Maturation and reorganization of structural connectivity in infants within half a year

Although brain networks have been extensively investigated, the structural network refinement in the early postnatal period remains under-researched, a period during which axons undergo overproduction, elimination, and myelination, which may lead to alterations in the topology of intercortical connections. A total of 104 preterm infants with few complications were enrolled in the current study. The whole-brain tractography weighted by fiber density was performed for each participant using the second-order integration over the fiber orientation distribution method, which was then sifted to 1 million streamlines. The successive changes in the structural connectivity of infants were examined. The findings indicated a notable improvement in integration and segregation, characterized by a rapid initial increase in small-worldness followed by a deceleration, which is associated with the differential maturation of short- and long-range white matter. Global clustering coefficients increased with age, while node degree exhibited variability: frontal regions showed an increase, whereas temporoparietal-occipital regions demonstrated a decrease, indicating earlier maturation of the latter. Hemispheric hub edges, through short-range white matter connections between adjacent cortices, exhibited increased regularity and symmetry, potentially attributable to the earlier maturation of short-range fibers. Age-related changes in modularity and number indicate an increase in structural module segregation, characterized by declining modularity and stable composition, which reflects a distinct phase of connectivity reorganization. This study improves our understanding of early brain network development by identifying key topological maturation trends in the structural brain networks of early infants.