Interlimb coupling in a simple serial behavior: A task dynamic approach

Author(s): Saltzman, E. L., Turvey, M. T.

Journal/Book: Hum Movement Sci. 1998; 17: PO Box 211, 1000 AE Amsterdam, Netherlands. Elsevier Science BV. 393-433.

Abstract: Whereas rhythmic interlimb actions are characterized by an invariant spatio-temporal relation between the oscillating limbs, in serially coordinated movements the individual components' motions are discrete or intermittent, with little or no temporal overlap with other components' motions. An experimental and modeling framework is presented that systematically extends purely parallel rhythmic coordination towards serial rhythmic coordination. In two experiments subjects rhythmically moved a pendulum with the right hand in continuous fashion and performed a single, discrete cycle with a pendulum in the left hand every nth right-hand cycle. This pattern was rhythmic but not homogeneous in that it consisted of a globally repetitive sequence of unimanual and bimanual cycles. In Experiment 1, the two wrist-pendula's eigenfrequencies were identical, and the task involved a discrete cycle every fourth and fifth unit. The major results of the kinematic analyses were: (1) coupling during the bimanual cycle affected the amplitude, not the period of the continuous oscillations; (2) the discrete hand's movement showed characteristics of a damped oscillator displaying a ''ringing'' after its task-specified cycle; (3) the relative phase measures demonstrated immediate synchronization of the ''discrete'' event. Experiment 2 additionally manipulated the eigenfrequency difference delta between the two hands in the same task. The results from Experiment 1 were generalized with the additional findings: (4) While the amplitude magnification during the coupled cycle was indifferent to delta, the periods during the coupled cycle were affected by the discrete event: (5) relative phase at the coupled cycle was a function of delta in accordance with results in parallel interlimb coordination. These results were simulated by a three-layered task-dynamic network of coupled oscillators. This stratification allows for the assembly of a time-invariant dynamic regime that gives rise to seemingly discrete consequences on the level of the endeffector movements. .

Note: Article Sternad D, Penn State Univ, Dept Kinesiol, 266 Recreat Bldg, University Pk,PA 16802 USA

Keyword(s): serial order; dynamics; interlimb coordination; oscillator modeling; motor control; MUSCULO-SKELETAL SYSTEM; SIMPLE REACTION-TIME; RHYTHMIC COORDINATION; BIMANUAL COORDINATION; HUMAN LOCOMOTION; MOVEMENTS; MODEL; PHASE; PATTERNS; CONSTRAINTS

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