Arjun Sethi1, Valerie Voon2, Hugo Critchley1, Neil A Harrison1, and Mara Cercignani1
The substantia nigra/ventral tegmental area (SN/VTA) is central to the modulation of dopaminergic networks implicated in Attention Deficit Hyperactivity Disorder (ADHD). However, little is known of its specific contribution to the disorder. Whilst motivational abnormalities and impulsivity are known to be related to the structure, it is not clear whether SN/VTA subcomponents differentially contribute to these deficits. Using diffusion MRI tractography parcellation of the SN/VTA, we show that increased waiting impulsivity in ADHD is related to the microstructure of the mesolimbic SN/VTA, whilst trait motivation is related to the nigrostriatal component. Unlike previous reports in unmedicated ADHD, we detect no motivational abnormalities in this medicated cohort. However, we report that patients who have been medicated longer show alterations in microstructure consonant with increased motivation.