Effects of Tonic Muscle Activation on Amplitude-Modulated Cervical Vestibular Evoked Myogenic Potentials (AMcVEMPs) in Y
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JARO (2020) DOI: 10.1007/s10162-020-00766-z D 2020 Association for Research in Otolaryngology
Research Article
Journal of the Association for Research in Otolaryngology
Effects of Tonic Muscle Activation on Amplitude-Modulated Cervical Vestibular Evoked Myogenic Potentials (AMcVEMPs) in Young Females: Preliminary Findings CHRISTOPHER G. CLINARD,1
ANDREW P. THORNE,1
AND
ERIN G. PIKER1
1
Department of Communication Sciences and Disorders, James Madison University, 235 Martin Luther King Jr. Way, MSC 4304, Harrisonburg, VA 22807, USA Received: 14 December 2019; Accepted: 24 July 2020
ABSTRACT Cervical vestibular evoked myogenic potentials (cVEMPs) are usually elicited by transient tonebursts, but when elicited by amplitude-modulated (AM) tones, they can provide new information about cVEMPs. Previous reports of cVEMPs elicited by AM tones, or AMcVEMPs, have not systematically examined the effects of tonic EMG activation on their response properties. Fourteen young, healthy female adults (ages 20–24) with clinically normal audiograms participated in this study. AMcVEMPs were elicited with bone-conducted 500 Hz tones amplitude modulated at a rate of 37 Hz and recorded for five different EMG targets ranging from 0 to 90 μV. Amplitude increased linearly as tonic EMG activation increased. Signal-to-noise ratio (SNR) was minimal at 0 μV, but robust and with equivalent values from 30 to 90 μV; phase coherence and EMG-corrected amplitude had findings similar to SNR across EMG target levels. Interaural asymmetry ratios for SNR and phase coherence were substantially lower than those for raw or corrected amplitude. AMcVEMP amplitude scaled with tonic EMG activation similar to transient cVEMPs. Signal-to-noise ratio, phase coherence, and EMG-corrected amplitude plateaued across a range of EMG values, suggesting that these properties of the response reach their maximum values at relatively low Portions of these data were presented at the 2019 American Auditory Society Meeting. Correspondence to: Christopher G. Clinard & Department of Communication Sciences and Disorders & James Madison University & 235 Martin Luther King Jr. Way, MSC 4304, Harrisonburg, VA 22807, USA. email: [email protected]
levels of EMG activation and that higher levels of EMG activation are not necessary to record robust AMcVEMPs. Keywords: cVEMP, VEMP, otolith, steady statePortions of these data were presented at the 2019 American Auditory Society Meeting.
INTRODUCTION Otolith organs respond to linear acceleration of the head and gravity. They can also be excited by acoustic or vibratory stimulation (for a review, see Curthoys 2010). When the resulting response is recorded over the sternocleidomastoid muscle it is referred to as the cervical vestibular evoked myogenic potential (cVEMP) and reflects the integrity of the saccule and vestibulocollic reflex pathway (Colebatch and Halmagyi 1992). Traditional cVEMPs reflect inhibitory onset responses; are typically elicited by brief, transient stimuli; and consist of positive and negative peaks occurring a
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