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Controlling Movement. Underlying Questions. What is being controlled? How is movement controlled? What beliefs exist to explain this control?. Degrees of Freedom. Number of ways independent components of a system can act Motor units Muscles Joints
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Underlying Questions • What is being controlled? • How is movement controlled? • What beliefs exist to explain this control?
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?
Coordination • The process by which an individual condenses the available degrees-of-freedom • Movement patterns constrained by characteristics of the environment
Control Mechanisms Closed-Loop commands control center effectors comparator feedback
Closed-Loop Control • Involves use of feedback and error detection & correction to maintain desired goal Type of skills (classification)? Examples? Driving a Car!
Control Mechanisms Open-Loop commands effectors control center
Open-Loop Control • Use of centrally determined, prestructured commands sent to effectors and run off without use of feedback Type of skills (classification)? Examples?
Open-Loop vs. Closed-Loop Control • What factors determine which control system is employed? Skill level Duration of movement
Control Explanations • Information Processing Input Perception Decision Making Execution Output Feedback
Information Processing Model • Movement planning & execution are responsibility of cortical command centers • Movements stored in form of Generalized Motor Program (GMP)
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
GMP • Accounts for performance of movements in absence of feedback • Movements in different contexts • Novel movements are possible HOW?
GMP & Parameters • Parameters - modifiable features of GMP • Variations in movement time • Variations in movement amplitude • Variations in limb & muscles used
Control Explanations • Dynamic Systems Action Perception
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