Exploring Microstructure Asymmetries in the Infant Brain Cortex: A Methodological Framework Combining Structural and Diffusion Mri.

The development of the human brain is a complex process that starts during early pregnancy and extends until the end of adolescence. In parallel to morphological changes in brain size and gyrification, several microstructural changes occur in the cortex, such as the development of dendritic arborization, synaptogenesis and pruning, and fiber myelination. Magnetic Resonance Imaging (MRI) can provide indirect markers of these mechanisms through the mapping of quantitative parameters. Here, we used a dedicated methodological framework to perform reliable voxel-wise analyses over the infant cortex. The examination of hemispheric asymmetries in microstructure required careful alignment of morphological asymmetries through registration of native and flipped brains using a 2-step matching strategy of sulci (DISCO approach) and cortical ribbon (DARTEL approach). We tested the potential of this approach in 1-to-5-month-old infants, with a focus on cortical longitudinal diffusivity from Diffusion Tensor Imaging (DTI). This enabled us to unravel different microstructural evolution patterns of specific sensorimotor and language regions in the left and right hemispheres.