Academic journal article Cognitive, Affective and Behavioral Neuroscience

Stimulus and Response Conflict Processing during Perceptual Decision Making

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Stimulus and Response Conflict Processing during Perceptual Decision Making

Article excerpt

Encoding and dealing with conflicting information is essential for successful decision making in a complex environment. In the present fMRI study, stimulus conflict and response conflict are contrasted in the context of a perceptual decision-making dot-motion discrimination task. Stimulus conflict was manipulated by varying dot-motion coherence along task-relevant and task-irrelevant dimensions. Response conflict was manipulated by varying whether or not competing stimulus dimensions provided evidence for the same or different responses. The right inferior frontal gyrus was involved specifically in the resolution of stimulus conflict, whereas the dorsal anterior cingulate cortex was shown to be sensitive to response conflict. Additionally, two regions that have been linked to perceptual decision making with dot-motion stimuli in monkey physiology studies were differentially engaged by stimulus conflict and response conflict. The middle temporal area, previously linked to processing of motion, was strongly affected by the presence of stimulus conflict. On the other hand, the superior parietal lobe, previously associated with accumulation of evidence for a response, was affected by the presence of response conflict. These results shed light on the neural mechanisms that support decision making in the presence of conflict, a cognitive operation fundamental to both basic survival and high-level cognition.

(ProQuest: ... denotes formulae omitted.)

Cognitive control, or the capacity to modulate or manipulate bottom-up neural processes in the pursuit of high-level goals, is a central feature of high-level cognition. Cognitive control is often essential for decision making in a complex environment and is especially important whenever features of the environment pose challenges to the achievement of a goal. Response conflict and stimulus conflict, both of which demonstrate the need to select between competing representations, are two such challenges. We present here a novel fMRI experiment designed to examine both response conflict and stimulus conflict during perceptual decision making.

Response conflict occurs when simultaneous neural signals support competing response alternatives. It is hypothesized that the presence of response conflict leads to the engagement of top-down cognitive control (Botvinick, Braver, Barch, Carter, & Cohen, 2001; Kerns et al., 2004). In particular, fMRI studies point to a role for the dorsal anterior cingulate cortex (dACC) in the detection of response conflict (Carter et al., 1998), and to the dorsolateral prefrontal cortex (DLPFC) in its resolution (Egner & Hirsch, 2005; Kerns et al., 2004; MacDonald, Cohen, Stenger, & Carter, 2000).

In contrast to response conflict, stimulus conflict occurs when the presence of task-irrelevant perceptual information has a negative impact on the processing of taskrelevant perceptual information (Kornblum, 1994). Thus, stimulus conflict increases with the increasing perceptual strength of task-irrelevant information. Conversely, stimulus conflict should increase with the decreasing perceptual strength of task-relevant information, since in this case reduced perceptual strength is associated with reduced robustness to interference. As is the case with response conflict, stimulus conflict can lead to the engagement of top-down control processes that serve to limit its negative impact on performance (Egner, Delano, & Hirsch, 2007; Verbruggen, Notebaert, Liefooghe, & Vandierendonck, 2006).

Recent imaging studies of stimulus conflict, and other forms of nonresponse conflict, have yielded mixed results. One study involved a letter flanker task, in which multiple letters were mapped to each response option, and stimulus conflict (but not response conflict) was said to be present when the flanker and distractor were different letters that mapped to the same response (van Veen, Cohen, Botvinick, Stenger, & Carter, 2001). …

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