Effects of the stimulus phase on the air-conducted ocular vestibular evoked myogenic potential in healthy subjects.

Abstract

The study aimed to examine the effect of the stimulus phase of air-conducted sound on ocular vestibular evoked myogenic potentials (oVEMPs). oVEMPs were recorded after air-conducted sounds (500Hz, 4ms duration), presented with initial condensation (positive), rarefaction (negative), and alternant polarities from 12 healthy subjects. Most responses showed a bifid n10 peak separated by ∼1.9ms. The most prominent sub-peak after condensation was shorter than the most prominent sub-peak after rarefaction; however, the first sub-peak was shorter after the rarefaction stimuli. When a third sub-peak appeared, it occurred before the most prominent sub-peak after condensation and after the most prominent sub-peak after rarefaction. The latency difference between this third sub-peak and the closest sub-peak was shorter than the difference among the others sub-peaks, in both cases; the oVEMPs after alternating stimuli was an amalgam of the responses to the different stimuli. The findings suggest that the negative to positive change of the stimulus was the main event responsible for the stimulation, and that when a third sub-peak appeared it was related to the initiation or the end of the stimulus. These findings suggested that the oVEMP response, obtained by air conducted sound, was secondary to stimulation of the same type of afferent vestibular unit, independent of the stimulus polarity.