A fundamental challenge in cognitive neuroscience involves the identification of the mechanisms that allow the flexible, goal-directed behavior that characterizes human performance. Our previous work has led to a theory regarding the role of prefrontal cortex (PFC) in guiding behavior in accord with internally represented goals and intentions. Central to this guided activation theory of PFC is the hypothesis that PFC actively maintains goal representations that guide activation in posterior structures responsible for executing task-relevant behavior. This project has two specific aims. First, we will attempt to further our understanding of the rich, interactive dynamics between PFC representations and activity in posterior cortex. In particular, we will try to find support for our claim that PFC representations modulate task processing in posterior cortex in a continuous and direct fashion. Second, we will examine the mechanisms involved in the flexible updating of PFC goal representations in response to cues in the environment. We propose that the medial temporal lobe may play a crucial role in the forming of episodic associations between environmental cues and task goals that are used to establish effective goal representations in PFC. We will study these issues within the context of the task-switching paradigm, an experimental framework that is ideally suited to our purposes because it entails the repeated establishment and shifting of goal representations needed to guide behavioral responses to ambiguous stimuli. We will develop computational models with the aims of (i) demonstrating the power of the guided activation theory of PFC in explaining a wide variety of phenomena reported in the task-switching literature; and of (ii) generating detailed empirical predictions regarding the neurobiological components underlying the functions of interest here. In parallel, we will conduct a series of fMRI and ERP studies to test these predictions, often contrasting them with predictions made by competing theories. Successful execution of this project will result in a much more detailed understanding of the neural mechanisms underlying cognitive control. Importantly, our models may serve as a much desired foundation for more rational approaches to research on the disturbance of these mechanisms in neuropsychiatric disorders, such as schizophrenia, depression, and addiction, all of which are known to be associated with disruptions of cognitive control.
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