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

Abstract

Introduction: Symptoms of attention-deficit/hyperactivity disorder (ADHD) are closely associated with impaired executive function. Medication is the first-line treatment for ADHD, yet its effects on brain function and structure remain unclear. To investigate medication-related brain alterations in children with ADHD, we used functional near-infrared spectroscopy, which captures cortical hemodynamic activity, and structural magnetic resonance imaging, which measures subcortical volume. Methods: We investigated the differences in brain hemodynamic activity between 23 children with ADHD taking medication and 22 children who were not taking medication. Results: 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 group also exhibited a negative correlation between oxygenated hemoglobin and symptom severity, whereas the medicated group showed a positive correlation. Furthermore, abnormal asymmetry of the thalamic volume was reduced in the medicated group compared to the unmedicated group. Discussion: These findings suggest that increased prefrontal activation and reduced thalamic asymmetry may reflect medication-related improvements in inhibitory control in children with ADHD.