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

Abstract

Background 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. Purpose 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). Research Design Prospective, repeated-measures, within-subjects design. Study Sample Participants were 16 young, healthy adults (ages 21–38 years). Data Collection and Analysis 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. Results 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. Conclusion Analyses of AMcVEMPs are stable when the carrier frequency starting phase is altered and the phase of the temporal envelope is constant.

Temporal Modulation Transfer Functions of Amplitude-Modulated Cervical Vestibular-Evoked Myogenic Potentials in Young Adults

“…If vestibular hair cells on either side of the striola act has half-wave rectifiers, but for opposite polarities, then the otolith organ output as a whole would effectively act as a full-wave rectifier. In the present study, the largest response is expected at the modulation frequency, with an approximately exponential decline in amplitude at subsequent harmonics (Clinard et al 2020;Clinard et al 2021) because the response follows the temporal-envelope periodicity LAWLOR ET AL. / EAR & HEARING, VOL.…”

“…If vestibular hair cells on either side of the striola act has half-wave rectifiers, but for opposite polarities, then the otolith organ output as a whole would effectively act as a full-wave rectifier. In the present study, the largest response is expected at the modulation frequency, with an approximately exponential decline in amplitude at subsequent harmonics (Clinard et al 2020; Clinard et al 2021) because the response follows the temporal-envelope periodicity rather than the carrier frequency, or temporal fine structure. Stimuli in the present study alternated the polarity of the carrier frequency, but the phase of the temporal envelope was held constant; this resulted in maximal responses at the modulation frequency.…”

“…Tone duration was 1024 ms and sampling rate was 44.1 kHz. Stimuli were presented in alternating polarity (Clinard et al 2021).…”