Frequency analysis of human involuntary eye movement.

Abstract

A discussion is given of considerations involved in forming a frequency spectrum of a signal such as human fixation eye movements, in which an impulsive signal (saccadic movements) and a noise-like signal (tremor movements) are present together. A method is outlined which enables the spectrum of each component to be determined. Results are presented of human eye movement frequency spectra and it is shown that the tremor movements alone are adequate to prevent the fading of vision under conditions of retinal image stabilisation. An interpretation of the observed frequency spectra is given in terms of a model, which assumes that the dynamics of the eye muscle system are linear and that the active state input producing tremor has a flat frequency spectrum. From this it is deduced that the eye behaves as an overdamped second order system with time constants of 0.002 and 0.02 seconds. The active state input involved in production of an involuntary saccade is shown to consist of an impulse function with exponential rise and decay.