[Functions of direct, indirect and hyperdirect pathways]

The 'direct and indirect pathways model' that was proposed almost 20 years ago revolutionarily changed our understanding of the basal ganglia and was successful in explaining certain aspects of the pathophysiology of movement disorders. However, many evidences and results that contradict this model have emerged during the last decade. In this article, I will introduce the 'cortico-subthalamo-pallidal hyperdirect pathway' that has become a focus of attention recently and discuss the functions of the basal ganglia with the emphasis on the following four topics: first, effectiveness and limitations of the classical 'direct and indirect pathways model'; second, focused selection of movements and motor learning; third, firing rate model versus firing pattern model on the pathophysiology of movement disorders; and lastly, mechanisms of stereotaxic surgery.