Historical review of research on functions of basal ganglia.

Basal ganglia have been known as a motor center because their lesions cause motor disturbances in involuntary movements such as chorea, ballism or akinesia in parkinsonism. The different types of involuntary movements are closely related to the underlying muscle tone. Mechanisms of bradykinesia or akinesia have been elaborated in physiological studies on Parkinson's disease and the significance of sensorimotor processing or attention arousal has been disclosed as a relevant factor of bradykinesia. Analysis of short-stepped gait, frozen gait or apraxia of gait, has claimed the frontal lobe and the striatum to be a locomotion center especially in humans (bipedal locomotion). Cognitive function of the basal ganglia has attracted attention particularly in the disorder of Parkinson's disease. Subcortical dementia, difficulty in formation or changes of concepts are encountered in advanced stages of Parkinson's disease. Whether cognitive functions in the frontostriatal system are primarily related to the motor function of the brain is an issue for future study.