Controlling Movement

1
Controlling Movement
2
Underlying Questions

• What is being controlled?
• How is movement controlled?
• What beliefs exist to explain this control?

3
Degrees of Freedom

• Number of ways independent components
  of a system can act
• Motor units
• Muscles
• Joints
• How does the nervous system control the many
  muscles and joints involved in producing a given
  pattern? How does it solve this degrees-of-
  freedom problem?

4
Coordination

• The process by which an individual condenses the
  available degrees-of-freedom
• Movement patterns
  constrained by
  characteristics of the
  environment

5
Control Mechanisms

• Closed-Loop

commands
control center
effectors
comparator
feedback
6
Closed-Loop Control

• Involves use of feedback and error detection
  correction to maintain desired goal
• Type of skills (classification)?
• Examples?
• Driving a Car!

7
Control Mechanisms

• Open-Loop

commands
effectors
control center
8
Open-Loop Control

• Use of centrally determined, prestructured
  commands sent to effectors and run off without
  use of feedback
• Type of skills (classification)?
• Examples?

9
Open-Loop vs. Closed-Loop Control

• What factors determine which control system is
  employed?

Skill level
Duration of movement
10
Control Explanations

• Information Processing

Input
Perception
Decision Making
Execution
Output
Feedback
11
Information Processing Model

• Movement planning execution are responsibility
  of cortical command centers
• Movements stored in
  form of Generalized
  Motor Program (GMP)

12
Generalized Motor Program

• Abstract representation of stored pattern for
  class of action
• Prestructured set of movement commands
• Invariant features stored
• Particular muscles needed to produce action
• Order of muscle activation
• Relative timing sequencing of contractions
• Relative force of various muscle contractions
• Organizes many df into single unit for efficient
  and effective action

13
GMP

• Accounts for performance of movements in absence
  of feedback
• Movements in different
  contexts
• Novel movements are possible
• HOW?

14
GMP Parameters

• Parameters - modifiable features of GMP
• Variations in movement
  time
• Variations in movement
  amplitude
• Variations in limb muscles
  used

15
Control Explanations

• Dynamic Systems

Action
Perception
16
Dynamic Systems

• Planning of actions does not require elaborate
  cognitive processing
• Motor behavior emerges from interaction of
  multiple subsystems
• Actions shaped by intention of performer
  and constraints of environment