Subdivision of Superior Longitudinal Fasciculus in Human Neonatal Brain

Abstract

The superior longitudinal fasciculus (SLF) is a complex associative tract comprising of three distinct subdivisions in the fronto-parietal cortex, each presenting different anatomical connectivity and different functional roles. However, the subdivision of SLF was hampered by limitations of data quality and tractography methods, and many studies on white matter development often consider the SLF as a single entity. The exact anatomical trajectory and developmental status of each sub-bundle of the human SLF in neonatal period remain poorly understood. In this work, we investigated the morphological characteristics and maturation degree of SLF each branch using the diffusion MRI (dMRI) data of 40 healthy term neonates from the Developing Human Connectome Project (dHCP) database. An advanced single shell 3-tissue constrained spherical deconvolution (SS3T-CSD) algorithm was used to ensure the successful separation of the SLF three branches (SLF I, SLF II and SLF III). In addition, diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) parameters values of the three subcomponents of SLF were measured quantitatively. The fiber morphology and connectivity of SLF sub-bundles in neonatal brain were nicely revealed in our study. Furthermore, the comparison results of parameters values supported that the maturation of SLF three segments was heterochronic. Further multiple comparison results indicated that the dorsal SLF II was less mature than the ventral SLF III and the former may involve in higher-level cognitive functions. Our findings can provide new anatomical basis for early diagnosis and treatment of related diseases caused by aberrant development of SLF.