Frequency Tuning in the Tone Burst-Evoked Myogenic Potentials in Extraocular Muscles in Normal Human Subjects

Objective: In this cross-sectional study, we investigated the frequency tuning properties of sound-evoked vestibular myogenic potentials in extraocular muscles (OVEMPs) in normal human subjects. Methods: Acoustic tone bursts (130 dB pSPL, 10 ms plateau, 1 ms rise/fall) with nine frequencies from 125 to 4000 Hz were presented monoaurally to 12 normal subjects while they sat upright and maintained centre gaze. Using surface electrodes, the OVEMPs were recorded at four locations surrounding the contralateral eye (superior, inferior, nasal, and temporal) and were referenced to an electrode placed at the nape of the neck over C7. To measure the amplitudes of the OVEMP, signals from the electrodes were amplified and sampled at 10 kHz and were averaged over 250 repetitions. Results: We found that the OVEMPs recorded at the four sites exhibited similar well-defined frequency tuning with peak amplitude at approximate to 1000 Hz. Conclusion: Although several studies have examined the frequency tuning of the vestibular evoked myogenic potential measured from the sternocleidomastoid muscles (SVEMP), the reported results are quite variable as regards frequency, which produces peak amplitude. The well-defined OVEMP frequency tuning provides an alternative to the SVEMP for assessing vestibular function via acoustic stimulation. Further studies are needed to identify the extent to which each of the five vestibular end-organs is activated by sound and their contribution to the sound-evoked vestibular myogenic potentials.