Temporal modulation transfer functions of amplitude-modulated cVEMPs in young adults

Communication Sciences and Disorders: Clinical Audiology
Advisors: Dr. Christopher Clinard, Dr. Andrew Thorne, and Dr. Erin Piker

The vestibular system is housed in the inner ear and is responsible for maintaining one’s balance and orientation in space. The present study tests this sensory structure in a novel manner in hopes of gaining a better understanding of typical, as well as pathological, findings within the vestibular system. Cervical vestibular evoked myogenic potentials (cVEMP) are recognized as a measure of the functional integrity of the saccule and the inferior vestibular nerve. cVEMPs can be recorded from the sternocleidomastoid muscle when the muscle is contracted, such as when the head is turned. Typically, transient tonebursts are used to elicit cVEMPs; in this study, we used bone-conducted amplitude-modulated (AM) 500 Hz tones to elicit AMcVEMPs. This novel approach allows the examination of phase-locked vestibular responses across a range of modulation frequencies. Currently, the AMcVEMP temporal modulation transfer function (TMTF) is not well defined. The upper frequency limit has not been established for amplitude or signal-to-noise ratio (SNR). While it has been shown that modulation frequencies close to 37 Hz elicit robust AMcVEMPs, the TMTF has not been examined with a wide range of modulation frequencies. This study works to further investigate the TMTF in AMcVEMPs to provide further information on the basic physiology of this response. The purposes of the present study were 1) to characterize the AMcVEMP TMTF in young, healthy individuals, and 2) to determine the upper frequency limit of the AMcVEMP TMTF. The hypotheses of the present study were that 1) AMcVEMP amplitude, SNR, phase coherence, and modulation gain will change with modulation frequency, and 2) responses will be present at modulation frequencies greater than 150 Hz.