Motor Systems, with Specific Reference to the Control of Locomotion

Abstract

The central nervous system (CNS) must produce specific patterns of motor neuron impulses during a coordinated movement. The desire to understand how these patterns are produced and controlled has led investigators to examine the properties of interneurons within the CNS. A set of theoretical principles has emerged from these studies that are applicable to both invertebrates and vertebrates (Wilson 1967, Evarts et al 1971, Gurfinkel & Shik 1973, R. B. Stein et al 1973, Grillner 1975, Herman et al 1976, Shik&Orlovsky 1976, Wetzel & Stuart 1976, P. S. G. Stein 1977). This review will discuss how these principles apply to locomotion and will demon­ strate that they may also serve as useful working hypotheses in the study of other motor systems. The central hypothesis is that there is a neural pattern generator residing within the CNS that serves to produce the basic motor program (Wilson 1972). Informa­ tion derived from sensory input may modify the output of the pattern generator so that the motor output is adapted to the particular mechanical properties of the organism and its environment. The principles are the following: