Studies of Hierarchic Organization in Prefrontal Cortex

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DESCRIPTION (provided by applicant): PFC mediated cognitive control processes permit flexible behavior by biasing selection of goal-relevant responses. The research proposed here seeks to test two related hypotheses regarding the organization of RFC control processes. A functional magnetic resonance imaging (fMRI) study will identify regions of RFC processing different levels of representation en route to selecting a response. These levels are hypothesized to be individuated on the basis of the abstractness of the representation guiding selection, ranging from concrete features (e.g., red) in premotor cortex, to more abstract dimensions (e.g., color) in posterior lateral regions, to a general goal or context (e.g., color naming task) in frontal pole. Subsequently, a study of neurological patients with focal damage in RFC and a study of focal disruption by transcranial magnetic stimulation (TMS) will test the functional necessity and independence of these RFC regions. Furthermore, these data, along with functional connectivity analysis of the fMRI data, can test the hypothesis that this representational hierarchy is reflected in the relationship among RFC regions, instantiated in a flow of processing from superordinate to subordinate regions. Basic knowledge gained regarding the organization of RFC can provide important insights into disorders impacting the frontal lobes and toward the development of directed clinical assessments that index executive function.