BME PhD Proposal: Brian Flynn

The Role of Temporal Information for Pitch in the Inferior Colliculus of Rabbit

Supervised by Professor Laurel Carney

Abstract

Pitch is a fundamental attribute of sound, yet remains poorly understood. Timing information, in the form of intervals between action potentials, is a potential way for pitch to be encoded at low levels of the auditory system. However, the upper limit of the temporal representation of pitch quickly decreases in higher auditory centers. One fundamental question that has long challenged temporal theories of pitch is how the auditory system might make use of precise timing information found in early auditory centers. Previous studies have suggested a mechanism similar to autocorrelation as a possible means for interpreting timing information, but the neural circuits required for such an operation are unlikely to exist. It is hypothesized that known neural mechanisms such as coincidence detection and periodicity tuning could be used to transform timing information into a rate representation. Furthermore, it is hypothesized that the inferior colliculus is likely involved in such a transformation. Through a combination of physiology, behavioral and modeling studies, we will test our hypothesized physiologically-plausible timing-to-rate transformation mechanism. Concurrently, we will characterize the response of neurons in the inferior colliculus to pitch stimuli, looking specifically for indications of a timing-to-rate transformation. Finally, the results of behavioral thresholds for rabbits on pitch discrimination tasks will be collected and compared to estimated neural discrimination thresholds. This work will result in a better understanding of pitch perception, and more generally, the role of timing information in the auditory system. Such knowledge will lead to improved assistive-listening devices, such as hearing aids and cochlear implants, or suggest the development of novel therapeutic techniques.