CROSS-SPECTRAL ANALYSIS OF PHYSIOLOGICAL TREMOR AND MUSCLE-ACTIVITY -I - THEORY AND APPLICATION TO UNSYNCHRONIZED ELECTROMYOGRAM

We investigate the relationship between the extensor electromyogram (E MG) and tremor time series in physiological hand tremor by cross-spect ral analysis. Special attention is directed to the phase spectrum and the effects of observational noise. We calculate the theoretical phase spectrum for a second-order linear stochastic process and compare the results to measured tremor data recorded from subjects who did not sh ow a synchronized EMG activity in the corresponding extensor muscle. T he results show that physiological tremor is well described by the pro posed model and that the measured EMG represents a Newtonian force by which the muscle acts on the hand.