Experimental Determination of a Portion of the Human Vestibular System Response Through Measurement of Eyeball Counterroll

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Abstract
This work was undertaken to obtain a description of a portion (the otolith organs) of the human vestibular system. The vestibular system is fairly inaccessible; thus, measurement by direct observation is difficult. Previous research has shown that eyeball counterroll is one external manifestation of the vestibular system response. In this work, therefore, an indirect measurement of the human vestibular system response was obtained through the measurement of eyeball counterroll. Human subjects were rotated about an axis through their line of sight at angular velocities varying from 0-20r/min. The right eye was photographed and the angle of eyeball counterroll was determined by an optical correlation process. A mathematical expression for input-output characteristics for rotation inputs was formulated using Fourier curve fitting techniques. This description indicates that subjects with normal vestibular function demonstrate an eyeball counterroll which is a function of angular velocity and position with respect to the vertical. Subjects with known vestibular defects demonstrate a small counterroll.