Date of Award

Spring 1-1-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Interdepartmental Neuroscience Program

First Advisor

Scheinost, Dustin

Abstract

Lateral preferences are ubiquitously present throughout the body despite its oversimplifications towards handedness. Studies on lateral preferences have therefore been simplified and binarized based on handedness preferences despite incongruencies and reduced proportions of right-preference as other limbs and measures are taken into consideration. In spite of this, studies on brain-laterality preferences that have been simplified and confined towards brain-handedness studies have demonstrated that handedness greatly affects how the brain is functionally organized and that these preferences are linked to high concurrences with other behavioral traits, both normative and psychiatric. For instance, males are more likely to be left-handed than females and prevalence of left-handedness is higher in psychiatric populations critical insights into understanding developmental trajectories that contribute to the rise of certain psychiatric disorders. At present, most studies on handedness and brain development focus on specific regions of interest, leaving whole-brain differences and the influence of other lateral preferences largely unexplored. As such, this limited focus has meant that scientists can only hypothesize about how handedness—and broader laterality preferences—affect brain organization, as the exact mechanisms remain largely unknown. This lack of a comprehensive understanding in brain-handedness associations have thus limited neuroscience studies from correctly controlling for these differences and incorporating left-handed participants in studies, as a result, severely underrepresenting left-handed populations. Moreover, limited perspectives in generalizing handedness towards laterality preferences pervasively offers a biased perspective and an overestimation towards preferences for a specific side given that handedness preferences exhibit stronger preferences towards a specific side than true measures of laterality preferences. The aims set out in this thesis aims to utilize data-driven methods to explore whole brain differences in brain-lateral preferences associations to understand how developmental trajectories in neural networks differ based on these preferences. Using functional magnetic resonance imaging (fMRI) scans and graph theory derived methods, known as functional connectivity, to explore whole brain relationships and connectivity, these studies comprehensively first explore how group differences in handedness affects development of brain circuits. These studies are further expanded towards exploring these differences at a more granular measure, for instance relationships between how handedness is measured, both in a singular cohort and age group as a bench mark before further generalizing to include participants with varying age ranges across the lifespan. Finally, explorations between how handedness compares to other laterality preference measures are made in brain-behavior associations to provide a more comprehensive perspective on further insights other laterality preferences may be able to provide beyond handedness preferences.

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