Time-Varying Lateralization of Infant White Matter Tracts and the Development of the Corpus Callosum Público
Joe, Elayne (Spring 2022)
Abstract
Background: The corpus callosum (CC) is the largest white matter structure in the brain that influences interhemispheric connectivity and, subsequently, lateralization. However, exactly how the CC influences lateralization and how this relationship emerges in infancy remains unclear. Understanding how the CC develops in relation to lateralization in the typically-developing infant is critical since developmental disorders, such as autism spectrum disorder, dyslexia, and congenital sensorineural hearing loss, have been linked to atypical lateralization in the brain and altered callosal morphology. Thus, this project explores how CC development is associated with the development of lateralization of infant white matter tracts in the first 6 months of life.
Methods: Diffusion MRI data were collected at up to 3 time points between birth and 6 months in N = 78 typically-developing infants. Template-based probabilistic tractography delineated left and right masks for 7 bilateral white matter structures, in addition to the whole-brain, that were selected due to the presence of significant lateralization during infancy. These include the arcuate fasciculus (AF), anterior thalamic radiation (ATR), fornix (Fx), inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), and pyramidal tract from the motor (PTM) and sensorimotor (PTS) cortices. Trajectories of lateralization indices were fit using Functional Principal Components Analyses, and associations between lateralization and fractional anisotropy of the CC splenium (CCs), body (CCb), and genu (CCg) were explored using Functional Linear Regression.
Results: Significant associations were found between the IFOF and CCs, ATR and CCs, ATR and CCb, PTM and. CCb, whole-brain and CCb, and whole-brain and CCg. For the CCs and CCb, CC development and lateralization were positively correlated in the earlier days of infancy and negatively correlated towards the end of the first 6 months of life, whereas this trend was reversed for the CCg.
Discussion: The relationships between CC development and lateralization development were found to be time-varying, indicating that CC development is both positively and negatively associated with lateralization. By studying this relationship within typically-developing infants, our findings may provide a point of comparison for atypical developmental processes, especially early in development, which may have implications for earlier diagnostic criteria in developmental disorders.
Table of Contents
Introduction - 1
Methods - 5
Results - 12
Discussion - 15
Tables and Figures - 22
References - 34
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