| Over the last decade, the human auditory brainstem response (ABR) has been fruitfully examined toward elucidating the subcortical encoding of sounds in individuals who have demonstrated a range of listening abilities, from auditory experts to those with auditory processing deficits. The ABR, which reflects synchronous activation of neural generators along the brainstem, is well-suited to examine the subcortical encoding of complex auditory stimuli (e.g., speech) in humans because it can be recorded noninvasively with scalp electrodes and is capable to representing acoustic features of brief time-varying cues with remarkable precision. Until recently, the understanding of the brainstem's contribution in accurate auditory perception and the extent to which it is experience dependent has been limited, particularly in healthy, young adults. The purpose of this dissertation was to explore neural correlates of auditory perceptual ability and the impact of auditory training on the subcortical representation of sounds. These studies validated the use of the speech-evoked ABR as a uniquely sensitive and stable measure in examining auditory processing abilities and revealed the biological mechanisms underlying speech-in-noise perceptual ability. Furthermore, by investigating the impact of two auditory training programs in this population of normal hearing, young adults, we demonstrated continued malleability of perception and neural encoding of speech in adulthood. Predictive relationships were also found between pre-training brainstem response magnitude and amount of training-related perceptual improvement, thus offering an important clinical metric to help identify individuals who would benefit most from auditory training. Taken together, these studies strengthened the theoretical and practical utility of the speech-evoked ABR in objectively assessing its active role in auditory perception and learning. |
