Title

DYNAMIC MODELING OF RHYTHMIC LIMB MOVEMENTS: CONVERGING ON A DESCRIPTION OF THE COMPONENT OSCILLATORS

Date of Completion

January 1986

Keywords

Psychology, Experimental

Degree

Ph.D.

Abstract

One way to consider rhythmic movements (e.g., locomotion) is in terms of the dynamical properties of limit cycle oscillators. In this study, the dynamical properties of rhythmic finger movements were examined using perturbation and other techniques. In the comfort mode, it was found that: (1) movement frequency, amplitude, and peak velocity were stable under perturbation; (2) the dimensionality of the movement trajectories was approximately equal to that of mathematical limit cycles; (3) inferring from the significant phase shifts observed, the underlying dynamic is probably not that of a nonautonomous linear oscillator; and (4) the number of fundamental dynamical coordinates is greater than two, the minimum number necessary to describe periodic processes. In metronome-paced conditions, (1) phase response varied systematically with frequency of movement, from simple phase shift (Type 1) to more complex phase resetting (Type 0) behavior; (2) the strength of a postulated nonlinearity was a function of movement frequency as predicted by earlier modeling attempts; (3) and movement amplitude was not as stable as in the preferred case.^ Other results, including spectral analyses, are discussed in terms of particular dynamical regimes having similar properties. It is argued that simple two-dimensional dynamics cannot reproduce all of the important features displayed by the data, and an alternative framework of higher-dimensional dynamical equations is proposed. ^