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

Tasmania

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 a clock-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.

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

Zelaznik et al. (2002) 1. Tapping 2. Unimanual Continuous Circle Drawing 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) 800-ms MT 400-ms Movement 400-ms Pause 800-ms ITI

AIMS 1.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

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

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

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

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

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

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)

Sample Circle Drawing Trajectories Continuous Circle Drawing LH RH Intermittent Circle Drawing LH RH LHRH LH RH

Temporal Values ______________________________________________ Task MT (ms) SE CV(%) Slow Fast Slow Fast Slow Fast _______________________________________________________ Cont Circling Inter Circling Total Movement Pause * _______________________________________________________ *Continuous – Slow = 1000 ms, Fast = 588 ms Intermittent – Slow = 1400 ms, Fast = 988 ms

Intermittent Circling - Attention

Correlations _________________________________ Intermittent Circling ___________________________ MeasureTotal MovementPause ____________________________________________________ Continuous Circling Intermittent Circling Total Movement.56 Pause _____________________________________________________

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

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

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

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

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

REACTION TIME

Stability and Probe RT UniformityProbe reaction time

REACTION TIME MeanSE%age Pause Movement % (55) 64% (99)

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 movements incur greater central cost than continuous movements Conclusions

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

SW Wilderness