Stimulus and Response-Related Conflict Processing in the Human Brain




Fedota, John R.S.

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Cognitive control seeks to limit the conflict created by simultaneous activation of alternative cognitive representations. Conflict monitoring is theorized to be the first of a two-step cognitive control process. Conflicting representations activate control, which then mitigates the consequences of conflict through compensatory attentional allocations. While the current literature has localized these conflict monitoring processes to the medial frontal cortex, the types of conflict that activate the circuit remain unclear. The three experiments of this dissertation were designed to explore the relationship between conflict instantiated at different levels of information processing and the medial frontal cortex conflict monitoring circuit. The use of modified Eriksen flanker stimuli, psychophysically tuned to each participant, allowed for the controlled elicitation of both response conflict and stimulus uncertainty. By monitoring the behavioral and electrophysiological responses to both types of conflict during a given trial as well as on a trial-to-trial basis, these studies serve to better characterize both medial frontal cortex mediated conflict monitoring and visual cortex mediated attentional biasing. Results showed that stimulus uncertainty and response conflict have dissociable, but related effects on conflict monitoring processes. However, the sensitivity of conflict monitoring processes to stimulus uncertainty requires careful quantification of the amount of uncertainty instantiated, an aspect overlooked in prior studies. Trial-to-trial findings showed a relationship between response conflict processing and stimulus uncertainty processing such that prior exposure to either type of conflict facilitated the subsequent performance of a response conflict inducing task. This facilitation occurs via top-down influences on sensory processing following exposure to stimulus uncertainty. This modulation provides empirical evidence of a biologically plausible mechanism linking cognitive control and biased competition of attention allocation. In addition, these findings suggest a modification of current conflict monitoring theory to include multiple, related conflict monitoring sub processes as opposed to a single executive monitor. These results fit within the framework previously established that implicates the medial frontal cortex in higher-level decision tasks while expanding the empirical proof to lower-level cognitive processes as well as increasing the temporal resolution of the associated processing.



Conflict, Cognitive Control, Visual Attention