Order and Disorder in the Motor System

Abstract

The problem of motor control is central to the contemporary neurosciences, especially to neurology, since it involves an understanding of the basic mechanisms of the function of the nervous system, and its relation to its environment. The brain, it is said, exists to provide effector interaction with the external world. The famous dictum of Aristotle: “Nihil est in intellectu quod non primus fuerit in sensu” serves to indicate the essentially subjective nature of enquiry into brain function, associated in European minds with the philosophy of Descartes, which was the received approach before the advent of the experimental method. It serves also, perhaps, to remind us how constrained even current research is in humans, despite the availability of newer methods of functional imaging and measurement. Ferrier (1876) regarded the human brain as possessing both sentient and active or motor functions, and did not clearly relate these to each other despite his insights into the role of the cerebral cortex in the initiation of movement. The stimulus for continued investigation of the problems posed in seeking understanding of motor control has largely derived from the need to seek alleviation of the disabilities suffered by patients with diseases of the brain. These disabilities have proven difficult to classify and to describe. Furthermore, the fragmentation of investigation that resulted from the separation of the neurosciences from clinical research has led to further confusion in understanding these problems. This separation was apparent relatively early in the development of concepts of motor control.