Issues in Motor Control

1. Issues in Motor Control • Degrees of Freedom Problem • Perceptual-Motor Integration Problem • Serial Order and Timing Problem • Learning Problem (Rosenbaum, 2002)

2. Earlier Ideas Used Response Chaining: Closed (feedback)-Loop Control: • No, because • delays too long between movements • disrupting feedback does not necessarily impeded movement • Systematic mistakes in speech, typing, etc “He hissed all my mystery lessons” rather than “he missed all my history lessons”

3. Closed-Loop Control: Still Occurs • Can you think of an example? • Muscle spindle (20-30 ms) • Long-loop reflexes

4. Open-(feedforward) Loop Control • Anticipatory Control • Predictive Control • Prospective Control

5. Closed-Loop Control: Still Occurs http://www2.fhs.usyd.edu.au/ess/odwyer/Human%20Motor%20Learning%20and%20Control/Lectures/Week%206/Using_Information_FF_vs_FB_Control.pdf

6. Need for Closed and Open-Loop Systems http://www2.fhs.usyd.edu.au/ess/odwyer/Human%20Motor%20Learning%20and%20Control/Lectures/Week%206/Using_Information_FF_vs_FB_Control.pdf

7. What must be specified in advance for open-loop control to be accomplished? • Willingham (1999) • Donders (1868)

8. Strategic Allocentric Conscious P-M Integration Egocentric Un/Conscious Sequencing Egocentric Un/Conscious Dynamic Egocentric Unconscious

9. Information Processing

10. Solving motor control problems using Open-Loop Control: Plans or Programs • Evidence for planning movements in advance • Reaction Time approach RT is larger as task is more complex – Presumably this occurs because more demanding mental operations http://www2.fhs.usyd.edu.au/ess/odwyer/Human%20Motor%20Learning%20and%20Control/Lectures/Week%206/Using_Information_FF_vs_FB_Control.pdf

12. RT: Input-?-Output Movement Initiation GO Response Programming = Reaction Time

13. Perceptual-Motor Integration Sequencing or Serial Order

14. Parallel Processing Cascade Processing

15. Influences on RT RT is a volatile measure which is sensitive to many factors: • stimulus factors: • modality of presentation (visual, auditory, tactile, kinaesthetic) • intensity (loudness, brightness) • temporal predictability • number of response choices • stimulus-response compatibility • response complexity SRT CRT SRT

16. stimulus factors impacting SRT: • modality of presentation (visual, auditory, tactile, kinaesthetic) • intensity (loudness, brightness) • temporal predictability RT (ms) -- ++ Signal Intensity

17. Event Uncertainty and CRT • Number of response choices • Probability Effects • Precues • Sequential Effects

18. Hick’s Law CRT = a + b (log2 N) # Decisions CRT = SRT + DT (# Decision)

19. Precues What is being precued? Where is the impact? CRT = SRT + DT (# Decision)

20. Reducing Event Uncertainty: Probability Effects

21. Decision Time CRT = SRT + DT (# Decision) Stimulus-Response Compatibility • Degree of correspondence between the stimulus array and the response

25. CRT = SRT + DT (# Decision)

27. Perceptual-Motor Integration

29. Response Programming: What movement parameters must be planned?

30. Henry and Roger (1960) MT (ms) 0 95 465 208 Keep in mind that the RT for the finger lift is being measured here not MT: What movement parameter(s) were responsible for increase in RT

31. Using Henry & Rogers data: What are the key movement parameters that need to be planned? • Movement Duration • Number of Elements (sequence length effects) • Changes in Direction • Force/velocity requirements • Directions requirements

32. INT Complexity 150 ms 450 ms Simple SEQ Complexity 150-450-450-150 450-150-150-450 Complex Simple Complex Mono vs Multi-syllabic /ba/

33. Start Fixation Point Stimulus Display Study Time Ready ? Yes 100 % 15 % 0 % ‘ ’ GO Signal Reaction Time Speech Duration Analyze Interval Yes Error ? No Model Replay Rectified & Waveform Filtered End Self-select paradigm and speech Duration of programmed unit Number of programmed units

34. Defining complexity of the utterance INT Complexity CV ta CC(C)V stra Simple SEQ Complexity CV repeat ta-ta-ta-ta CC(C)V repeat stra-stra-stra-stra CC(C)V change ta-stra-ru-ta Complex Simple Complex

35. Apraxia of Speech (AOS): Is it a planning or programming problem? • Motor Planning • Van der Merwe (1997) • Motor Programming • Levelt (1989) • phonetic encoding leading to “phonetic plan” • Van Lieshout et al., (1996) • motor plan assembly and muscle command preparation

36. Closed vs. Open Loop Plans or Motor Programs Quantifying the plan: Reaction Time The plan (or RT) involves: Perception-Response Selection-Programming Verifying this model by finding factors impacting Perception-Response Selection-Programming (c)Rt = SRT + DT(# of Decisions)

37. (C)RT = SRT + DT(# of Decisions) Movement Duration Number of Elements (sequence length effects) Changes in Direction Force/velocity requirements Directions requirements • Modality of presentation • intensity (loudness, brightness) • temporal predictability Perceptual Process Motor Programming • Compatibility of S and R • Practice • Number of Alternative • Precues • Sequential dependencies Decision Making (response selection)