Physiology of motor control in man.

The physiology of motor control is considered in hierarchical terms. In that way it is possible to gain insight into the complex superimposed systems of motor control. In the execution of a voluntary movement the neural machinery is called into operation at all of the hierarchical levels: (1) the motor unit; (2) spinal reflex mechanisms; (3) brain stem mechanisms; (4) cerebellar vermis controls; cerebrocerebellar controls, (5) via the pars intermedia and (6) via the cerebellar hemispheres and also of the basal ganglia. At level 6 there is design for reverberatory loop operation within the association cortex and with the subcortical structures, which gives opportunity for preprogramming movements by motor memories. This is especially important for ballistic movements that are too fast for updating by feedback from the periphery. Reverberatory loop operation both within the neocortex and with cortico-subcortical circuits presumably is occurring during the readiness potential preceding a voluntary movement.