The amplitude-modulation-following response as an audiometric tool
Griffiths, Scott Keith
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https://hdl.handle.net/2142/20637
Description
Title
The amplitude-modulation-following response as an audiometric tool
Author(s)
Griffiths, Scott Keith
Issue Date
1990
Doctoral Committee Chair(s)
Chambers, Ron D.
Department of Study
Speech and Hearing Science
Discipline
Speech and Hearing Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Health Sciences, Audiology
Language
eng
Abstract
The amplitude-modulation-following response (AMFR) is a sinusoidal auditory-evoked potential recorded to continuous, sinusoidally amplitude-modulated tones. Kuwada, et al. (1986) defined the AMFR and argued its audiometric utility. The current study consisted of four experiments designed to demonstrate the utility of the AMFR. The experiments were: (1) demonstration of the cochlear site-specificity of the AMFR in high-pass and low-pass masking paradigms and comparison of behavioral and AMFR thresholds using spectral analysis; (2) valuation of the influence of sleep on the AMFR; (3) examination of the effects of modulation frequency on the AMFR; and (4) assessment of the effect of sensorineural hearing loss on the AMFR. Subjects in this study were six normal-hearing and three hearing-impaired adults.
The high-pass masking results demonstrated the AMFR to be associated with a narrow range of activation along the cochlea around the carrier frequency. Low-pass masking conditions yielded no decrease in AMFR amplitudes, indicating that the low modulation frequency AMFR does not depend on activation of apical fibers. Thresholds for the AMFR, defined in spectral terms, were correlated to behavioral estimates. A small reduction in AMFR amplitude was observed during sleep, although the effect was not consistent. Alternative modulation frequencies yielded an amplitude curve for the AMFR in which amplitude decreased from large values below approximately 75 Hz to smaller values above 100 Hz. This function showed no harmonic effects, i.e., harmonic sequences did not yield larger amplitudes. Although AMFR amplitude curves only generally reflected the curvature of the hearing loss in the hearing-impaired subjects, AMFR thresholds were consistent with the behaviorally-assessed values in all subjects. These results were discussed in terms of the audiometric utility of the AMFR and in terms of alternative analysis procedures.
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