Effect of medication on the rostrolateral prefrontal oxygenation and thalamic volume asymmetry in youths with ADHD

Abstract Symptoms of attention deficit hyperactivity disorder (ADHD) are associated with impaired executive functions. Some functional magnetic resonance imaging (fMRI) studies on medication effects have provided positive evidence of neuroactivation patterns in children with ADHD; however, they should be extended to functional near-infrared spectroscopy (fNIRS)-based examination of the neuropharmacological effects of medication. We investigated the differences in brain hemodynamic activity between 23 children with ADHD taking medication and 22 children who were not taking medication. Compared with the medicated ADHD group, the unmedicated ADHD group showed significantly reduced activation in the left rostrolateral prefrontal cortex (channel 9, p = 0.01; channel 13, p = 0.02) and dorsolateral prefrontal cortex (channel 14, p = 0.01). The unmedicated ADHD group exhibited a negative correlation between oxygenated hemoglobin (HbO) and symptom scores, while the ADHD with medication group exhibited a positive correlation. Moreover, the abnormal asymmetry of the thalamic volume was reduced in children with ADHD receiving medication compared to those not receiving medication (p = 0.02). Current findings suggest that left rostrolateral prefrontal activation and reduced thalamic asymmetry are important for inhibitory control, and that the activity of this region is restored by ADHD medication.