Dynamics of movement coordination and tremor during gait in Parkinson's disease

Abstract

Movement coordination, transition and stability aspects of gait in individuals with Parkinson's disease were investigated. Changes in movement coordination were evaluated by means of relative phase changes between upper and lower extremities and stability of patterns by means of the standard deviation of relative phase. Spectroscopic analysis of individual limb oscillators and of the relative phase between these oscillators was used to assess the contribution of lower and higher (e.g., tremor) frequency components on the coordination dynamics. Coordination changes in five patients and five age-matched controls were evaluated by means of accelerometry while movement velocity was manipulated as a control parameter on a motor-driven treadmill. Relative phase changes and stability features showed gradual changes in upper and lower extremity oscillations with walking velocity, a finding consistent with model predictions by Schöner et al. (1990) regarding gait changes in the quadrupedal walking mode. Parkinson's disease patients showed overall less adaptations in relative phase than the control group, especially those involving the upper extremities. Frequency analyses of relative phase also demonstrated that 1. (a) systematic scaling of walking velocity can affect the dominant frequency of Parkinsonian tremor, 2. (b) higher order frequency components in relative phase can play a functional, stabilizing role, and 3. (c) 1/ƒ scaling properties of the relative phase power spectrum can identify the higher degree of constraint on the coordination dynamics in Parkinson's disease.