Chapter 15

1. Chapter 15 Basic concepts of motor control: Cognitive science perspectives

2. Cognitive science perspectives • Objective from syllabus • To understand how models of motor control can be used to explain how we move • The general notion is that the brain & CNS is rather too complex to fully understand at this time, so we need a level of analysis once removed

3. Using Models to Study Motor Control • The role of models in scientific study • Key properties to be explained by models of control • Degrees of freedom • Motor equivalence • Serial order • Perceptual-motor integration • Skill acquisition (ch. 17)

4. Information-Processing Models of Motor Control • The human motor system as computer-like • Hardware (brain, receptors, effectors) and software (computational capabilities of these) • Processing stages • See next 5 slides for examples (a model, followed by some movements that it might help explain)

5. Executive (conscious) Conscious intentions Executive (unconscious) Sets up the intended movement, with reference to current body state and environmental cues Central Pattern Generator Signal diversifies, with detail added at this level including necessary communication between muscles systems Feedback Loops Collections of motor units innervated, leading to contractions of various strengths Movement Environment Body movement affects environmental goals, and always changes our orientation with respect to the environment 1. A model Note many levels of control

6. Executive (conscious) So it’s fast, but doesn’t do much in terms of coordination Conscious intentions Executive (unconscious) Sets up the intended movement, with reference to current body state and environmental cues Central Pattern Generator Signal diversifies, with detail added at this level including necessary communication between muscles systems Feedback Loops Collections of motor units innervated, leading to contractions of various strengths Movement Environment Body movement affects environmental goals, and always changes our orientation with respect to the environment 2. A knee-jerk (stretch, myotatic, monosynaptic) reflex

7. Executive (conscious) Fast, due to lack of conscious mediation, and complex Conscious intentions Executive (unconscious) Sets up the intended movement, with reference to current body state and environmental cues Central Pattern Generator Signal diversifies, with detail added at this level including necessary communication between muscles systems Feedback Loops Collections of motor units innervated, leading to contractions of various strengths Movement Environment Body movement affects environmental goals, and always changes our orientation with respect to the environment 3. Balance (swinging room and normal)

8. Executive (conscious) Conscious deliberation makes performance jerky, stiff, awkward Conscious intentions Executive (unconscious) Sets up the intended movement, with reference to current body state and environmental cues Central Pattern Generator Signal diversifies, with detail added at this level including necessary communication between muscles systems Feedback Loops Collections of motor units innervated, leading to contractions of various strengths Movement Environment Body movement affects environmental goals, and always changes our orientation with respect to the environment 4. Poorly learned skill

9. Used just to get things started – will perhaps monitor for errors, but that’s perhaps not a good thing (self-talk) Executive (conscious) Lengthy practice “automates” performance – think of tying your shoelaces as an example Conscious intentions Executive (unconscious) Sets up the intended movement, with reference to current body state and environmental cues Central Pattern Generator Signal diversifies, with detail added at this level including necessary communication between muscles systems Feedback Loops Collections of motor units innervated, leading to contractions of various strengths Movement Environment Body movement affects environmental goals, and always changes our orientation with respect to the environment 5. Expertly learned skill

10. An Alternative Model of Motor Control • Problems with information processing accounts • Homunculi - Infinite regress (why do we walk the way we do?) • Context-conditioned variability • anatomical (muscles used to produce a given movement change with regard to current body ‘context’) • mechanical (action of a fixed degree of contraction of a muscle changes with respect to current body position) • Distributed, not central control

11. An Alternative Model of Motor Control • A group of related theories • Complex systems theory • Dynamic pattern perspective & synergetics • Ecological psychology • All have in common the tendency to ask why rather than how • The study of relationships among things, rather than the things themselves • Leads to the study of...

12. Dynamic Pattern Theory • Shaping movement via: • Constraints... • Things which limit our range of movements – thus “shaping” them • ...and affordances • Things which permit (or even suggest) certain methods of movement or interaction with an object

13. Individual Capabilities Environmental Constraints Task Demands Dynamic Pattern Theory From Newell (1986) Flexibility Cognition Strength/power Motor abilities Cardiovascular Sensory loss Speed/accuracy requirements Surface type moving seated Lighting standing Visual flow Environmental stability Number of tasks 3 categories of constraint (+ examples)

14. Dynamic Pattern Theory From Schmidt & Fitzpatrick (1993) Coordination dynamics Dynamics of CNS(neural level) Dynamics of action system (effector level) Dynamics of environment (environmental level) Connectionism Action system theory Laws of perceiving and acting (ecological psychology) Processes in coordination dynamics

15. Dynamic Pattern Theory • Constraints and affordances lead to pattern formation • Remember, this is a theory about shaping of movement • Why do we walk the way we do?

16. Dynamic Pattern Theory • An example of emergent patterns from motor development • Stepping/Walking • 0-2 months • Stepping a stable behavior • 3-4 months • Stepping disappears • Why? Where might you look if you believed in constraints and affordances? • How might you examine this?

17. Dynamic Pattern Theory • An example of emergent patterns from motor development 1 month 3 months How might you regain it? And how else might you lose it? What causes this loss of stability?

18. Dynamic Pattern Theory See anything that changes? 3 months New born

19. Dynamic Pattern Theory • An example of emergent patterns from motor development 1 month 3 months How might you regain it? And how else might you lose it? What causes this loss of stability?

20. Dynamic Pattern Theory • In complex systems terms, there are several aspects to this relationship: • Self-organization • Attractor • Order parameter • Control Parameter • Stability • Energy efficiency • Critical fluctuation • Critical slowing down • Hysteresis

21. An example from adult movement In-phase: Faster and faster… Kelso & Scholtz, 1985

22. An example from adult movement In-phase: Faster and faster… Kelso & Scholtz, 1985 Kelso & Scholtz, 1985

23. An example from adult movement Anti-phase: Faster and faster… Kelso & Scholtz, 1985 Kelso & Scholtz, 1985

24. An example from adult movement Anti-phase: Faster and faster… Kelso & Scholtz, 1985 Kelso & Scholtz, 1985

25. Coordination Stability Difference between jt. Angles Variation in jt. Angles (arbitrary units) An example from adult movement • Stability and attractors • The in-phase and out-of-phase states in the Kelso example are attractor states for the movement • Perturbing the movement when it is in a stable attractor region will result in a quick return to stability (in-phase)

26. Coordination Stability Difference between jt. Angles Variation in jt. Angles (arbitrary units) An example from adult movement • Stability and attractors • Perturbing the movement when it is close to a region of instability will result in either a longer period of instability followed by a resumption of the original state, or a new attractor state • When close to a period of transition, the movement will exhibit critical fluctuations • the movement will be more ‘wobbly,’ less stable

27. Aspects of dynamic systems Listen to this first! Then proceed with the others, going from 1 to 5 Hysteresis in gait 1 2 3 5 4

28. Aspects of dynamic systems Hysteresis in gait Run The difference in the speed (at which the person is running/walking) when the transition is made from walking to running, compared to when the switch is made from running to walking, signifies the presence of hysteresis – further definition in audio Order parameters Walk Speed (control parameter)

29. Aspects of dynamic systems • As it turns out, much the same relationship exists in many other systems: • Other examples of human coordination • Human cortical activity • Cardiac rhythms • Water flowing from a tap • Water being heated • Horses (& other quadrupeds) changing gait • Stock market, weather patterns, emotional fluctuations, etc.