Behavioral Theories of Motor Control

1
Behavioral Theories of Motor Control

• Chapter 3

2
Overview

• Now that weve looked at response preparation,
  what happens during the response programming
  stage?

3
Early Motor Program Theories

• Proposed that for each movement to be made, a
  separate motor program existed and was stored in
  memory
• Two problems
• Storage Hard drive (brain) could run out of
  space
• Novel responses How do you respond to an action
  never done before?

4
Command Center

• Decisiongt appropriate plan retrieved from memorygt
  instructions to rest of body for action

5
Open Loop Systems

• Open loop
• Action plans generated by command center then
  carried out by the limbs and muscles without
  modification

Action
Command Center
Mechanical ExampleSending Email
6
Closed Loop Systems

• Closed loop
• Command center generates action plan that
  initiates the movement
• Feedback is used to modify on-going action

Action
Command Center
Feedback
Mechanical Example Thermostat
7
Slow Vs. Rapid Movements

• Motor control uses both open and closed loop
  systems
• Movements are planned in advance, initiated
  executed with little modification (remember the
  fake in PRP?)
• If a rapid movement, feedback will be used for
  the next attempt
• For slower movements, open loop begins the
  movement and closed loop will continue to
  completion

8
Problem

• How does a person do a novel motor skill?
• Motor Program
• Abstract representation of a movement plan
• Stored in memory
• Issues instructions that are carried out by the
  limbs and muscles

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Generalized Motor Program (GMP)

• Represents a class of actions or pattern of
  movement that can be modified to yield various
  response outcomes
• Invariant features
• Relatively fixed underlying features that define
  a GMP
• Parameters
• Flexible features that define how to execute a GMP

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Fixed vs. Flexible Features

• Write your name with the following
• Your dominant hand
• Your non-dominant hand
• Pen in your mouth
• Pressing very hard
• Pressing very soft
• Write quickly, then slowly
• Which aspects were fixed? Flexible?

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Invariant Features

• Relatively fixed underlying features
• Sequence of actions or components
• Relative timing
• Internal rhythm of the skill the amount of time
  to write each letter of your name will stay the
  same whether writing fast or slow
• Relative force
• Internal force relationship The amount of force
  given to write each letter stays proportionally
  the same whether pressing hard or soft

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Parameters

• Adaptable features of program
• Easily modified from one performance to another
  to produce variations of a motor response
• Overall duration Fast or slow
• Overall force Hard or soft
• Muscle selection Writing with hand or foot?

13
Review Question

• When swimmers use hand paddles or when baseball
  hitters swing heavier bats, does this manipulate
  invariant features or parameter features?
• When might such an action hinder the development
  of correct technique?
• What signs would you look for to avoid this
  problem?

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Schema

• Rule or relationship that directs decision-making
  when a learner is faced with a movement problem
• Developed by abstracting 4 sources of information
  for each performance attempt
• Initial conditions present at start of movement
• Response specifications parameters used in the
  execution of the movement
• Sensory consequences what did the action feel
  like?
• Response outcome how successful was the response?

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Schema Development

• For each movement attempt the four sources of
  information are stored in memory briefly
• Feedback from the attempt verifies
• How successful was the performance?
• Do I need to change the movement?
• With each additional attempt, the strength of the
  schema increases when you compare one attempt to
  the next

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Motor Response Schema

• Recall schema
• Responsible for organizing the motor program
• What do I need to do?gtWhat conditions exist?gtWhat
  parameters invariant features are
  required?gtExecute the response
• Recognition schema
• Responsible for the evaluation of a movement
  attempt Was the movement correct?
• Error signal updates the recall schema

17
Dynamic System Theory

• Movement pattern is thought to emerge or
  self-organize as a function of the ever-changing
  constraints placed upon it

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Constraints

• Defined as the boundaries that limit the movement
  capabilities of an individual
• Three types
• Organismic structural or functional
• Body type, wt, ht
• Psychological, cognitive, emotional
• Environmentalwind, light, flat surface, grassy
• Task

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Task Constraints

• The goal of task a certain movement
• Rules that may limit the movement
• One must serve the tennis ball within an area on
  the baseline
• Implements or machines
• Using a walker, using weight machines, using a
  ball

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Attractor States

• Systems prefer states of stability
• When a change in constraints is imposed on a
  system, its stability is endangered
• Deep basins stable systems difficult to
  change
• Shallow basins less stable more susceptible
  to change

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Phase Shifts

• Changes in behavior are the result of a series of
  shifts
• Control parameters
• Variables that move the system into new attractor
  states gaining leg strength to perform a skill
  better
• Rate limiters
• Constraints that function to hinder or hold back
  the ability of a system to change Adult learner,
  fear

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So what happens when a skill performance needs to
change?

• Practice strategies need to create instability in
  a deep attractor basin
• As the skill moves through the phase shift, it
  will become a combination of the old and new ways
• At some point it will be neither the old or new
  and performance effectiveness is reduced
• Eventually through practice, a new attractor
  state is formed, and eventually a new deep basin

23
Key Point

• Movement patterns prefer state of stability
• New movements self-organize and emerge with phase
  shifts where attractors stabilize and destabilize
  as a function of the control parameters

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Practical Application

• Explain how orthotics function from a dynamic
  system perspective

25
Exit Slip

• How do the recall and recognition schema work
  together?
• How are phase shifts indicative of behavioral
  change?