A Qualitative Discussion of Mechanisms of Feedback and Feedforward in the Control of Locomotion

A brief discussion of the kinematics and dynamics of biped locomotion is provided. A number of elementary control problems are presented that include breaking or making contact with the environment, in addition to the conventional reflex and point-to-point movements. For this class of control problems, available mathematical methods of maintaining or breaking the support are surveyed, and these results are expressed in the context of experimental tests and results about the functional role of the support forces in stability and the role of skin mechanoreceptors in sensing and processing of these forces. The existence, role, and source of a network of gain controlling mechanisms??the facilitatory-inhibitory system??is reviewed. A gross locomotion model of the central nervous system is presented where the extrapyramidal pathway is modeled with a kinematic model, an inverse system, and a feedback system. These three subsystems correspond, respectively, to the lateral cerebellum, the basal ganglia, and the vermal and/or paravermal cerebellum.