Date of Award

Spring 1-1-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Speech, Language & Hearing Sciences

First Advisor

Phillip M. Gilley

Second Advisor

Christine Yoshinaga-Itano

Third Advisor

Pui-Fong Kan

Fourth Advisor

Jeff Coady

Fifth Advisor

Albert E. Kim

Abstract

During auditory processing of linguistic information listeners must overcome many challenges in order to interpret the meaning of the spoken language. Speech is rarely delivered without noise, and the auditory system must rapidly interpret the incoming speech signal. In this study I examined the effects of multitalker babble on speech perception in typical adults and children during a word recognition task. Continuous EEG was collected from 64 scalp channels while participants completed the tasks. EEG for each participant were analyzed using a continuous wavelet transform (CWT) using a fast-Fourier convolution. CWTs were computed at 256 log-spaced frequencies ranging from 3Hz to 100Hz. Intertrial phase clustering was computed across conditions. ITPC profiles were computed separately for noise and non-noise conditions, and statistical tests were performed for comparison.

Adults and children both had significant effects of noise on the N1 component, while neither had effects of noise on the P3 component amplitude suggesting that early components are more important for speech perception in noise. Phonotactic probability had an effect on the P3 component at the left temporal electrode site. While word frequency and noise had an effect on the earlier N1 component. The adults showed a significant effect of noise versus quiet in ITPC of the alpha and theta frequency ranges following stimulus onsets at temporal channel regions, which may suggest a slight right hemisphere dominance for processing in noise. Children show a similar pattern; however, the ITPC for children are not significant at the group level in the left hemisphere, which suggests that phase clustering is developing from right to left. This suggests that children are still developing consistent processing mechanisms and that they may have more temporal jitter in the phase onset of alpha and theta oscillations. These results highlight the importance limiting noise for speech perception and processing in typically developing children to improve auditory speech perception, and likely have implications for children with language learning difficulties depending on how there auditory system develops.

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