Executive processes play a central role in cognition. Although executive processes are difficult to define, there is general agreement that they are metaprocesses and that they include the following: (a) attention to task-relevant processes and inhibition of irrelevant processes or responses, (b) task-management, which includes switching among two or more known tasks, and planning subtasks in the correct temporal or logical order to satisfy an overall goal, (c) coding of contextual source information about an event, and (d) monitoring the current state of one's actions. There is also general agreement that these executive processes are mediated in large part by mechanisms of the prefrontal cortex, that portion of frontal cortex anterior to the motor regions. When patients have damage to these prefrontal mechanisms, their executive processes suffer dramatically. The proposed research program makes use of behavioral and fMRI studies of the first two of these executive processes, attention/inhibition and task-management. The research focuses on these two because they are at the core of discussion of executive processes and because they share a reliance on selective attention. The proposed research has three major aims: The first is to determine whether there are commonalities and differences between these two executive processes in behavioral and neural signatures. The second goal is to study the executive process of inhibition in detail. For this goal, we propose studies that should determine: (a) what brain circuitry is involved in attentional and inhibitory control, (b) how overt behavior and underlying neural circuitry differ for different sorts of inhibition, (c) whether the overt behavior and underlying circuitry depend on the content of the materials involved, and (d) whether there are systematic individual difference in inhibition both behaviorally and in the neural circuits involved. The third goal is to study task-management in detail by studying task-switching, an important component of task-management. The empirical studies in service of this goal will try to determine: (a) the basic circuitry involved, (b) changes in behavior and circuitry with changes in what has to be switched, (c) changes in behavior and underlying circuitry with the content of what is switched, and (d) whether there are systematic individual differences in task-switching that are correlated with neural differences. In addition to the experimental work, the research continues to develop a computational model for these executive processes that derives from the empirical results. Patients with frontal lesions who have deficits on one or another executive process will be studied.
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