| dc.description.abstract | The world is replete with acoustic signals that fluctuate over time and emanate from different spatial locations. Consequently, the brain is imbued with mechanisms for encoding information about these temporal and spatial features, the functioning of which is degraded by noise-induced hearing loss (NIHL). NIHL can be overt, or hidden from clinical diagnostic measures, which has motivated researchers to evaluate the sensitivity of different measures of temporal and spatial processing, to design more sensitive diagnostic tools. Neurophysiological studies have gained insight into how the auditory pathway encodes temporal and spatial information, and how it is degraded by NIHL. However, these studies often characterize encoding in isolation from perceptual decision-making, and typically use non-primate species, leaving open translational questions regarding human and nonhuman primates. Finally, studies of temporal and spatial processing in nonhuman primates (NHPs) almost exclusively take place in the cerebral cortex, leaving open fundamental questions about the functioning of the extensive subcortical circuitry in the NHP auditory pathway.
This dissertation proceeds on three fronts to enhance knowledge of these topics, specifically 1) to apply a perceptual decision-making framework to NHP behavioral data through the use of signal detection theory and models of temporal integration, 2) to extend knowledge of the awake, behaving NHP auditory pathway to the subcortical regions of the cochlear nucleus and inferior colliculus, and 3) to evaluate measures of temporal and spatial processing in a NHP model of NIHL, providing a translational bridge that was previously unavailable in these two domains of auditory processing. The main results of this approach indicate 1) that there are far-reaching similarities in NHP and human auditory temporal processing in both detection and discrimination paradigms, 2) that temporal processing previously attributed to the cortex may be better explained using subcortical responses, and 3) that behavioral measures of temporal and spatial processing provide differentially sensitive measures of two forms of NIHL. Together these results provide knowledge of fundamental neural processing, and lay the groundwork for translational studies in humans with hidden and overt NIHL. | |
