AUTHOR=Saad Jacqueline Fifi , Griffiths Kristi R. , Korgaonkar Mayuresh S. 

TITLE=A Systematic Review of Imaging Studies in the Combined and Inattentive Subtypes of Attention Deficit Hyperactivity Disorder

JOURNAL=Frontiers in Integrative Neuroscience

VOLUME=14

YEAR=2020

URL=https://www.frontiersin.org/journals/integrative-neuroscience/articles/10.3389/fnint.2020.00031

DOI=10.3389/fnint.2020.00031

ISSN=1662-5145

ABSTRACT=<p><bold>Objective:</bold> Insights to underlying neural mechanisms in attention deficit hyperactivity disorder (ADHD) have emerged from neuroimaging research; however, the neural mechanisms that distinguish ADHD subtypes remain inconclusive.</p><p><bold>Method:</bold> We reviewed 19 studies integrating magnetic resonance imaging [MRI; structural (sMRI), diffusion, functional MRI (fMRI)] findings into a framework exploring pathophysiological mechanisms underlying the combined (ADHD-C) and predominantly inattentive (ADHD-I) ADHD subtypes.</p><p><bold>Results:</bold> Despite equivocal structural MRI results, findings from fMRI and DTI imaging modalities consistently implicate disrupted connectivity in regions and tracts involving frontal striatal thalamic in ADHD-C and frontoparietal neural networks in ADHD-I. Alterations of the default mode, cerebellum, and motor networks in ADHD-C and cingulo-frontoparietal attention and visual networks in ADHD-I highlight network organization differences between subtypes.</p><p><bold>Conclusion:</bold> Growing evidence from neuroimaging studies highlight neurobiological differences between ADHD clinical subtypes, particularly from a network perspective. Understanding brain network organization and connectivity may help us to better conceptualize the ADHD types and their symptom variability.</p>