Date of Graduation

Spring 2016

Degree

Doctor of Audiology

Department

Communication Sciences and Disorders

Committee Chair

Wafaa Kaf

Keywords

compound action potential, frequency-place map, kainic acid, apical injection, otoacoustic emissions

Subject Categories

Speech Pathology and Audiology

Abstract

The present study aims to evaluate the origin of compound action potential (CAP) responses in the guinea pig ear using the following method. Pipettes were sealed into the cochlear apex of 26 guinea pigs to inject ototoxic pharmaceuticals that inhibit nerve responses without affecting cochlear function. The rate of the injection was adjusted once each minute to account for variations in the diameter of the cochlea and to maintain a steady flow of pharmaceuticals. CAP measurements collected at around 90-second intervals using tone burst stimuli during the injections allowed evaluation of the neural responses over time. Responses to higher stimulation levels revealed a later ablation time, indicating they originate from a more basal, higher frequency region than 2 kHz. CAP abolition rates revealed variations between individual ears. Additionally, distortion-product otoacoustic emission (DPOAEs) measurements were collected to evaluate cochlear response. Findings showed that the injection did not alter DPOAE response amplitudes, indicating it had no effect on cochlear mechanics. These findings provide insight into irregular spatial origins of cochlear responses, and therefore an irregular frequency-place map, in individual ears.

Copyright

© Kaitlyn M. Kennedy

Open Access

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