Neuroimaging of Executive Processing

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DESCRIPTION (provided by applicant): Executive processes facilitate the flexible, top-down control of human behavior. A network of brain regions including prefrontal cortex (PFC), anterior cingulate cortex, and parietal cortex is thought to be central for executive processing. Neuroimaging and lesion studies have suggested that these regions play a role in selection or potentiation of behavior based upon context. The experiments detailed in this proposal will use functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms of response selection, evaluation of feedback and rewards, and the goal-directed control of behavior. This proposal has three specific aims. First, it seeks to elucidate the role of dorsolateral PFC (dlPFC) in behavioral control, to test the hypothesis that executive functions potentiate sets of stimulus-response contingencies rather than responses themselves. The proposed experiments manipulate the amount of information each stimulus in a sequence contributes either to learning a decision rule or to preparing a needed response. Second, it investigates the role of ventromedial PFC (vmPFC) in the potentiation of contingencies between responses and rewards. The proposed experiments manipulate the reward expectation associated with different stimuli and with responses at different points in time, to test the hypothesis that vmPFC supports the resolution of uncertainty about reward-response links. Third, it investigates the interaction between prefrontal systems by examining the influence of reward uncertainty upon decision processes. Some stimuli are associated with uncertainty in future rewards, while others are associated with certain outcomes. The experiments test the hypothesis that increasing activity in vmPFC reward systems results in decreased activity in dlPFC control systems. The proposed research program will have a significant impact upon the understanding of human executive processing, including selection, decision, and working memory components. A better understanding of these processes will lead to further improvements in clinical remediation of neurological and psychiatric disorders characterized by impairments in executive function or behavioral selection (e.g., frontal lobe damage, schizophrenia, Parkinson's disease).