29 terms

Ch. 5 Motor Control Theories

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What is a Theory?
In the behavioral sciences, which include the study of human motor control and learning, theories focus on explaining human behavior. When the human behavior of interest is the performance and learning of motor skills, we look to theories to provide us with explanations about why people perform skills as they do, which means identifying that variables that account for the performance characteristics we observe. A good theory should describe and provide explanations for a large class of observable events.
Motor Control Theory
should describe and explain how the nervous system produces coordinated movement such that we are able to successfully perform a variety of motor skills in a variety on environmental contexts. Two essential issues important to a theory of motor control: the meaning of the term coordination as it applies to motor skill performance, and the "degrees of freedom problem."
Coordination
the patterning of head, body, and/or limb motions relative to the patterning of environmental objects and events.
Degrees of Freedom
the number of independent elements or components in a control system and the number of ways each component can act
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.
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.
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.
Differences Between the Systems
A closed-loop system involves feedback, whereas an open-loop does not. In the open-loop system, because feedback is not used in the control of the ongoing movement, the instructions contain all the information necessary for the effectors to carry out the planned movement. Although feedback is produced and available, it is not used to control the ongoing movement. In the closed-loop systems, the movement instructions are different. The control center issues initial instructions that is sufficient only to initiate the movement. The actual execution and completion of the movement depend on feedback information that reached the control center.
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.
Motor Program
a memory representation that stores information needed to perform an action.
Schmidt's 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.
Invariant Features
a unique set of characteristics that defines a GMP and does not vary from one performance of the action to another. These movement-related features form the basis of what Schmidt referred to as the fundamental pattern of the class of actions.
Fundamental Pattern of the Class of Actions
These features remain consistent from one performance of an action to another.
Movement Specific Parameters
These are movement-related features of the performance of action that can be varied from one performance to another; the features of a skill that must be added to the invariant features of a GMP before a person can perform a skill to meet the specific movement demands of a situation.
Relative Time
the proportion, or percentage, of the total amount of time required by each component of a skill during the performance of that skill
Schmidt's Schema Theory
A formalized theory of how GMP operates to control coordinated movement in Schmidt's schema theory. The Schema theory provides an explanation for how well a person can adapt to new situations or environmental contexts.
Schema
A rule or set of rules that serves to provide the basis for a decision; in Schmidt's schema theory, an abstract representation of rules governing movement.
GMP-Control Component
The control mechanism responsible for controlling the movement coordination patters of classes of actions, such as throwing, kicking, walking and running.
Motor Response Schema
responsible for providing the specific rules governing the performance of a skill in a given situation. Thus, the motor response schema provides parameters to the GMP.
Testing the Invariant Relative-Time Feature
Many experiments investigating several different skills (typing, handwriting, prehension). Researchers typically have investigated relative time invariance by observing changes in relative time across a range of values of an associated parameter, such as overall duration or speed. Their hypothesis was that if relative time is invariant for the generalized motor program involved in controlling walking and/or running gait patterns, then the percentages for a specific gait component should remain constant across the different speeds.
Dynamic Pattern Theory
An approach to describing and explaining the control of the 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.
Nonlinear Behavior
a behavior that changes in abrupt, nonlinear ways in response to systematic linear increases in the value of a specific variable (e.g. the change from smooth to turbulent water flow in a tube at a specific increase in water velocity; the change from a walking to a running gait at a specific increase in gait velocity).
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.
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
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 (e.g. relative phase); known also as collective variables
Control Parameters
coordinated movement control variables (e.g. tempo, or speed, and force) that freely change according to the characteristics of an action situation. According to the dynamic pattern view of motor control when a control parameter is systematically varied (e.g. speed is increased from slow to fast), an order parameter may remain stable or change its stable state characteristic at a certain level of change of the control parameter.
Self- Organization
the emergence of a specific stable pattern of behavior due to certain conditions characterizing a situation rather than to a specific control mechanism organizing the behavior; for example, in the physical world hurricanes self-organize when certain wind and water temperature conditions exist.
Coordinative Structures
Functionally specific collections of muscles and joints that are constrained by the nervous system to act cooperatively to produce an action; sometimes referred to as muscle, or motor, synergies.
Perception- 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; that is, the coordination of the visual perception of the object and the limb movement required to achieve the action of the goal.
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