61 These regions are more active during rest than during a task, hence the name “default mode” or “task negative” network.62 Figure 4. Development
of functional connectivity. Voxelwise resting-state functional connectivity maps for a seed region (solid black circle) in medial prefrontal cortex—mPFC (ventral: -3, 39, -2). (A) Qualitatively, the resting-state functional connectivity … Using five seeds in distinct regions of the anterior cingulate cortex Inhibitors,research,lifescience,medical it was found that over development, local patterns of connectivity evolved from diffuse to focused, and networks changed from exhibiting mostly local connectivity to see more include more distant brain regions.63 Subjects’ resting state data were able to be used to predict their age—their maturational curve
accounted for more than half of the variation in their data.64 Examining both structural and functional connectivity of DMN regions, it was found that the connectivity of the PCC-mPFC along Inhibitors,research,lifescience,medical the cingulum was the least mature in children.65 Some regions that were poorly connected structurally in children still had strong functional connectivity. This suggests that Inhibitors,research,lifescience,medical the saying “what fires together, wires together”66 may hold on a larger scale—the functional coupling of some brain regions may strengthen their structural connectivity over time. In a cohort of subjects scanned multiple times—both within scan session and between sessions separated by a few Inhibitors,research,lifescience,medical years—it was demonstrated that rsfMRI can reliably map brain networks in children and adolescents.67 A study that focused less on the specific regions connected and more on the quality
of the connections found that children’s functional networks tended to include more voxels and than did those of adults.68 Inhibitors,research,lifescience,medical This supports earlier hypotheses that maturation is marked by a process of refining and “focusing” of brain networks. Neurodevelopmental disorders While we cannot cover all neurodevelopmental disorders, here we review some of the more common or more commonly studied neurodevelopmental disorders (Table II). Autism Autism is a neurodevelopmental disorder characterized by deficits in social interaction and communication, and by repetitive behaviors. The prevalence of autism is estimated to be around 2.5 %69 and is usually diagnosed by Sitaxentan age 3.70 Autism has a partially genetic basis, although the specific mechanisms that contribute to the disorder are complex and are not expected to be the same in all children with autism.71 Structural MRI A number of studies have compared individuals of a specific age group with autism with typically developing individuals; fewer have examined changes in the developmental trajectory associated with autism. In an impressively large study (N=188), Langen et al examined the development of the striatum in autistic and typicallydeveloping individuals.