Electrophysiological and Psychophysical Measures of Auditory Temporal Processing Public Deposited

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  • March 19, 2019
Creator
  • Mamo, Sara
    • Affiliation: School of Medicine, Department of Allied Health Sciences, Division of Speech and Hearing Sciences
Abstract
  • Older adults experience greater difficulty than younger adults understanding speech in noisy, complex backgrounds. This deficit remains even when the older adults have nearly normal hearing on standard audiometric testing. Independent of hearing loss, there is evidence of age-related declines in auditory temporal processing. These suprathreshold processing deficits have been implicated as contributing factors to reduced speech perception in noise. This project uses a combination of electrophysiology, psychophysics, and speech-in-noise measures to consider temporal processing in terms of sensory and perceptual coding of complex, periodic sounds. The use of combined methods is an important approach for parsing auditory and non-auditory factors underlying speech perception abilities in older adult listeners. The hypotheses are that (1) older adults exhibit reduced amplitudes for encoding sustained stimulus components on a speech-evoked auditory brainstem measure (sABR), (2) older adults have higher thresholds for the detection of a change in the periodicity of a complex tone, and (3) these measures show within-subject correlations such that individuals with robust sABR components demonstrate more sensitive perception of temporal periodicity cues. If the hypotheses are supported, these results will improve our understanding of auditory processing deficits underlying speech perception challenges for older adults. To test these hypotheses, two experiments were undertaken. In experiment 1, younger and older adults participated in a sABR measure, a harmonic mistuning task, and a masked speech perception task. These measures focused on temporal envelope encoding with the intention of relating the electrophysiological and psychophysical responses to an individual's ability to benefit from temporal modulations in background noise when listening to speech. In experiment 2, the younger and older adults were compared for their encoding of both temporal envelope and fine structure on a sABR measure. In addition, a model of neural temporal jitter was tested within a sABR paradigm with the goal of simulating in younger adults the response characteristics of the older adults. Specifically, the synthetic speech token used to elicit the sABR was submitted to a jitter algorithm that disrupted the periodicity cues of the stimulus. Taken together, results from these experiments support the notion of reduced neural synchrony for older adults with normal hearing. Future directions should focus on determining the temporal measures most predictive of speech perception abilities in noisy, complex backgrounds.
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  • In Copyright
Advisor
  • Jacks, Adam
  • Grose, John
  • Leibold, Lori J.
  • Buss, Emily
  • Fitzpatrick, Douglas
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2014
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  • Chapel Hill, NC
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