Abnormal Structure and Function of Parietal Lobe in Individuals With Attention Deficit Hyperactivity Disorder (ADHD): A Systematic Review Study

Abstract

Introduction: Abnormal brain structure and function have been reported in individuals with attention deficit hyperactivity disorder (ADHD). This study investigated the parietal lobe structure and function alteration in individuals with ADHD. Methods: In this systematic review, we searched English papers in accordance with the PRISMA (the preferred reporting items for systematic reviews and meta-analyses) approach. Studies were published between January 2010 and May 2021. Our search was conducted in two parts. Our first search was in July 2020, and our final search was in June 2021. A literature search identified 20 empirical experiments. Results: Functional magnetic resonance imaging (MRI) studies generally reported low activity and poor connectivity; structural MRI studies reported less gray matter in this lobe, and an echo study reported atrophy. In addition, electroencephalographic studies reported less connectivity of the parietal lobes in ADHD. Furthermore, the transcranial direct current stimulation intervention has shown that activation of this lobe improves attention and executive functions in children with ADHD. Finally, a deep transcranial magnetic stimulation study has demonstrated that activation of this lobe improves working memory. Conclusion: Functional and structural alteration of the parietal cortex has been reported in ADHD, which has a causal relationship with cognitive impairments. In sum, all included studies reported abnormal structure, function, or connectivity of the parietal lobe or improvement of cognitive functions with parietal lobe stimulation.