Tuning of the ocular vestibular evoked myogenic potential (oVEMP) to AC sound shows two separate peaks
The ocular vestibular evoked myogenic potential (oVEMP) is a relatively new method used to assess otolith-ocular pathways in humans. When elicited using air-conducted (AC) sound stimulation, the oVEMP is thought to reflect mostly saccular activation. However, it has been recently suggested that utricular afferents may also contribute to the AC evoked oVEMP. While previous frequency tuning studies of the AC evoked oVEMP report predominately high frequency sensitivity (>400 Hz), few have included the lower frequencies (<200 Hz) at which it has been proposed the utricle is most sensitive. In this study, ten normal subjects were stimulated with AC sound delivered unilaterally using headphones over frequencies from 50 to 1,200 Hz at a near constant A-weighted intensity of 120 dB peak sound pressure level. For AC stimulation, the oVEMP demonstrated maximum amplitudes around 600 Hz, with a second, smaller peak occurring around 100 Hz. The AC evoked oVEMP tuning has two peaks, a dominant one consistent with excitation of the saccule and a smaller one consistent with excitation of the utricle.