Date of Award

Spring 2014

Document Type

Dissertation

Degree Name

Doctor of Audiology (AuD)

Department

Department of Communication Sciences and Disorders

Advisor(s)

Christopher G. Clinard

Brenda M. Ryals

Lincoln C. Gray

Abstract

Understanding a speech signal is reliant on the ability of the auditory system to accurately encode rapidly changing spectral and temporal cues over time. Evidence from behavioral studies in humans suggests that relatively poor temporal fine structure (TFS) encoding ability is correlated with poorer performance on speech understanding tasks in quiet and in noise. Electroencephalography, including measurement of the frequency-following response, has been used to assess the human central auditory nervous system’s ability to encode temporal patterns in steady-state and dynamic tonal stimuli and short syllables. To date, the FFR has been used to investigate the accuracy of phase-locked auditory encoding of various stimuli, however, no study has demonstrated an FFR evoked by dynamic TFS contained in the modulating frequency content of a carrier tone. Furthermore, the relationship between a physiological representation of TFS encoding and either behavioral perception or speech-in-noise understanding has not been studied. The present study investigated the feasibility of eliciting FFRs in young, normal-hearing listeners using frequency-modulated (FM) tones, which contain TFS. Brainstem responses were compared to the behavioral detection of frequency modulation as well as speech-in-noise understanding. FFRs in response to FM tones were obtained from all listeners, indicating a reliable measurement of TFS encoding within the brainstem. FFRs were more accurate at lower carrier frequencies and at shallower FM depths. FM detection ability was consistent with previously reported findings in normal-hearing listeners. In the present study, however, FFR accuracy was not predictive of behavioral performance. Additionally, FFR accuracy was not predictive of speech-in-noise understanding. Further investigation of brainstem encoding of TFS may reveal a stronger brain-behavior relationship across an age continuum.

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.