ABSTRACT

Temporal characteristics of the input-output relations of the vestibulo-ocular reflex (VOR) were analyzed in terms of the magnitude and direction. Most VOR investigations using high-acceleration head rotations have recorded in one, two or three dimensions, but all the data have been analyzed in one dimension only, using VOR gain as the measurement criteria. These studies showed that unilateral vestibular deafferentation (uVD) leads to VOR gain deficits during yaw and pitch head rotations in humans. In normal subjects, the roll-torsional VOR response was weaker than the pitch-vertical and yaw-horizontal VOR responses. The results in uVD subjects show that the magnitudes of the VOR responses for roll, pitch and yaw impulses measured as Speed gains G are all significantly different from those observed in normal subjects. The presence of Speed gain deficits during both ipsilesional and contralesional head rotations indicates that both excitation and disfacilitation of the semicircular canals are essential for a normal magnitude of VOR response.