Changes in Bilateral Phase Synchronization in Parkinsonian Tremor Related to Amplitude Difference

Abstract

Tremor, which is a manifestation of the Parkinson's disease, is rhythmic and involuntary oscillation in the frequency range from 3 to 8 Hz. Physiological mechanisms of parkinsonian tremor have not been clearly revealed even though there have been many related studies. In this study, we attempted to analyze bilateral phase synchronization between both hands in order to interpret parkinsonian tremor dynamics which can be helpful to speculate the mechanisms of parkinsonian tremor. Eighteen subjects with Parkinson's disease participated in this study. Tremor was measured for 30 seconds by three axis accelerometer placed over the middle finger with sampling frequency of 64Hz and 12 bit A/D converter while subjects were resting on a chair and relaxing both hands on their knees. Three kinds of synchronization indexes, and , were employed to assess the synchronization strength for tremor between both hands. As a result, when bilateral difference of tremor amplitude became larger than specific value, phase synchronization strength was significantly increased. Therefore, we may suppose that the dynamics of parkinsonian tremor have two modes of the non-phase synchronization and phase synchronization between both limbs.