Motor Control and Motor Learning: The Closed-Loop Perspective
George E. Stelmach
University of Wisconsin
The information-processing approach to motor control and learning discussed in Chapter 3 provides a conceptual framework in which to study and understand human performance but does not adequately account for the coordination and regulation of movement. Superficially, the coordination of appropriate muscular commands for a specified movement appears to be a relatively simple task, yet the successful completion of a refined motor act requires a high degree of temporal precision among the motor commands for the agonist and antagonist muscle groups. Questions and controversies concerning how we control our limbs during movement execution have stimulated neurophysiological and psychological inquiry for many years. Perhaps it is helpful to begin our discussion by defining the various theoretical views in which motor control has been characterized or explained. The first--and until recently--favored position claimed the reporting and updating of information about the present state of the organism via peripheral receptors (feedback) to be necessary for the control of intentional, coordinated movement. With such information the organism is operating in a closed-loop fashion and thus is capable of detecting errors and correcting them. The opposing position contends that movement is regulated by central rather than peripheral sources, operating in an open-loop mode, as it were. In such a framework the information generated from central sources to specify movement is purportedly sufficient for the control of movement. The controversy existing between open- and closed-loop modes of control has dominated the motor behavior literature for many years (see Kelso & Stelmach, 1976, for review).