Fixel-Based Diffusion Magnetic Resonance Imaging Reveals Novel Associations Between White Matter Microstructure and Childhood Aggressive Behavior.

BACKGROUND: Childhood aggression has been linked to white matter abnormalities, but research has been inconsistent with regard to both regions of alterations and directionality of the associations. We examined white matter microstructure correlates of aggression using a novel diffusion imaging analysis technique, fixel-based analysis, which leverages connectivity and crossing-fiber information to assess fiber bundle density. METHODS: The sample included 70 children with aggressive behavior and 25 healthy control children without aggressive behavior. Aggression was measured by the parent-rated Aggressive Behavior scale of the Child Behavior Checklist. Fixel-based analysis was conducted at the whole-brain and region-of-interest levels, including the uncinate fasciculus, inferior longitudinal fasciculus, fornix, cingulum bundle, and genu, body, isthmus, and splenium of the corpus callosum. RESULTS: Whole-brain analysis of covariance revealed that children with aggressive behavior, relative to control children, had lower fiber density in a cluster of limbic and cortical pathways, including the inferior fronto-occipital fasciculus, fornix, middle cerebellar peduncle, and superior thalamic radiations (familywise error-corrected p < .01), and had higher fiber density in the corpus callosum (body and splenium) (familywise error-corrected p < .05). Region-of-interest analyses showed decreased fiber density in cingulum bundles associated with aggression. These effects were independent of age, sex, IQ, symptoms of attention-deficit/hyperactivity disorder, medications, and head motion. In children with aggressive behavior, co-occurring callous-unemotional traits and anxiety did not moderate the association between aggression and white matter density. CONCLUSIONS: Diminished white matter density in pathways connecting limbic and cortical regions is associated with childhood aggression. Abnormal interhemispheric connectivity via corpus callosum may also reflect a potential neural mechanism involved in aggression.

Anger Rumination is Associated with Restricted and Repetitive Behaviors in Children with Autism Spectrum Disorder.

Children with autism spectrum disorder (ASD) are reported to have greater levels of anger rumination than typically developing children. This study examined anger rumination in children with ASD in comparison to children with disruptive behavior disorder without ASD. We also tested if anger rumination is associated with aggression and the core ASD symptoms of restricted and repetitive behaviors (RRBs). This study included three groups of children aged 8-16 years: 63 had ASD (ASD group), 79 had disruptive behavior disorder (DB group), and 40 healthy controls (HC). ASD and DB groups showed greater anger rumination relative to the HC group. Anger rumination was associated with RRBs in children with ASD, suggesting the link to core ASD symptoms.