004;Stürmer, Leuthold, Soetens, Schroter, & Sommer, 2002; Gratton, Coles, & Donchin, 1992),Reprint requests should be sent to Raymond Y. Cho, Western Psychiatric Institute and Clinic, University of Pittsburgh, 3811 O’HaraSt., Oxford 454, Pittsburgh, PA 15213, or via chory@upmc.edu.NIH Public AccessAuthor ManuscriptJ Cogn Neurosci. Author manuscript; available in PMC 2011 April 1.Published in final edited form as:J Cogn Neurosci . 2011 April ; 23(4): 923–935. doi:10.1162/jocn.2010.21458.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript