Tract-specific white matter microstructure associated with early cognitive development in infants.

Background and purpose: Early infancy is characterized by rapid and regionally specific changes in white matter microstructure, which can be quantified using diffusion tensor imaging (DTI). We examined whether diffusion-derived microstructural measures during early postnatal life are associated with emerging cognitive functions. Material and methods: Twenty-three infants from the UNC Brain Connectome Project underwent 3T MRI between 2 weeks and 3 months of age. Fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD) were extracted from major white matter tracts using atlas-based tractography. Cognitive performance was assessed using the Mullen Scales of Early Learning (MSEL). Associations between tract-specific DTI metrics and cognitive scores were evaluated. Results: Tract-specific associations were observed between white matter microstructure and cognitive outcomes. Diffusion metrics in the corticothalamic tract and fornix were associated with gross and fine motor performance, while FA, AD, and RD in the optic tract and optic radiation were related to visual reception. Language measures were associated with diffusion properties of the arcuate and uncinate fasciculi. Several corpus callosum subdivisions also showed significant associations with early learning outcomes. Conclusion: These findings demonstrate that early postnatal white matter microstructure is selectively associated with emerging cognitive functions, supporting the utility of DTI for investigating brain-behavior relationships during early infancy.