Ocular vestibular evoked myogenic potentials (oVEMPs) are a recently described clinical measure of the vestibulo-ocular reflex. Studies demonstrating differences in frequency tuning between air-conducted (AC) and bone-conducted (BC) oVEMPs suggest a separate vestibular (otolith) origin for each stimulus modality. In this study ten healthy subjects were stimulated with BC stimuli using a hand-held mini-shaker. Frequencies were tested in the range of 50 to1000 Hz using both a constant force and constant acceleration method. Subjects were stimulated at the mastoid process and the forehead. For constant force stimulation at both sites, maximum acceleration occurred around 100 Hz, in differing axes. Both forms of stimulation had low-frequency peaks of oVEMP amplitudes (constant force: mastoid - 80 to 150 Hz; forehead - 50 to 125 Hz; constant acceleration: mastoid - 100 to 200 Hz; forehead: 80 to 150 Hz), for both sites of application, despite differences in the magnitude and direction of evoked head acceleration. For mastoid stimulation ocular responses changed from out of phase to in phase for 400 Hz and above. Our results demonstrate that BC stimuli show tuning around 100 Hz independent of stimulus site that is not due to skull properties. The findings are consistent with an effect on a receptor with a resonance around 100 Hz, most likely the utricle.
- Ocular VEMP
- Copyright © 2011, Journal of Applied Physiology