Electroencephalographic characteristics of attention-deficit/hyperactivity disorder subtypes

Abstract

Introduction: Attention-Deficit/Hyperactivity Disorder (ADHD as a neurodevelopmental disorder includes three subtypes predominantly inattentive (ADHD-I), predominantly impulsive/hyperactive (ADHD-H), and predominantly combined (ADHD-C) that has formed a heterogeneity disorder due to differences in pathology and syndrome. This study aimed to evaluate the Electroencephalographic (EEG) characteristics of ADHD subtypes. Methods: Subjects included 61 boys (7-12 years old, normal intelligence) with ADHD (ADHD-I, N= 25; ADHD-H, N=14 and ADHD-C, N=22) and 43 typically developing children (TDC). The groups were matched for IQ- and age. Children were investigated regarding Child Behavior Checklist and brain electrical activity during eyes-closed resting state (i.e. EEG power in delta (1-4 Hz), Theta (4-8 Hz), Alpha (8-12 Hz) and Beta (12-30Hz) frequency bands. Statistical analysis included a 2x2 factorial design by the additive model. Results: Theta/Beta ratio was higher in all ADHD subtypes, especially the ADHD-I subtypes, compared to normal children. Besides, in the ADHD-I subtype, theta activity was higher and beta activity was lower than Theta. No significant difference found between the groups in delta and alpha activity. Conclusion: According to these results, EEG markers can better distinguish the ADHD-I subtype, which can be explained within the framework of the maturational lag model of the central nervous system.