Impaired rich club and increased local connectivity in children with traumatic brain injury : local support for the rich?

Recent evidence has shown the presence of a rich club in the brain, which constitutes a core network of highly interconnected and spatially distributed brain regions, important for high-order cognitive processes. This study aimed to map the rich club organization in 17 young patients with moderate to severe TBI (15.71 +/- 1.75 years) in the chronic stage of recovery and 17 age- and gender-matched controls. Probabilistic tractography was performed on diffusion weighted imaging data to construct the edges of the structural connectomes using number of streamlines as edge weight. In addition, the whole-brain network was divided into a rich club network, a local network and a feeder network connecting the latter two. Functional outcome was measured with a parent questionnaire for executive functioning. Our results revealed a significantly decreased rich club organization (p values<.05) and impaired executive functioning (p<.001) in young patients with TBI compared with controls. Specifically, we observed reduced density values in all three subnetworks (p values<.005) and a reduced mean strength in the rich club network (p=.013) together with an increased mean strength in the local network (p=.002) in patients with TBI. This study provides new insights into the nature of TBI-induced brain network alterations and supports the hypothesis that the local subnetwork tries to compensate for the biologically costly subnetwork of rich club nodes after TBI