Focusing on the unfocused:the functional and structural neural correlates of attention deficit/hyperactivity disorder

Abstract

Attention deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder categorized by symptoms of inattention, hyperactivity, or both, and is often diagnosed in childhood. However, its diagnosis can be difficult due to variability and subjectivity, leaving hope for neural biomarkers to help identify the disorder through imaging techniques. The present study correlated the resting state functional connectivity (rsFC) and white matter integrity in children with measures of ADHD to examine whether functional and structural differences were associated with the disorder. Special attention was paid to the default mode network (DMN) and the frontoparietal network (FPN), which have been implicated in ADHD in past research. Surprisingly, ADHD was associated with differences in rsFC between brain hemispheres, with the left hemisphere showing decreases in rsFC and the right showing increases. ADHD measures were also correlated with increased connectivity between hemispheres. Changes in functional networks were mixed and could support the idea of an aberrant relationship between the DMN and FPN in ADHD. Supplemental analyses then examined these correlations within gender subgroups. Interestingly, females showed more decreases in functional connectivity associated with ADHD, while males showed more increases. When analyzing structural changes across the whole sample, white matter analyses surprisingly only showed one region associated with ADHD. However, when examined within each gender, many areas displayed changes in white matter integrity associated with symptoms of the disorder, with females showing increases in white matter integrity and males showing decreases. Though several limitations of the study call for further research, the present findings may point to neural correlates of ADHD that can support the effort of creating more objective and standardized diagnostic practices in the future. Further uncover pieces of the process until a new, and more complete, word learning theory can be created.