Hau J, et al. - In 61 autism spectrum disorder (ASD) and 54 normally developing children and adolescents, researchers used probabilistic tractography to examine white matter fibers of the cingulate cortex by distinguishing its deep intra-cingulate bundle (cingulum proper) and short rostral anterior, caudal anterior, posterior, and isthmus cingulate U-fibers. In the ASD group, they observed an atypical age-related decrease in right posterior cingulate U-fiber volume; this seemed to be driven by an abnormally large volume in younger children. Findings revealed a negative association of history of repetitive and restrictive behavior with right caudal anterior cingulate U-fiber volume, connecting cingulate motor areas with neighboring gyri. Aberrant development in U-fiber volume of the right posterior cingulate gyrus could account for functional anomalies detected in this area, such as in the default mode network.