The basal ganglia work in concert with the cortex, thalamus, and brain stem centers to orchestrate and execute planned, motivated behaviors requiring motor, cognitive, and limbic circuits. Historically, the basal ganglia are best known for their motor functions and their association with the neuropathology in the neurodegenerative disorders affecting the control of movement, such as Parkinson disease and Huntington disease. While a role for the basal ganglia in the control of movement is clear, our concept of basal ganglia function has dramatically changed in the last 40 years, from a purely motor or sensory-motor one to one of a more complex and complicated set of functions that mediate the full range of goal-directed behaviors. Thus, in addition to their involvement in the expression of goal-directed behaviors through movement, the basal ganglia are also involved in the processes that lead to movement—that is, the elements that drive actions, including emotions, motivation, and cognition. Indeed, regions within each of the basal ganglia nuclei have been identified as serving not only a sensory-motor function, but also limbic and cognitive ones as well. Overall,
