Graduation Year


Document Type




Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Communication Sciences and Disorders

Major Professor

David A. Eddins, Ph.D., CCC-A

Co-Major Professor

Ann C. Eddins, Ph.D., M.B.A., CCC-A

Committee Member

Jungmee Lee, Ph.D.

Committee Member

Brent Small, Ph.D.


central plasticity, homeostatic plasticity, presbycusis, sound generators


The primary goals of this dissertation were to 1) identify markers of central gain in the auditory system following short-term acoustic attenuation via earplugging and acoustic enhancement via sound generators, and 2) determine if acoustic enhancement is effective in modulating central gain in older adults with age-related hearing loss, and if so, to what extent. Additionally, a further goal of this dissertation was to explore the possibility that central gain is related hearing aid acclimatization. The results described in Chapter 2 are further evidence that altering acoustic input to the peripheral auditory system modulates central auditory plasticity and is evident at multiple levels of the auditory system. The first group discussed wore a single earplug in the left ear for a period of two weeks, thereby experiencing acoustic attenuation. The second group were given bilateral sound generators to wear for a period of four weeks, representing a form of acoustic enhancement. In both study groups, we documented the effectiveness of these sound treatments in inducing central gain as demonstrated by changes in both acoustic reflexes and the ASSR. The methods described in Chapter 2 were then applied in Chapter 3 but in an older adult population with hearing loss. The subjects wore bilateral hearing devices that functioned as sound generators but were combined with clinically prescribed amplification within the same devices. Using consistent methods, modulation of central gain was demonstrated in both young, normal hearing adults, as well as in older adults with age-related hearing loss. Perceptual and physiological changes in this group may be useful in our understanding of hearing aid acclimatization that are mediated by a central gain mechanism.