The mysterious motor function of the basal ganglia

I greatly appreciate the honor you have bestowed by inviting me to give this year’s Robert Wartenberg Lecture, and I would like to take the opportunity to thank my many friends and colleagues in the American Academy of Neurology for their unfailing hospitality and kindness on every occasion that I have visited your continent. Although I never had the pleasure of meeting Robert Wartenberg, curiously, he had a profound influence on my decision to enter neurology. The late Professor Dai Davies, professor of anatomy at St. Thomas’ Hospital Medical School, sensing my interest in the nervous system, lent me his personal copies of Wartenberg’s Examination of Reflexes, Gordon Holmes’ second edition of Introduction to Clinical Neurology, and Wilder Penfield and Theodore Rasmussen’s Cerebral Cortex of Man. At that stage, in the late 1950s, I stepped sideways from the mainstream of medical education into the research laboratory to try to discover why the substantia nigra was black! In my naivete, I thought that this must constitute some clue to the function of this region of the brain, and I even believed, and still do believe, that neuromelanin holds the key to the cause of Parkinson disease. My interest in the basal ganglia was born then and persisted ever after. Naturally I have been led, as many were before, to seek the functions of this mysterious region of the brain. Kinnier Wilson,’ in his Croonian Lectures of 1925, was forced to conclude that “the ganglia situated in the base of the brain still, to a large extent, retain the characteristic of basementsviz. , darkness. ” What light has been shed over the next 75 years into these dark basements of the brain? Stimulated by the discovery of the importance of dopamine in Parkinson disease, the last decade has witnessed an explosion of research into all aspects of basal ganglia activity. Neuroscientists from many disciplines, all bringing individual skills and philosophies to bear on the problem, have speculated on their function. The classical clinician’s view, based on Kinnier Wilson’s2 discovery of the disease that bears his name and on the careful clinicopathologic correlation that followed, that this region is part of the motor system, has been attacked as narrow-minded. Some physiologists and psychologists, impressed by the wealth of input from virtually all areas of the cerebral cortex into the basal ganglia, have speculated that these regions may exert much wider functions in sensory and “cognitive” domains as well as in the motor sphere. I intend to examine that thesis in the light of clinical evidence. My conclusion is that, as far as that evidence goes, the basal ganglia should still be regarded as organs of motor control. The next question is, what do the basal ganglia contribute to motor organization? Again, I will tackle the problem from the standpoint of clinical evidence to conclude with the hypothesis that the basal ganglia are responsible for the automa= execution of learned motor plans. What clinical material gives the clue t o normal basal ganglia function? Based on present anatomic knowledge, I believe that Parkinson disease comes closest to providing evidence on the consequences