Graduation Year

2014

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Communication Sciences & Disorders

Major Professor

Nathaniel D. Maxfield, Ph.D.

Co-Major Professor

Theresa H. Chisolm, Ph.D.

Committee Member

Rachel A. McArdle, Ph.D.

Committee Member

Jennifer J. Lister, Ph.D.

Keywords

age-related hearing loss, aging, event-related potentials, neurophysiology, presbycusis, speech perception

Abstract

Word recognition is based on the complex interplay of bottom up processing of acoustic input and corresponding top-down processing based on linguistic redundancies (i.e., contextual cues). Friedrich and Kotz (2007) investigated the timeline of integrating top-down and bottom-up processes among young adults with normal hearing using sentences presented in quiet. As a follow-up study, also with young adults with normal hearing (Experiment 1 of this dissertation), we used sentences embedded in multi-talker background noise and found similar results to Friedrich and Kotz (2007); but, with the use of principal component analysis (PCA) unveiled additional effects of phonological and semantic integration of spoken sentences presented in background noise. These past studies provide evidence of the time course of bottom-up and top-down mechanisms among young adult listeners in quiet and in noise; however, it is unknown if a similar pattern would be present among older adult listeners, which was the primary goal of the dissertation.

In Experiment 2, we aimed to elucidate the time-course, and behavioral and neural correlates of word recognition primed by speech-in-noise in older adults with near normal hearing (i.e., thresholds ≤ 25 dB-HL through 3000 Hz and minimal high frequency hearing loss). Older adults often report difficulty understanding speech in the presence of background noise. Degradation in peripheral and central auditory processing along with age-related cognitive decline has been hypothesized as reasons why older adults struggle in the presence of noise.

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