Abnormal wiring of the structural connectome in adults with ADHD

Current knowledge of white matter changes in large-scale brain networks in adult attention-deficit/hyperactivity disorder (ADHD) is scarce. We collected diffusion-weighted magnetic resonance imaging data in 40 adults with ADHD and 36 neurotypical controls and used constrained spherical deconvolution-based tractography to reconstruct whole-brain structural connectivity networks. We used network-based statistic (NBS) and graph theoretical analysis to investigate differences in these networks between the ADHD and control groups, as well as associations between structural connectivity and ADHD symptoms assessed with the Adult ADHD Self-Report Scale or performance in the Conners Continuous Performance Test 2 (CPT-2). NBS revealed decreased connectivity in the ADHD group compared to the neurotypical controls in widespread unilateral networks, which included subcortical and corticocortical structures and encompassed dorsal and ventral attention networks and visual and somatomotor systems. Furthermore, hypoconnectivity in a predominantly left-frontal network was associated with higher amount of commission errors in CPT-2. Graph theoretical analysis did not reveal topological differences between the groups or associations between topological properties and ADHD symptoms or task performance. Our results suggest that abnormal structural wiring of the brain in adult ADHD is manifested as widespread intrahemispheric hypoconnectivity in networks previously associated with ADHD in functional neuroimaging studies. Although it is well-established that widespread changes in large-scale brain networks underlie ADHD, little is known about the aberrancies in the complex structural brain networks that pertain at adulthood. Knowledge of structural changes in adult ADHD would be important as the symptom presentation of the disorder changes considerably across the life-span. We found that abnormal structural brain wiring in adults with ADHD is manifested as widespread hypoconnectivity in unilateral networks, and attention task performance is associated with a left-frontal network across all participants. White matter abnormalities in overlapping brain networks have been reported also in children with ADHD, but emerging evidence in adults proposes some changes in the neuropathology of ADHD from childhood to adulthood.