Chapter 5Motor Control Theories

Concept:Theories about how we control coordinated movement differ in terms of the role of central and environmental features of a control system

Theory and Professional Practice

What is a theory?

It helps us understand phenomena and explains the reason why these phenomena exist or behaves as they do.

Theory and Professional Practice

Stephen Hawking

It must accurately describe a large class of observations

It must make definite predictions about the results of future observations

Theory and Professional Practice

The relevance of Motor Control Theory for the Practitioner

Provides a base of support on which he or she can develop effective skill instructions and practice environments

Motor Control Theory Two essential issues important to a

theory of motor control

Coordination Degrees of freedom problem

Motor Control Theory Motor Control Theories-behavioral

Explain observed behavior without attempting to specify neural-level features of the control process

Propose laws and principles that govern coordinated human motor behavior

Coordination The patterning of head, body, and/or

limb motions relative to the patterning of environmental objects and events.

Coordination There are two parts to the definition

Patterns of head, body and limb movements

The organizational relationship of movement characteristics of the head, body, and limb involved in the performance, regardless of the skill level of the performer.

Coordination There are two parts to the definition

Relative to the pattern of environmental objects and events

movement coordination in relation to the context in which the skill is performed

Coordination Example..

When walking, people must adapt their head, body and limb movement patterns to the characteristics of the pathway.

The Degrees of Freedom Nicolai Berstein

Russian physiologist The nervous system had to solve

what he termed the “degrees of freedom problem.”

The Degrees of Freedom The number of independent elements of

components in a control system and the number of ways each component can act

Each element is “free” to vary in specific way

Example: the elbow joint can flex and extend

The Degrees of Freedom Degrees of freedom problem

a control problem that occurs in the designing of a complex system that must produce a specific result; the design problem involves determining how to constrain the system’s many degrees of freedom so that it can produce the specific result.

The Degrees of Freedom Example:

Picking up a glass from a table How many joints are involved

shoulder 1elbow 1wrist 1

fingers (3 joints x 4) 12 thumb 3

The Degrees of Freedom

It becomes evident that for any motor skill, the control problem involved in enabling a person to perform that skill is an enormous one.

Open-Loop and Closed-Loop Control Systems Open-loop control system

a control system in which all the information needed to initiate and carry out an action as planned is contained in the initial instructions to the effectors

Open-Loop and Closed-Loop Control Systems Closed-loop control system

a system of control in which during the course of an action, feedback is compared against a standard or reference to enable an action to be carried out as planned

Open-Loop and Closed-Loop Control Systems Differences between the systems Feedback

information from the sensory system that indicated the status of a movement to the central nervous system; in a closed-loop control system, feedback is used to make corrections to an ongoing movement.

Open-Loop and Closed-Loop Control Systems Difference between the systems Movement Instructions

Instructions issued by the control center to the effectors to carry out the planned movement.

Open-loop-contain all the information necessary

Closed-loop-the actual execution and completion of the movement depend on feedback information that reaches the control center.

Two Theories of Motor Control Motor Program-Based Theory

Gives prominence to movement instructions specified by the central nervous system

Dynamic Pattern Theory Gives more influence to movement

instructions specified by the environment and to the dynamic interaction this information with the body, limbs, and nervous system.

Motor Program-Based Theory

Motor program A memory representation that stores

information needed to perform an action

Motor Program-Based Theory Richard Schmidt proposed..

That a serious problem with previous views was that they limited the motor program to controlling specific movements or sequence of movements

Motor Program-Based Theory Richard Schmidt Generalized motor program (GMP)

The memory representation of a class of actions that share common invariant characteristics; it provides the basis for controlling a specific action within the class of actions

Motor Program-Based Theory Generalized motor program (GMP)

Invariant featuresthe fundamental pattern of the class of action and does not vary from one performance of the action to another

Parametersfeatures that can be varied from one performance of a skill to another to meet the specific movement demands of a situation

Motor Program-Based Theory Schmidt’s schema theory

SchemaA rule of set of rules that serves to provide the basis for a decision; in Schmidt’s schema theory, an abstract representation of rules governing movement

Motor Program-Based Theory Schmidt used the schema concept to

describe two control components involved in the learning and control of skills

Motor Program-Based Theory First component…

The generalized motor program is the control mechanism responsible for controlling the general characteristics of classes of action, such as throwing, kicking, walking, and running

Motor Program-Based Theory Second component…

The motor response schema is responsible for providing the specific rules governing an action in a given situation. Thus, the motor response schema provides parameters to the generalized motor program.

Dynamic Pattern Theory

An approach to describing and explaining the control of coordinated movement that emphasizes the role of information in the environment and the dynamic properties of the body and limbs; it is also known as the dynamical systems theory

Dynamic Pattern Theory

Sees human movement control as a complex system that behaves in ways similar to those of any complex biological or physical system

Human motor control is seen from the perspective of nonlinear dynamics

Dynamic Pattern Theory Stability

A behavioral steady state of a system that represents a preferred behavioral state and incorporates the notion of invariance by noting that a stable system will spontaneously return to a stable state after it is slightly perturbed

Dynamic Pattern Theory Attractors

The stable behavioral steady states of systems. In terms of human coordinated movement, attractors characterize preferred behavioral states, such as the in-phase and antiphase states for rhythmic bimanual finger movements.

Dynamic Pattern Theory Order Parameters

Functionally specific variables that define the overall behavior of a system; they enable a coordinated pattern of movement to be reproduced and distinguished from other patterns; known also as collective variables.

Dynamic Pattern Theory Control Parameters

Coordinated movement control variables (e.g., tempo, or speed, and force) that freely change according to the characteristics of an action situation.

Dynamic Pattern Theory Self-organization

The emergence of specific stable pattern of behavior due to certain conditions characterizing a situation rather than to a specific control mechanism organizing the behavior

Dynamic Pattern Theory Coordinative structures

Functionally specific collectives of muscles and joints that are constrained by the nervous system to act cooperatively to produce an action.

Dynamic Pattern Theory Coordinative structures

Intrinsic coordinative structures are involved in actions such as walking, running, and bimanual coordination.

The muscles and joints of the limbs have a natural tendency to demonstrate interlimb coordination patterns that have characterized our performance since early in life.

Dynamic Pattern Theory Coordinative structures

In contrast, coordinative structures developed through practice become new combinations of muscles and joints that act together to produce a coordination pattern that will allow the achievement of an action goal.

Dynamic Pattern Theory Perception and action coupling

The spatial and temporal coordination of

vision and the hands or feet that enables

people to perform eye-hand and eye-foot

coordination skills.

The Present State of the Control Theory Issue

A theory of control cannot focus exclusively on the movement information that is specified by the central nervous system. Theorists must take task and environmental characteristics into account.

The Present State of the Control Theory Issue

Some researchers would prefer to see a compromise between the two theories, which would lead to the development of a hybrid theory that incorporates the strengths of each theory.

The Present State of the Control Theory Issue

Abenethy and Sparro speculated that a compromise theory was unlikely because the two theories represent two vastly different approaches to explaining the control of coordinated movement.

Questions…..