Changes in Anatomical Brain Connectivity between Ages 12 and 30: a Hardi Study of 484 Adolescents and Adults

Graph theory can be applied to matrices that represent the brain’s anatomical connections, to better understand global properties of anatomical networks, such as their clustering, efficiency and “small-world” topology. Network analysis is popular in adult studies of connectivity, but only one study – in just 30 subjects – has examined how network measures change as the brain develops. Here we assessed the developmental trajectory of graph theory metrics of structural brain connectivity in a cross-sectional study of 484 subjects, aged 12 to 30. We computed network measures from 70x70 connectivity matrices of fiber density generated using whole-brain tractography in 4Tesla 105-gradient high angular resolution diffusion images (HARDI). All network measures changed with age, and both age and age 2 effects were identified. The strongest age effect was seen for the normalized clustering (lambda), which decreased across development. HARDIbased connectivity maps are sensitive to the remodeling and refinement of structural brain connections as the human brain develops. Index Terms – graph theory, high angular resolution diffusion imaging (HARDI), tractography, network analyses, development, structural connectivity