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

• A significant improvement in integration and segregation, marked by a strong initial increase in small-worldness followed by a slowing. • Development of structural segregation diverged along an anterior-posterior axis. • Hemispheric hub edges, through short-range white matter connections between adjacent cortices, exhibited increased regularity and symmetry. • Age-related changes in modularity and number indicate an increase in structural module segregation, characterized by declining modularity and stable composition. 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.