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, ventral regions of the basal ganglia play a key role in reward and reinforcement1-3 and are important in the development of addictive behaviors and habit formation.4-6 More central basal ganglia areas are involved in cognitive functions, such as procedural learning and working memory tasks.7 Importantly, diseases of the basal ganglia are not only linked to neurological disorders, but also psychiatric illnesses, including schizophrenia, drug addiction, depression, and obsessive-compulsive disorder. Thus, the role of the basal ganglia in cognitive and emotional behaviors is now as well accepted as its role in motor control.
