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http://hdl.handle.net/11375/28386
Title: | Development of Auditory Brainstem Response in the Big Brown Bat |
Authors: | Groulx, Thomas |
Advisor: | Faure, Paul |
Department: | Psychology |
Keywords: | signal processing;Eptesicus Fuscus;Auditory Brainstem Response;Cross-correlation;Auditory Development |
Publication Date: | 2021 |
Abstract: | Echolocating bats use hearing for passive orientation, alerting functions, and social communication. How bats develop their sense of hearing is an important question that can help us understand hearing in all mammals, including humans. This knowledge is also useful to outline the typical hearing of different animal models to provide information for modeling hearing development. Here, I document the neural progression of hearing in developing pups of the big brown bat, Eptesicus fuscus. Hearing development was tracked by measuring the auditory brainstem response (ABR) at multiple timepoints during pup maturation and evaluating changes in the recorded neural waveforms. Audiograms were measured as the ABR threshold at different sound frequencies. The ABR waveform consists of several peaks and troughs that represent the synchronous and summed responses of ascending auditory neurons between the cochlea and the upper brainstem. To a trained observer, signatures of ABR peaks and troughs indicate whether a stimulus has evoked a reliable neural response. The threshold of audibility was determined by repeatedly presenting pure tone stimuli, starting at a high sound pressure level (SPL) and systematically reducing stimulus level until the recording no longer showed a time-locked response. An advantage of using ABRs is the procedure is a relatively non-invasive, hence it allows for multiple, longitudinal recordings from the same individuals across development. I analyzed a series of ABR recordings looking for changes in waveforms features related to the onset and maturation of hearing in E. fuscus pups. First, I measured changes in the average root mean square amplitude of ABR signals as pups aged. A spectral analysis of ABR waveforms was conducted, focusing on 2 frequency regions of interest. A cross-correlation analysis was used to measure changes in neural response latency as stimulus SPL was varied but also to measure the time-lag evoked by the same stimuli in pups at different ages. My results demonstrate that amplitudes in ABRs increased with pup age and stimulus SPL, and that this effect was frequency dependent, decreasing as the stimulating tone was moved away from frequencies close to the bat’s auditory fovea (i.e. the frequency range of best auditory sensitivity between 20 and 48 kHz). Changes in stimulus SPL affected the latency of ABR signals, although the effect was less pronounced for tones within the bat’s auditory fovea. My research describes the development of the auditory system of the big brown bat as measured by ABRs. The development of bat tuning curves as described by ABRs are compared to those described by behavioural data. |
Description: | The development of hearing within the big brown bat was measured from birth to maturation. Hearing development was measured using the auditory brainstem response (ABR), a multi-featural signal which is widely accepted as a measure of auditory functioning. Two observers found closely matching labels relating to ABR presence/absence and these labels related well to ABR features of interest including root mean square signal amplitude, spectral composition of the evoked signal, as well as relationships to ABRs evoked at other frequencies and amplitudes. The ABR features of interest showed greater sensitivity to stimulus level outside of the acoustic fovea of the bat, which shifted upward in frequency as bat pups matured. |
URI: | http://hdl.handle.net/11375/28386 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Groulx_Thomas_CG_finalsubmission2021Sept_MScThesis.pdf.pdf | 1.66 MB | Adobe PDF | View/Open |
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