Abstract.
Most studies of movement coordination deal with temporal patterns of synchronization between components, often without regard to the actual amplitudes the components make. When such a system is required to produce a composite action that is spatially constrained, coordination persists, but its stability is modulated by spatial requirements effected, we hypothesize, through the component amplitudes. As shown experimentally in part I, when a redundant three-joint system (wrist, elbow, and shoulder) is required to trace a specified arc in space, the joint angles may be frequency- and phased-locked even as the curvature of the trajectory is manipulated. Transitions between joint coordination patterns occur at a critical curvature, accompanied by a significant reduction in wrist amplitude. Such amplitude reduction is viewed as destabilizing the existing coordinative pattern under current task constraints, thereby forcing the joints into a more stable phase relationship. This paper presents a theoretical analysis of these multijoint patterns and proposes an amplitude mechanism for the transition process. Our model uses three linearly coupled, non-linear oscillators for the joint angles and reproduces both the observed interjoint coordination and component amplitude effects as well as the resulting trajectories of the end effector.
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Received: 2 February 1996/Accepted in revised form: 13 December 1996
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de Guzman, G., Kelso, J. & Buchanan, J. Self-organization of trajectory formation . Biol Cybern 76, 275–284 (1997). https://doi.org/10.1007/s004220050339
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DOI: https://doi.org/10.1007/s004220050339