Functions of the cortico-subthalamo-pallidal pathway

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The functional significance of the cortico-subthalamo-pallidal "hyperdirect" pathway has been investigated, and a dynamic "center-surround model" of basal ganglia function in the control of voluntary limb movements has been suggested. When a voluntary movement is about to be initiated by cortical mechanisms, a corollary signal conveyed through the "hyperdirect" pathway first inhibits large areas of the thalamus and cerebral cortex that are related to both the selected motor program and other competing programs. Then, another corollary signal through the cortico-striato-pallidal "direct" pathway disinhibits their targets and releases only the selected motor program. Based on this model, akinesia observed in Parkinson disease could better be explained by reduced disinhibition in the thalamus and cortex through the "direct" pathway in the spatial and temporal domains. Amelioration of akinesia after subthalamic lesion could also be understood by restored disinhibition in the thalamus and cortex.