Jeff Summers, Sabrina Maeder, Cynthia Hiraga University of Tasmania, Hobart, Australia

1. COORDINATION DYNAMICS AND ATTENTIONAL COSTS OF CONTINUOUS AND DISCONTINUOUS BIMANUAL CIRCLE DRAWING MOVEMENTS Jeff Summers, Sabrina Maeder, Cynthia Hiraga University of Tasmania, Hobart, Australia

2. Tasmania

3. BACKGROUND • Different timing mechanisms have been proposed for continuous and discontinuous movements (Semjen, 2002; Zelaznik et al. 2002, Ivry et al. 2004) • Tasks that involve discontinuities (e.g., tapping) use aclock-like mechanism – event timing • Explicit temporal goals set for successive discrete events with an internal timing system controlling movement onsets. • Cerebellum important for event timing. • Temporal coupling between the hands arises through a common subcortical gating mechanism.

4. BACKGROUND • In tasks involving continuous movements (e.g., circle drawing) timing may be an emergentprocess without continuous control from an internal timing system–Emergent timing • Temporal consistency may reflect processes associated with trajectory formation and control. • Spatial and temporal coupling through communication across corpus callosum.

5. Zelaznik et al. (2002) 1. Tapping 800-ms ITI 2. Unimanual Continuous Circle Drawing 800-ms MT 3. Unimanual Intermittent Circle Drawing Higher correlations of temporal variability between tapping and intermittent circle drawing (r = 0.5) than between continuous and intermittent circling tasks (r = 0.27) 400-ms Movement 400-ms Pause

6. AIMS • To examine the coordination dynamics of discrete and continuous movements by comparing bimanual continuous (CC) and intermittent (IC) circle drawing Both continuous and intermittent circling tasks involve multijoint movements and task goal requires the production of coordinated bimanual periodic movements that conform to a specific trajectory.Intermittent circle drawing requires the insertion of a pause between each drawing cycle

7. AIMS Event timing in intermittent circling: a. Restricted to Pause Phase: Pause–event timing+Movement–emergent timing b. Hierarchical timer organisation: Highest Level –time between movement onsets Subordinate timer – pause interval

8. AIMS • To compare theattentional demandsof discrete and continuous bimanual movements • To examine the relationship between coordinationpattern stability and attentional demands in discrete and continuous movements • Central cost and pattern stability covary –(Temprado et al. 1999, 2001, Zanone et al. 2001)

9. TASKS 1.Continuousbimanual circle drawing Movement Time Slow: 1000 ms (1 Hz) Fast: 588 ms (1.7 Hz) Pause: 400 ms (IC) SymmetricalAsymmetrical 2. Intermittent bimanual circle drawing Symmetrical Asymmetrical

10. DUAL TASK PARADIGM Bimanual Circle Drawing + Probe RT Vocal RT Task

11. METHODS • Participants: 15individuals right handers • Coordination Tasks: Continuous (CC) - Intermittent (IC) Circle Drawing Trial = 30-s continuation • Probe RT Task 6-8tones (1400 Hz) per trial, ISI 500-1500 ms RT task response – vocal • Conditions Single-task:CC, IC, Probe RT Dual-task:CC + probe RT, IC + probe RT Prioritise coordination

12. DESIGN • 2 X 2 X 2 X 2 Repeated Measures • Task – Continuous, Intermittent Circle Drawing • Attention – Single-task, dual-task • Coordination mode – Symmetrical, Asymmetrical • (In-phase) (Anti-phase) • Frequency – Slow (I Hz), Fast (1.7 Hz)

13. Sample Circle Drawing Trajectories Continuous Circle Drawing LH RH LH RH Intermittent Circle Drawing LH RH LH RH

14. Temporal Values ______________________________________________ Task MT (ms) SE CV(%) Slow Fast Slow Fast Slow Fast _______________________________________________________ Cont Circling 989 592 10.98 5.87 4.30 3.84 Inter Circling Total1410 99816.54 9.95 4.54 3.86 Movement 965 689 12.58 7.89 5.05 4.43 Pause 445 309*13.92 9.31 12.12 11.67 _______________________________________________________ *Continuous – Slow = 1000 ms, Fast = 588 ms Intermittent – Slow = 1400 ms, Fast = 988 ms

15. Intermittent Circling - Attention

16. Correlations _________________________________ Intermittent Circling ___________________________ Measure Total Movement Pause ____________________________________________________ Continuous Circling - .02 - .10 .22 Intermittent Circling Total.81.64 Movement.56 Pause _____________________________________________________

17. Coordination Dynamics Measures Control parameter:e.g., frequency Order parameters:Collective level Component level (between hands)(within hands) Temporal (Circling Frequency, CV Freq) Spatial (Aspect Ratio: 0-1, Spatial Error) Phase lag (Relative tangential angle, RTA) Variability/Stability (Uniformity: 0-1)

18. Coordination Dynamics 1. Temporal Measures – AE RTA (Accuracy) Task x Frequency x Coordination Mode

19. Coordination Dynamics 1. Temporal Measures – Uniformity (Stability) Task x Frequency x Coordination Mode

20. Coordination Dynamics 2. Spatial Measures – Aspect Ratio(Circularity) Task x Frequency x Hand

21. Coordination Dynamics 2. Spatial Measures – Spatial Error(Variability) Task x Frequency

22. REACTION TIME

23. Stability and Probe RT Uniformity Probe reaction time

24. REACTION TIME

25. Conclusions • Different control processes involved in bimanual continuous and discontinuous movements • Discontinuous movements involve a hierarchical temporal representation with the time between successive movement onsets represented at the highest level • Continuous movements involve some form of emergent timing process • Discontinuous movementsincur greater central cost than continuous movements

26. Conclusions • Continuous and discontinuous bimanual circling movements exhibit different coordination dynamics at high movement rates • Both tasks showed a dissociation between stability and probe RT

28. SW Wilderness