Behavioral and Electrophysiological Measures of Speech-in-Noise Perception in Normal Hearing and Hearing Impaired Adults

University of Minnesota Ph.D. dissertation. July 2017. Major: Speech-Language-Hearing Sciences. Advisors: Dr. Yang Zhang, Dr. Peggy B. Nelson. 1 computer file (PDF): vii, 161 pages.Understanding speech in background noise is difficult for many individuals. Mechanisms responsible for variability in speech-in-noise performance across individuals are not well understood. Electrophysiological measures allow for an examination of the timing and strength of neural responses to speech along the auditory pathway and can be used to explore mechanisms underlying reduced speech perception in noise. This dissertation used behavioral and electrophysiological measures to examine the effects of background noise on the neural coding of speech and to identify potential neural correlates of speech perception in individuals with and without hearing impairment. N1-P2, mismatch negativity (MMN), and P3 auditory event-related potentials (AERPs) and associated event-related cortical oscillations in various frequency bands of interest were collected in response to syllable-level stimuli in noise. Behavioral measures consisted of phoneme discrimination and sentence recognition in noise. Results indicated that in addition to impacting averaged AERP responses, background noise disrupted cortical oscillatory rhythms in response to speech in frequency bands of interest across participants. Results also showed that the effects of background noise and hearing impairment on the neural coding of speech are different at different levels of cortical processing. This work revealed that AERPs and associated cortical oscillations represent potential neural correlates of speech perception in noise in individuals with and without hearing impairment. These findings have potential theoretical and practical implications regarding the use of electrophysiological measures for the assessment and rehabilitation of communication difficulties in background noise