The organization of basal ganglia circuitry is best appreciated within the context of frontal cortical organization. The basal ganglia and frontal cortex operate together to learn optimal behavior policy and to execute goal-directed behaviors. This requires not only the execution of motor plans, but also the behaviors that lead to this execution, including emotions and motivation that drive behaviors, cognition that organizes and plans the general strategy, motor planning, and finally, the execution of that plan. The components of the frontal cortex that mediate behaviors, including the motivation and emotional drive, coupled with the planning and cognitive components to plan the action, and finally, the movement itself, are reflected in the organization, physiology, and connections between areas of frontal cortex and in their projections to the striatum. The frontal cortex can be divided into several general functional regions (Figure 2): the orbital and medial prefrontal cortex (PFC), involved in emotions and motivation; the dorsolateral PFC, involved in higher cognitive processes or “executive functions”; the premotor areas, involved in different aspects of motor planning; and motor cortex, involved in the execution
