Author Description

This dissertation, "Functional Magnetic Resonance Imaging Investigation of Auditory Processing in the Midbrain" by Peng, Gao,, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: The inferior colliculus (IC) is the major auditory nucleus in the midbrain. It integrates all ascending auditory projections from multiple brainstem nuclei and receives massive descending projections from the cortices. Blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is a noninvasive technique that can measure the hemodynamic responses as neural correlates throughout a nucleus with high spatial and temporal resolution. The objectives of this doctoral work were to develop and apply novel fMRI methods, for in vivo assessment of the auditory midbrain functions in rodent models. Firstly, fMRI combined with an oddball auditory stimulation paradigm was applied to investigate the role of the IC in detecting deviant sound. For two different sound tokens, BOLD responses to the deviant (with lower occurrence probability) were significantly higher than to the standard (with higher occurrence probability). The results demonstrated the involvement of the IC in deviance detection and revealed the highly adaptive nature of a substantial population of neurons in medial IC, where the strongest responses to the deviant were observed. Secondly, fMRI combined with two-tone stimulation paradigm was applied to investigate the IC responses to ultrahigh frequency (UHF) sounds. UHF vocalizations, but not pure tones at similar UHFs, evoked robust IC BOLD responses. Furthermore, IC BOLD responses were detected when