IPN Student Emily Coffey was recently awarded the prestigious 2017 Prix d'excellence de ADESAQ for Distinguished Dissertation. The Association des doyens des études supérieures au Québec (ADESAQ) and Quebec's three granting agencies offer a competition which intends to acknowledge a Ph.D. dissertation which has distinguished itself through its original and significant contribution to a field falling under the responsibility of each granting agency during the previous year. Below is the abstract of Emily's dissertation.
Thesis title: Periodic sound encoding in the human auditory system: variability and plasticity
The human auditory system is made up of a network of processing centres in the brainstem, thalamus, and cortex, which interact with higher-level functions and the sensory and motor systems. Although the coordinated activity of the entire ensemble is responsible for human auditory perception and related behaviour, including language and music, it has been suggested that the fidelity with which important features of sound are encoded and processed in early auditory areas may place limitations on system performance on auditory tasks. In this thesis, we address a set of research questions within the theme of relationships between early sound encoding and higher-level cognitive function, and their respective neural correlates. Throughout these studies, our primary focus is on temporal encoding of periodic sound, as measured using the frequency following response (FFR), an evoked response that has typically been studied using electroencephalography (EEG). The FFR has been related to individual differences in perception and pathology of the auditory system, is malleable to musical and linguistic training, and can be modulated by top-down factors like attention, making it a valuable tool for studying interactions between basic sound processes and higher- level cognition. This thesis contributes to fundamental auditory neuroscience and its methods by clarifying the neural origins of fine periodic encoding, its behavioural meaning, and sources of individual variability. We explored its relationship to long-term training, and to cortical function and structure, using EEG, MEG, fMRI, and diffusion weighted imaging. We also clarified how better quality periodic sound encoding might result in better behavioural performance on complex tasks, particularly speech-in-noise perception. Together, this work improves our understanding of individual differences in periodic sound representation and how it influences complex behaviour. The conclusions in turn may inform strategies for optimizing and remediating faulty auditory system components, via training.