Frontal Striatal Systems and Dopamine in Normal and Pathological Behavior

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Our lab uses a combination of neurophysiology, pharmacology and functional imaging to examine the role of frontal striatal systems in behavior. Several of our experiments are motivated by studies in patient groups that show that patients have deficits on particular tasks. We then study those tasks in the lab to delineate the neural circuits that underlie the behaviors, as well as how brain areas within those neural circuits interact to drive the behavior. Recent work has focused on understanding the mechanisms that drive the choice of novel options in decision making tasks. We use tasks in which participants select particular options and learn the reward properties of each of those options. We then introduce novel choice options at stochastic intervals. We have found that increasing dopamine levels, by blocking dopamine reuptake, can increase preference for novel options. We have also found that the amygdala plays a role in preference for novel objects, in combination with orbital frontal cortex and the ventral striatum. In related experiments in the lab, we have been studying action selection, when actions must be selected under different rules. We have found that both lateral prefrontal cortex and the dorsal striatum play a role in this process. Further, lateral prefrontal cortex appears to select actions before the dorsal striatum, when actions are selected on the basis of immediately available information. When actions have to be selected on the basis of past outcomes, however, the dorsal striatum appears to play a more important role. Thus, these two interconnected brain structures appear to play complimentary roles in selecting actions.