Content area
Abstract
Many processes contribute to the perception of our acoustic environments. We identify and discriminate amongst different types of sounds, including vocalizations, environmental sounds, and other auditory "objects." We also encode complex temporal associations between sounds, which are particularly important for speech and music perception. However, it remains unclear how the brain solves these and other problems, particularly when healthy neural mechanisms are compromised in disease states. In this dissertation, I address these issues through MRI investigations of the human auditory brain. In Chapter II, I describe subregions of auditory cortex that may be specialized for processing specific types of auditory objects and low-level acoustic features. I argue that these auditory cortical subregions, identified using functional MRI (fMRI), are part of a hierarchically organized object-processing pathway in anteroventral auditory cortex. Chapter III addresses how the brain creates associations between sounds as they unfold in time. These fMRI experiments demonstrate that musical sequence learning recruits brain regions previously implicated in motor sequence learning and memory, suggesting that these parts of the brain subserve sequence processing in a generalized manner. Finally, Chapter IV explores neural abnormalities underlying tinnitus, an often debilitating pathological auditory sensation. Using both fMRI to monitor dysfunction and voxel-based morphometry (VBM) to measure anatomical anomalies, these experiments indicate that the auditory and limbic systems contribute to different aspects of this increasingly common, but little-understood, disorder. Taken together, these three studies provide insight into complementary aspects of auditory perception, contributing to our global understanding of the human auditory brain.
