Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Biomedical Engineering

Supervisor

de Ribaupierre, Sandrine

2nd Supervisor

Eagleson, Roy

Co-Supervisor

Abstract

Multimodal brain imaging allows the study of structure-function relationships of the brain at the individual level, a key subject in basic neuroscience with important applications in neurosurgery. The current thesis aims to better understand these relationships by (1) examining how cortical morphology metrics influence measures of brain function, (2) their visualization in augmented reality (AR), and (3) their application in neurosurgical planning. To achieve these objectives, we made use of multimodal magnetic resonance imaging (MRI) data: diffusion weighted imaging, resting-state functional MRI (rs-fMRI), task-based fMRI, and T1-weighted images. Various metrics were calculated: cortical thickness (CT), blood oxygen level dependent signal variability (BOLDSD), structural connectivity (SC), functional connectivity (FC), etc.. We found that BOLDSD measures are confounded by CT, developed an application to visualize SC and FC in AR, and used rs-fMRI to map language for epilepsy surgery. Overall, these studies provided a better understanding of structure-function relationships in the brain.

Summary for Lay Audience

The human brain is one of the most complex and important organs. Its anatomical structure and its function are inextricably tied to each other in a reciprocal relationship in which structure can shape function and the vice versa. Considering that each person has a unique anatomy, physiology and life experience, it should not come as a surprise that this structure-function relationship is best understood at the individual level. Despite recent advancements in neuroscience, researchers still struggle to understand this relationship and its implications in a clinical setting.

The current thesis aims to explore structure-function relationships of the brain in the setting of basic research and neurosurgery planning. We used multiple distinct but complementary magnetic resonance imaging (MRI) techniques to study these relationships. In the first study, we investigated how cortical morphology metrics (i.e. brain structure measurements) influence a specific measure of brain function called blood oxygen level dependent signal variability (BOLDSD) in older adults. BOLDSD has been previously associated with cognitive health in aging. We found that cortical thickness is a confound to BOLDSD measurements and should be considered in the design of studies. In the second study, we examined structure-function relationships by developing an augmented reality application which allows the person using it to explore brain anatomy in the context of brain connectivity (i.e. structural and functional connections between regions in the brain). This application can be further developed to be used as an education tool for novice surgeons. In the third study, we examined the brain scans of children with epilepsy and used structural and functional MRI methods to preoperatively localize language. This can help the surgeon guide their approach to surgery by avoiding brain regions that may be involved in language.

Overall, this thesis adds to the current knowledge of the relationship between the structure and function of brain in the context of basic neuroscience and neurosurgery applications.

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