Tonotopy as an organizational principle of high-level auditory cortex

Abstract

Audition is one of the core senses, and yet there is relatively little known about the mapping and the processing of sound in human auditory cortex. As audition is one of the essential ways that humans interact with the physical world, being able to expand our knowledge of audition will aid us in not only understanding the basic principles of brain functioning but also in better treating medical conditions relating to audition. To address this lack of knowledge, this thesis set out to answer a fundamental question of auditory processing in the brain. Is the frequency of sound a driving principle in controlling where sound is processed in auditory cortex? To answer this question, we conducted sweeping-tone and category localizer fMRI experiments in 11 different participants to explore auditory processing and representation in human cortex. Our sweeping- tone experiment allowed us to make a tonotopic map of frequency preference in primary auditory cortex (PAC). The category localizer experiment then enabled us to find category (voice and instrument) selective regions in auditory cortex and compare their preferred frequencies with the frequencies of sounds from different categories. Overall, our findings suggest that sound selective regions show biases for the frequencies of sounds that they sample. This investigation gave us important insights into the development and processing of audition, a realm of cognitive neuroscience that is relatively not well understood.