Hyperactivity in motor response inhibition networks in unmedicated children with attention deficit-hyperactivity...

Hypo/reduced activity in motor response inhibition (RI) cerebral networks was recently proposed as a promising specific neurobiological marker of attention deficit-hyperactivity disorder (ADHD). Before adopting such a pattern as a key diagnosis tool, we aim to replicate in an independent study the mechanisms underlying reduced RI-related activity in ADHD, after controlling for potentially confounding effects.

In this fMRI study, we investigated the neural networks mediating successful and failed motor RI in children with ADHD and typically developing children (TDC) using the stop-signal task (SST) paradigm.

In contrast to hypofrontality predictions, children with ADHD exhibit increased neural activity during successful response inhibition in an RI-related brain network encompassing the indirect and/or hyperdirect pathways between the basal ganglia and cortex. Voxel-based morphometry analyses have further evidenced reduced grey matter volume in the left caudate in children with ADHD, which paralleled higher functional responses. Finally, connectivity analyses disclosed tighter coupling between a set of cortical regions and the right caudate as well as the right IFG, networks involved in successful RI.

Hypo/reduced activity in RI cerebral networks in children with ADHD cannot at this time be considered as a systematic biomarker for ADHD.