Comparisons between the physiological, shivering, and parkinsonian tremors

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Abstract
We recently reported that sensory feedback contributes importantly to the amplitude and frequency of the shivering tremor. The present paper is concerned with comparisons between the rhythmlclty of shivering and that of physiologica tremor and parkinsonian tremor. Using an accelerometer to gauge the frequency-force characteristics of the tremors it was found that: like shivering, the amplitude of parkinsonain tremor was much reduced and frequency mildly increased by loading; physiological tremor, while affected similarly under light loading was more apt to display greater amplitude with higher loads; oscillatory periods were not set by time relationships around the proprioceptive routes from neuraxis to recording site. Variance in rates at different positions further indicated that none of the tremors were generated by an oscillatory drive distributed uniformly throughout the central nervous system motor outflow. The main significance of these findings is the attention they draw to the susceptibility of the three tremors to modification by local seg-mental mechanisms.