Chapter 4 Motor Control Theories Concept: Theories about how we control coordinated movement differ in terms of the roles of central and environmental features of a control system

Theory and Professional Practice What is theory? Accurately describes a large class of observations Make definite predictions about results of future observations (Hawking, 1996) With motor learning and control, theories focus on: Explaining human behavior Providing explanations about why people perform skills as they do Identifying variables through observations of these performances

Motor Control Theory Describes and explains how the nervous system produces coordinated movement of motor skill in a variety of environments Two issues of importance: Coordination Degrees of freedom

Coordination Patterning of body and limb motions relative to the patterning of environmental objects and events (Turvey, 1990) Two parts to consider: Movement pattern of a skill in relationship at a specific point of time Context of the environment of the head, body, and/or limb movements so the actions can be accomplished

Degrees of Freedom Number of independent elements in a central system and the ways each component can act Degree of Freedom problem: Control problem Occurs in the designing of a complex system that produces a specific result Involves determining how many degrees of freedom is required to produce the result

Open Loop and Closed Loop Systems Models of basic descriptions that show the CNS and PNS initiate and control action Each has a central center (executive) Executive generates and issues movement instructions to effectors (muscles/joints) Both also contain movement instructions from control center to effectors

Differences Between the Systems Open Loop Does not use feedback Control center provides all the information for effectors to carry out movement Closed Loop Uses feedback Control center issues information to effectors sufficient only to initiate movement Two differences

Two Theories of Motor Control 1. Motor Program-based theory: memory-based construct that controls coordinated movement 2. Dynamic Pattern theory, a.k.a. Dynamic Systems: approach to describing and explaining the control of coordinated movement that emphasize the role of information in the environment and properties of the body/limbs

Motor Program-Based Theory Based on the work of Richard Schmidt (1988) Hypothesized generalized motor program: mechanism accounting for adaptive and flexible qualities of human movement Proposed that generalized motor program controls class of actions vs. specific movement

Motor Program-Based Theory, cont’d These “invariant factors” are the signatures of the generalized motor program (does not vary from one performance to another) Parameters are specific movement features that can vary from one performance of a skill to another

Schmidt’s Schema Theory Schema: rules that serve to provide the basis for a decision based from related experiences Described two control components: Generalized motor program – control mechanism responsible for controlling a class of actions, i.e., kicking Motor response schema – responsible for providing the specific rules governing an action in a given situation

Schmidt’s Schema Theory, cont’d This theory explains how a person can adapt to new situations or environmental contexts Solves the degree of freedom problem

Dynamic Pattern Theory (a.k.a., Dynamical Systems) Describes the control of coordinated movement that emphasizes the role of information in the environment and dynamic properties of the body/limbs Seen from the perspective of nonlinear dynamics (behavioral changes are abrupt)

Stability and Attractors Stability: behavioral steady state of a system Attractors: stable behavioral steady states of systems Preferred behavioral states Energy efficient states

Order and Control Parameters Order parameter Called collective variables Functional specific and abstract variables that define the overall behavior of the system Enable a coordinated pattern of movement that can be reproduced and distinguished from other patterns Relative phase is the most prominent of order parameters which represents the movement relationship between two movement segments

Order and Control Parameters, cont’d Control parameter Variable, when increased or decreased, will influence the stability and character of the order parameter Is important to identify since it becomes the variable to manipulate in order to assess the stability of the order parameter Provides the basis for determining attractor states for patterns of limb movement

Order and Control Parameters, cont’d Self-Organization When certain conditions characterize a situation, a specific pattern of limb movement emerges This pattern of movement self- organizes within the characteristic of environmental conditions and limb dynamics

Coordinated Structures Functional synergies of muscles and joints of a person’s nervous system which act cooperatively to produce an action Develops through practice, experience, or naturally Can be intrinsic (walking) or developed through practice

Perception and Action Coupling Dynamic pattern theory Essential element in accounting for skillful performance of open skills The perception part of the interaction detects and uses critical invariant information in the environment

Perception and Action Coupling, cont’d The action part involves the setting and regulating of movement control features that enable action goal achievement For example, Greek letter “tau” (  )

Present State of the Control Theory Issue Motor program-based theory and dynamic pattern theory are the predominant behavioral theories addressing how the nervous system produces coordinated movement Theory of control cannot focus exclusively on the movement information that is specified by the CNS

Present State of the Control Theory Issue, cont’d Task and environmental characteristics must be taken into account (Newell, 1986) Speculation of hybrid on a compromise theory could emerge, to explain the control of coordinated movement

Chapter 4 Motor Control Theories