Maturation of topological organization of brain networks in male adolescent rats: A longitudinal FDG-PET study

Recent studies have found developmental alterations of the brain during the adolescent period. However, maturation-related changes of the topological properties in brain networks are unexplored so far. We therefore used fluoro-D-glucose positron emission tomography (FDG PET) to explore the maturation-related topological metabolic changes in brain networks from adolescence to adulthood with a longitudinal study in rats (male, n = 6), followed by a graph theoretical analysis. Our results showed reduced normalization characteristic path length and increased small world index of brain networks. Specifically, we found that relative to adulthood, in the adolescent stage rats had significantly increased nodal centrality in right entorhinal cortex, left frontal association cortex, and cerebellum, areas relating to memory, executive function and higher cognitive control and motor control; and significantly reduced nodal centrality in left superior colliculus and left retrosplenial cortex. These findings suggest that moving from adolescence to adulthood, networks of the brain mature accompanied by reassignment of hub regions to increase network efficiency. These results provide an animal model of brain network maturation from adolescence to adulthood which are relevant for understanding of development of psychiatric disorders during adolescence or transition from adolescence to adulthood.