A New Look at the Organization of the Motor System

Abstract

Publisher Summary This chapter provides an overview on the organization of the motor system. The descending pathways from the cerebral cortex and the brain stem to the spinal interneurons and motor neurons must represent the instrument by which the brain steers movements of body and limbs. They are referred as the “motor system.” In earlier years, the motor system of the brain tended to be identified with the motor cortex. In human patients, destruction of the efferent pathways of the sensorimotor area produces a severe crippling motor defect known as hemiplegia. The corticospinal fibers are mainly derived from the sensorimotor areas and terminate predominantly contralaterally in the spinal gray. A striking parallel exists between the development of the corticomotoneuronal connections and the capacity to execute highly fractionated movements. Thus, in the rhesus monkey a bilateral pyramidotomy produces a flaccid paresis of the extremities especially of their distal parts combined with a paucity of independent extremity movements.