Quantifying the importance of high frequency components on the amplitude of physiological tremor.

The objective of this study was to determine the importance of every frequency component on total physiological tremor (PT) amplitude. We suspect that since high frequencies of PT are of lower amplitude in displacement, removing them will have little to no impact on PT amplitude. PT of the index finger was measured with a laser displacement sensor while the finger was held horizontally. Amplitude of tremor was calculated in displacement, velocity and acceleration. PT amplitude was also calculated within five frequency bands. Although displacement amplitude of oscillations within the 7.5-12.5 and 16.5-30 Hz frequency bands represent 24 and 10% of total PT oscillation amplitude, respectively, their removal reduced PT amplitude by less than 3%. Conversely, the removal of the oscillations within 1-3.5 Hz band from the PT signal reduced the amplitude of the original PT signal by 56% in displacement. This suggests that when a task to be studied involves the measurement of a reduction in tremor, focus should be on the oscillations in the 1-3.5 Hz band.