Prefrontal Brain Activation in Subtypes of Attention Deficit Hyperactivity Disorder: A Functional Near-Infrared Spectroscopy Study

Abstract

According to clinical symptoms, attention deficit and hyperactivity disorder (ADHD) is categorized into three groups: the predominantly inattentive subtype (ADHD-I),the predominantly hyperactive-impulsive subtype (ADHD-HI), and the combined subtype (ADHD-C). Recent advances in neuroimaging have demonstrated new approaches for assessing the ADHD subtypes with underlying pathophysiology.This study aims to examine the hemodynamic response and reaction time (RT) in healthy children and the ADHD subtypes as measured by functional near-infrared spectroscopy (fNIRS) during an auditory oddball attention task. The sample was made up of 40 children divided into four groups: control group (n=14), ADHD-I group (n=9), ADHD-HI group (n=6), and ADHD-C group (n=11). The target responses were identified and were grand-averaged for each participant. Right prefrontal cortex hemodynamic responses and groups performances on RT were compared between subtypes and between controls and subtypes. Functional near-infrared spectroscopy indicated that while control subjects exhibited higher activation than all ADHD subtypes, the ADHD subtypes did not differ from one another. Relative to control subjects, a longer RT was observed in all ADHD subtypes. The ADHD-I group showed significantly longer RTs compared to the ADHD-HI and ADHD-C groups.This study can bring a new perspective to the continuing controversy about ADHD subtypes, and the findings may help in the evaluation of fNIRS, RT, and RT variability studies in ADHD.