Date of Award
12-20-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Advancements in non-invasive imaging have enabled extensive research into higher-order cognitive functions of the brain. Functional Magnetic Resonance Imaging (fMRI) has provided valuable insights into brain networks underlying various cognitive processes. However, limitations such as confined environments and scanner noise pose challenges for fMRI to be broadly applicable across all demographics and experimental conditions, especially in speech and language studies. Because of this, there is a need for complementary techniques that can help understand the brain as it functions during everyday scenarios. High Density Diffuse Optical Tomography (HD-DOT) is an emerging functional near-infrared spectroscopy-based technique with comparative advantages over fMRI, as it is quiet and conducive to naturalistic imaging. Work from our lab has established HD-DOT as a surrogate for fMRI in many ways. My dissertation takes this further by developing methods to improve the utility of HD-DOT with ecologically valid experimental paradigms and enhance its ability to understand the individual brain with precision. I do so by 1) studying the cognitive phenomena of effortful listening in natural speech and speech as heard through cochlear implants, 2) developing precision-focused methods for HD-DOT, and 3) expanding the reach of HD-DOT through open-source data sharing. 1. Standard neuroimaging paradigms of speech have relied on simplified representations of speech as their experimental stimuli. These lack the contextual information present in everyday speech. Due to this, extrapolating functional responses to isolated individual words might not be the same as brain activity during naturalistic language processing. I attempt to study this by comparing how brain responses differ when speech varies in clarity (clear vs. simulated cochlear implant speech) and complexity (words vs. narratives). This contributes to the domain of understanding speech processing in individuals with Cochlear Implants, an understudied population due to contraindications with MRI. 2. Precision based fMRI studies have been tremendous in informing individual level differences as they increase the signal-to-noise in a single-subject level and maximizes the power to detect individual-level differences in functional connectivity and within-person changes over time. I present precision HD-DOT (pHD-DOT) as a feasible and preferable approach for future HD-DOT based studies. A direct clinical implication of this approach is to optimize high-reliability and multi-session imaging to investigate implant induced cortical plasticity. 3. A key aspect of scientific research is sharing ideas and results with the wider audience. I have curated an HD-DOT dataset of naturalistic viewing with the goal that the broader neuroimaging community can utilize it. This is done by demonstrating the usability of volumetric data collected using HD-DOT with standard fMRI data analysis techniques.
Language
English (en)
Chair
Joseph Culver
Committee Members
Jonathan Peelle; Dennis Barbour; Janine Bijsterbosch; Joseph O'Sullivan; Tamara Hershey