Motor Control Theories

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Chapter 5

• Motor Control Theories

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Why do we need theories?

• Explanations
• Predictions
• Applications

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Motor control theories

• Explain
• Predictions
• Application

4
Essential features of motor theories

• Coordination
• Degrees of freedom
• Control

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Closed-loop control

• Feedback guided control

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Open-loop control

• Completely planned control

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Identify the primary control process
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Advantages and disadvantages

• Advantage of closed-loop
• Disadvantage of closed-loop
• Advantage of open-loop
• Disadvantage of open-loop

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Motor program theories

• Centrally stored
• Rule based
• What is a program?

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Schmidts Schema theory motor program

• Generalized motor program (GMP)
• Motor response schema
• Degrees of freedom problem

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Invariant features and parameters

• Invariant features
• Parameters
• Hitting a baseball
• Locomotion
• Writing your name

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Discrete actions and GMPs
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Locomotion stride analysis
Stance
Swing
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Rhythmic actions and GMPs
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Dynamic pattern theory Key concepts

• Self-organization
• Attractor
• Coordinative structure
• Order parameter

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Behavior without a detailed program
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Behavior without a detailed program
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Dynamic pattern theory key concepts

• Perception-action coupling

• Control parameter

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Dynamic patterns 11 timing (slow)
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Dynamic patterns 11 (fast)
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Dynamic patterns mn
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Dynamic patterns self-organization in human
motor skills

• What is an order parameter for human actions or
  motor skills?

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Dynamic patterns non-linear change in an action

• Movement frequency as a control parameter

A
B
D
A
D
D
1.5 Hz
1.75 Hz
2.0 Hz
2.5 Hz
Ab RH Ad
Ab LH Ad
Ab LH Ad
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Dynamic patterns compare in-phase and anti-phase

• Relative phase is an order parameter

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Dynamic patterns from muscle to limbs
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Dynamic patterns from cortex to limbs

• Brain patterns
• Neural energy
• Neural crosstalk

Left-H.
Right-H.
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Interpersonal coordination skills

• Schmidt et al. (1990)

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Interpersonal dynamics

• What happened when movement frequency was
  increased?

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Perceptual threshold

• Smooth pursuit eye movements

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Dynamic patterns locomotion

• How would the dynamical systems theory explain
  the gait transition?

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Chapter 6

• Touch, Proprioception and Vision

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Perception-action

• All actions require a transfer of perceptual
  information into motor commands
• Closed-loop control
• Open-loop control

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Tactile sensations

• Mechanoreceptors
• Role in action control (closer look 109)

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Proprioception limb and body position and
movement

• Muscle spindles
• Golgi-tendon organs (GTO)
• Joint receptors

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Deafferentation

• Surgical
• Temporary
• Neuropathy
• Tendon vibration

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Sensory neuropathy loss of proprioception

• Blouin et al. (1993)
• Independent variables
• Dependent variable

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Sensory neuropathy loss of tactile and
proprioception

• Bimanual coordination (Spencer et al. 2005)
• Draw two circles

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Sensory neuropathy loss of proprioception
Vision of

• Patients

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Vestibular system head and body position and
movement

• semi-circular canals

• otolith organs

• balance

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Vestibular and visual systems feedback control
and balance

• Task Maintain balance on a moving support
  surface - 12 cm
• Kinematics video cameras
• Platform speed (Hz)
• Feedback conditions

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Vestibular loss postural responses

• Buchanan and Horak (1999) Buchanan and Horak
  (2002)

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Platform speed postural responses

• Postural behavior

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Questions

• 1) How did the loss of vestibular information
  influence balance and posture?
• 2) How did platform velocity affect balance and
  posture?
• 3) What did visual information contribute to
  balance control?

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Visual Fields aligning vision (in) and motor
(out)
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Vision and motor control

• Visual field

• Central vision
• Peripheral vision

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Vision and motor control

• Vision-for-action (dorsal stream)
• Vision-for-perception (ventral stream)
• Two distinct neural pathways

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Vision and motor control

• Reaching and grasping
• Describe a cup
• Reach for a cup

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Vision and motor control

• Optical field
• Optical flow

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Contact with objectsstationary and
non-stationary

• Estimate contact
• Braking a car
• Time to contact with an object (tau)

STOP
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Sensation and perception

• Sensation - information pickup or selection
• Perception - interpretation of sensory
  information
• Motor theories

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Same information Different Perception!
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Chapter 7

• Performance and Motor Control Characteristics of
  Functional Skills

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Speed-accuracy skills

• What influences the accuracy of our movements?
• If you must be very accurate How does this
  impact your movement time?
• How does your CNS control the relationship
  between speed and accuracy?

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Speed-accuracy tradeoff Fitts Law

• 4 target sizes W
• 4 amplitudes D
• 16 pairings of D and W

• Independent variable
• Dependent variable

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Speed-accuracy tradeoff hypotheses

• Movement amplitude, D 16
• Target width, W 1

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Speed-accuracy tradeoffFitts original findings

• Fitts (1954)

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Fitts Law information as bits

• What did Fitts propose?
• Where does the speed-accuracy tradeoff come from?
• Can he quantify difficulty and load?

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Computing ID number of bits

• ID log2 (2D/W) bits
• 2u v
• 2ID 2D/W
• As ID increases, the load increases

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Examples of ID

• D 8 and W 1
• D 8 and W 2
• D 16 and W .5
• D 4 and W 1
• In class
• Big targets W 1.46, A 4
• Small targets W .05, A 4

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Fitts task
data
data
Movement time (MT) in this task is defined as
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Fitts Law Predicting MT

• MT a b(log2(2D/W)) a b(ID)
• Example

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Fitts data as bits of information

• Why do the conditions (D 2, W 1/4) and (D
  16, W 2) produce the same MT?

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Fitts Law open and closed-loop processing
A.
B.

• Condition A ID 3.
• Condition B ID 6

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Brain circuits and Fitts law

• Winstein, Grafton and Pohl (1997)
• High ID condition (6.2) discrete (closed-loop)
• Low ID condition (3.2) continuous (open-loop)

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Unilateral brain damage (stroke) and Fitts task

• Winstein and Pohl (1995)
• 3 D/W conditions
• Right or Left hemisphere

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Displacement and velocity

• Open-loop (planning) and closed-loop (feedback)
  control

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Hemispheric specialization

• Right hemisphere lesion High ID
• Left hemisphere lesion
• Conclusions

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Conclusions on Fitts Law

• Why is there a speed-accuracy trade-off?
• Why do MTs get longer as ID increases
• Real word examples

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Rhythms and control of gait

• Biomechanics of walking
• Slow walking pace
• Normal walking pace
• Neurophysiology of locomotion
• Locomotion 3-way interaction

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Perception-action coupling time to contact

• Lee, Lishman and Thompson (1982)

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Theoretical explanations of time-to-contact and
long-jump adjustments

• Motor programming versus Dynamic pattern
• How would the two theories explain the same
  event?
• Acceleration phase
• Adjustment phase

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Perception-action coupling Parkinsons disease

• Can hypo-kinesia be modified in Parkinsonian
  patients? Morris et al. (1994)
• What visual variable might provide information
  that can influence walking?
• Task
• Results

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Modification of Parkinsons gait

• Visual targets

• Targets
• Degeneration of basal ganglia in Parkinsons
  disease

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Vision and arm control

• Manual aiming

• Prehension
• Reaching and grasping
• Actions utilizing visual guidance of arm and hand
  motions

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Vision and catching ending flight

• Smyth Marriott (1982) vision and catching

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Vision and catching ending flight and experience

• Fischman Schneider (1985) experience and
  catching
• Always see your the hand (vision)
• Hand is covered (no vision)

grasp
Pos
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Chapter 11

• Defining and Assessing Learning

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Performance versus Learning

• Performance
• Learning

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Performance indicators of learning

• As a motor skill becomes
• Rate of change in performance

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Linear acceleration
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Negative acceleration
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Positive acceleration
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S-shaped
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Developing a new motor program

• Tracking task

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Learning a new coordination pattern

• Coordination task competition

flx
flx
flx
left arm
left arm
left arm
ext
ext
ext
flx
ext
flx
ext
flx
ext
right arm
right arm
right arm
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Learning a new coordination pattern

• What you can do influences what you want to do?

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Tests of learning

• Important to differentiate acquisition effects
  (practice) learning effects