Effects of Stimulus Polarity on Amplitude-Modulated Cervical Vestibular-Evoked Myogenic Potentials.

Abstract

Traditional approaches to cervical vestibular-evoked myogenic potentials use a transient stimulus to elicit an onset response. However, alternate approaches with long duration stimuli may allow the development of new methodologies to better understand basic function of the vestibular system, as well as potentially developing new clinical applications. The objective of this study was to examine the effects of stimulus polarity on response properties of amplitude-modulated cervical vestibular-evoked myogenic potentials (AMcVEMPs). Prospective, repeated-measures, within-subjects design. Participants were 16 young, healthy adults (ages 21-38 years). Amplitude-modulated tones, with carrier frequency of 500 Hz and modulation frequency of 37 Hz, were used to elicit AMcVEMPs. Responses were analyzed in three different stimulus polarity conditions: condensation, rarefaction, and alternating. The resulting data were analyzed for differences across polarity conditions. AMcVEMP amplitudes, both raw and corrected for tonic muscle activation, were equivalent across the different stimulus phase conditions. In addition, response signal-to-noise ratio and phase coherence were equivalent across the different phases of the stimulus. Analyses of AMcVEMPs are stable when the carrier frequency starting phase is altered and the phase of the temporal envelope is constant.