How movement is guided

The development of a theory of prospective guidance of movement general tau theory is described. The theory deals with the purposive guidance of bodily movements, including internal movements, by means of the patterns of flow in sensory arrays and the patterns of flow of electrical energy within the nervous system. The central idea is that movement is guided by tau-coupling action-gaps. All purposive movement of the body, and within the body, requires guided closure of action-gaps. An action-gap, generally defined, is the changing gap between a current state and a goal state. Examples are the distance action-gap between the hand and an object when reaching, the optical action-gap between the images of the hand and object in the optic flow-field, the suction action-gap when a baby is drawing in milk, the pitch action-gap when a singer is sliding between notes. Tau of an action-gap is the first-order time-toclosure of the action-gap, i.e., the current size of the action-gap divided by its current rate of closure. Tau-coupling means keeping the taus of two action-gaps in constant ratio during a movement. Theoretical analyses and experiments are summarized that offer explanations, through the tau-coupling of action-gaps, of how the taus of actiongaps are sensed, how patterned electrical activity in the brain guides movement, how space is action-scaled, how actions are fitted into available spatio-temporal slots, how a driver controls braking and steering, how infants guide their movements, how athletes guide their movements, how musicians create expression by the way they guide their movements. Applications of the theory to the diagnosis and treatment of movement disorders are also discussed.