Cortical Gray Matter in Attention-Deficit/Hyperactivity Disorder: A Structural Magnetic Resonance Imaging Study

Abstract

ObjectivePrevious studies have shown smaller brain volume and less gray matter in children with attention-deficit/hyperactivity disorder (ADHD). Relatively few morphological studies have examined structures thought to subserve inhibitory control, one of the diagnostic features of ADHD. We examined one such region, the pars opercularis, predicting a thinner cortex of the inferior frontal gyrus (IFG) in children with ADHD.MethodStructural images were obtained from 49 children (24 control; 25 ADHD combined subtype) aged 9 though 15 years. Images were processed using a volumetric pipeline to provide a fully automated estimate of regional volumes of gray and white matter. A further analysis using FreeSurfer provided measures of cortical thickness for each lobe, and for 13 regions in the frontal lobe.ResultsRelative to controls, children with ADHD had smaller whole brain volume and lower gray matter, but not white matter, volumes in all lobes. An analysis of frontal regions showed a significant interaction of group by region. Planned contrasts showed bilateral thinner cortex in the pars opercularis in children with ADHD.ConclusionsChildren with ADHD showed both diffuse and regional gray matter abnormalities. Consistent with its putative role in response inhibition, the cortex of the pars opercularis was thinner in children with ADHD who, as expected, had significantly poorer inhibitory performance on a Go/No-go task. These differences held for both hemispheres raising the possibility that a developmental abnormality of IFG might drive development of inhibition difficulties.

Attention Deficit Hyperactivity Disorder

“…A study by Shaw et al (2006) shows that children with ADHD have cortical thinning throughout the cortex, but particularly in prefrontal regions associated with attention and other executive functions. Other groups have also shown cortical thinning in the frontal regions of individuals with ADHD (Depue et al 2010;McAlonan et al 2007;Batty et al 2010). Depue et al (2010) also showed that disrupted performance in behavioral tasks in ADHD (such as response inhibition, response variability, and processing speed) are associated with reduced volume in the inferior frontal gyrus.…”

Reduced subcortical volumes among preschool-age girls and boys with ADHD

“…By school-age, ADHD is associated with widespread structural brain abnormalities including smaller total cerebral volumes (Friedman and Rapoport, 2015), reductions in total gray matter volumes (Batty et al, 2010), and more localized anomalies in prefrontal and premotor areas (Dirlikov et al, 2015; Mahone et al, 2011b; Shaw et al, 2006), and subcortical structures (Ellison-Wright et al, 2008; Frodl and Skokauskas, 2012; Hoogman et al, 2017; Nakao et al, 2011; Norman et al, 2016). Despite the fairly consistent evidence of frontal lobe anomalies in individuals with ADHD, it is not clear whether these volumetric reductions are secondary to developmental deviations in subcortical regions.…”

Anterior cingulate cortex and symptom severity in attention-deficit/hyperactivity disorder.

“…Existing studies indicate symptoms of ADHD may be functionally related to reductions in cortical thickness. For example, children with ADHD who performed significantly worse than healthy controls on a Go/No-go inhibition test were found to have reduced cortical thickness of the IFG (Batty et al, 2010). The authors speculated that cortical thinning in the IFG provides more evidence that inhibitory dysfunction in ADHD is due in part to prefrontal cortex abnormalities.…”