ABSTRACT
A modern conceptual framework for vestibular function is that of a biological control
system. The use of control theory and techniques can have a major impact in vestibular
testing through monitoring of natural movements. The vestibulo-ocular reflex (VOR)
functions mainly to allow clear vision during walking by stabilizing the eye during
faster head movements. The Vestibular Autorotation Test (VAT™) tests the VOR at higher
frequencies (i.e, 2-6 Hz) encountered during natural, active movements. Horizontal
and vertical head movements are recorded for 18 sec. Spectral coherence Fourier analysis
in the VAT sorts head and eye movements into respective frequency components, and
computes VOR gain, phase, and asymmetry. A clinical example is used to illustrate
VAT gain and phase characteristics, and its effectiveness in monitoring vestibular
rehabilitation. Comparisons with traditional vestibular tests illustrate the advantages
of testing the vestibular system at higher frequencies with natural active head movements.
KEYWORDS
Vestibulo-ocular reflex - biological control - active head movements - Vestibular
Autorotation Test - dizziness