Age, sex, and puberty related development of the corpus callosum: a multi-technique diffusion MRI study.

The corpus callosum is integral to the central nervous system, and continually develops with age by virtue of increasing axon diameter and ongoing myelination. Magnetic resonance imaging (MRI) techniques offer a means to disentangle these two aspects of white matter development. We investigate the profile of microstructural metrics across the corpus callosum, and assess the impact of age, sex and pubertal development on these processes. This study made use of two independent paediatric populations. Multi-shell diffusion MRI data were analysed to produce a suite of diffusion tensor imaging, neurite orientation dispersion and density imaging, and apparent fibre density (AFD) metrics. A multivariate profile analysis was performed for each diffusion metric across ten subdivisions of the corpus callosum. All diffusion metrics significantly varied across the length of the corpus callosum. AFD exhibited a strong relationship with age across the corpus callosum (partial η2 = 0.65), particularly in the posterior body of the corpus callosum (partial η2 = 0.72). In addition, females had significantly higher AFD compared with males, most markedly in the anterior splenium (partial η2 = 0.14) and posterior genu (partial η2 = 0.13). Age-matched pubertal group differences were localised to the splenium. We present evidence of a strong relationship between apparent fibre density and age, sex, and puberty during development. These results are consistent with ex vivo studies of fibre morphology, providing insights into the dynamics of axonal development in childhood and adolescence using diffusion MRI.