1. Breaking It Down Is Better Haptic Decomposition of Complex Movements Aids in Robot- Assisted Motor Learning J. Klein, S. Spencer, & D. Reinkensmeyer IEEE Transactions on Neural Systems and Rehabilitation Engineering May 2012

2. Motivation – Klein et al. sports training rehab from neurologic injury – stroke – spinal-cord injury

3. Motivation – CHARM stroke rehab (Michele, Mike) needle-steering training (Ann) robot-assisted surgery (Ilana)

4. Background HAPTIC GUIDANCE of questionable effectiveness to date, been used almost exclusively to demonstrate entire movements “PART-WHOLE” TRANSFER sequential vs. continuous tasks effectiveness correlated with coordination requirements shoulder rotation elbow flexion/extension desired trajectory

5. Hypothesis “Decomposing” a movement into fewer-DOF components is more effective than training the movement as a whole. Moreover, the degree of effectiveness is dependent on the form of the decomposition.

6. Methods 4 DOFs 1.shoulder abduction/adduction 2.should flexion/extension 3.shoulder int./ext. rotation 4.elbow flexion/extension EULER

7. Methods 2 Motions 1.“main” (θ) ≈ tennis backhand 2.transfer (θ’) ≈ front crawl swim

8. Reflection… What if the task had been framed as a goal- directed movement? That is, what if subjects had been told: “pretend you are swinging a tennis racket”?

9. Methods Experimental Protocol 1.Baseline 2.Baseline Transfer 3.Training 4.Assessment 5.Assessment Transfer 6.Retention 7.Retention Transfer 4 Training Groups 1.“Whole” (control) 2.Euler 3.Anatomical 4.Visual

10. Reflection… Klein et al. randomized the presentation order of the joint components during Training. How necessary was this control? Is component presentation order an area for further study? rand{}

11. Methods Assessment “GLOBAL” lower score = better learning “LOCAL” * accounting for time delay d

12. Reflection… Why is it necessary to fit the shift parameter d? Shouldn’t d simply be the time between the assessment start signal and movement onset?...

13. Reflection… … Are we assuming that subjects are “playing catch up” with the virtual arm? What if, instead of being shown a virtual arm, subjects were given binary feedback (e.g., GREEN vs. RED) based on their current performance?

14. Results “MAIN” TRANSFER

15. Results no Baseline differences between decomposition groups all groups significantly improved with Training Anatomical decomposition exhibited greatest improvement during all assessments – Training – no significant difference compared to “Whole” – Short-Term – significant compared to all other groups – Long-Term – only (weakly) significant compared to Visual

16. Reflection… Why would there be greater learning at long- term retention (vs. short-term retention) for “Whole”, Euler, and Visual decompositions*? Given enough time, would all groups equalize? * Anatomical was approximately the same

17. Results “global” performance correlated with 1.“local” performance 2.proximity of training joint positions to those required by whole motion no improvement for transfer motion  haptic guidance training IS task specific

18. Discussion “Part-Whole” Learning counterintuitive success of Anatomical (vs. Visual) decomposition suggests that spatiotemporal summation mechanism operates in joint (vs. visual coordinates) * see (Kakei et al., 2001) NOT generalizable more spatial than temporal

19. Reflection… I am unconvinced by Klein et al.’s theory for why (anatomical) movement decomposition aids in learning a target motion more than practicing the motion itself. What other explanations can we propose? “One possibility is that the motor system has trouble determining where the problems lie in making, accurate, complex movements; breaking the movements down may allow better identification and then more focused practice on key problems.”

20. Discussion “Part-Whole” Learning counterintuitive success of Anatomical (vs. Visual) decomposition suggests that spatiotemporal summation mechanism operates in joint (vs. visual coordinates) * see (Kakei et al., 2001) NOT generalizable more spatial than temporal Robotic Movement Training opens the door for simpler robotic devices in rehab BUT, benefits of movement decomposition might only exist with haptic guidance

21. Reflection… What does this mean for stroke rehabilitation? Is there a “whole-part” mechanism that could help decouple patients’ abnormal muscle synergies? shoulder rotation elbow flexion/extension desired trajectory

22. “Breakthrough” or just another addition to the pool of inconclusive literature on haptic guidance?