Although several new theories of general function have emerged from the enormous progress in understanding the anatomy, physiology, and behaviors associated with the basal ganglia,7-10 the actual role of the basal ganglia in executing goal-directed behaviors remains elusive. What is clear from the recent progress is that this set of subcortical nuclei work in tandem with the cortex (particularly the frontal cortex) via a complex cortico-basal ganglia network to develop and carry out complex behaviors. The concept of parallel cortico-subcortical channels through the basal ganglia has been prominent in how the field has viewed the organizational understanding of basal ganglia circuits.11 However, we now know that cortico-basal ganglia connections are more complicated and that interactions between functional territories are extensive.12-15 These two organizational schemes (separate functional channels and integration across function) probably work together, allowing the coordinated behaviors to be maintained and focused, but also to be modified according to appropriate external and internal stimuli. Indeed, both the ability to maintain and to focus on the execution of specific behaviors, as well as the ability to adapt appropriately to external
