White matter myelination during early infancy is explained by spatial gradients and myelin content at birth

Abstract

Development of myelin, a fatty sheath that insulates nerve fibers, is critical for brain function. Myelination during infancy has been studied in postmortem histology, but such data cannot evaluate the developmental trajectory of the white matter bundles of the brain. To address this gap in knowledge, we (i) obtained longitudinal diffusion MRI measures and quantitative MRI measures of T1, which is sensitive to myelin, from newborns to 6-months-old infants, and (ii) developed an automated fiber quantification method that identifies bundles from dMRI and quantifies their T1 development in infants. Here we show that both along the length of each bundle and across bundles, T1 decreases from newborns to 6 months-old's and the rate of T1 decrease is inversely correlated with T1 at birth. As lower T1 indicates more myelin, these data suggest that in early infancy white matter bundles myelinate at different rates such that less mature bundles at birth develop faster to catch-up with the other bundles. We hypothesize that this development reflects experience-dependent myelination, which may promote efficient and coordinated neural communication. These findings open new avenues to measure typical and atypical white matter development in early infancy, which has important implications for early identification of neurodevelopmental disorders.

Creatine in the fetal brain: A regional investigation of acute global hypoxia and creatine supplementation in a translational fetal sheep model

“…Early and accelerated abnormal maturation of white matter has been observed in adolescents with autism spectrum disorder (Ben Bashat et al, 2007), therefore the increased myelin maturation may indicate an increased susceptibility to neurodevelopmental disorders with sensory disabilities. However, recent work supports the idea that increased in utero myelin maturation is coupled with a reduced rate of maturation after birth, meaning overall myelination remains balanced (Grotheer et al, 2022), and thus the increased myelin maturation may have no long-term effects or rather improved cognition (Chevalier et al, 2015). Regardless, further studies with and without increased in utero creatine exposure are required to understand these myelin maturation processes and subsequent consequences on neurodevelopment.…”

Establishing the functional relevancy of white matter connections in the visual system and beyond

“…Next, within the same individual’s native brain space, a whole-brain white matter tractogram is created using dMRI data. The whole-brain tractogram is then classified into bundles (e.g., using automatic tools Yeatman et al 2012 ; Garyfallidis et al 2018 ; Grotheer et al, 2021a ; Kruper et al 2021 ). Next, the classified bundles are “intersected” with the fROI to isolate only those streamlines within each bundle that connect to that fROI, which generates the functionally defined white matter sub-bundles (fSuB) of that fROI.…”