Behavioral performance predicts grey matter reductions in the right inferior frontal gyrus in young adults with combined type ADHD

Abstract

Optimized voxel-based morphometry (VBM) was used in the present study to investigate morphometric differences between young adults with combined type Attention Deficit/Hyperactivity Disorder (ADHD) and a well-matched control group. Investigations examined differences on a between-group whole brain level, as well as how individual differences in behavioral performance predicted grey matter differences. Although a whole brain analysis revealed no significant differences between ADHD and control individuals, ADHD but not control individuals exhibited reduced grey matter volume in the right inferior frontal gyrus (rIFG), predicted by poorer behavioral performance on all three measures. A subsequent region-of-interest approach revealed lower grey matter volume in the rIFG in ADHD compared to control individuals. These results suggest that young adults with ADHD show morphometric differences in inferior prefrontal regions, as compared to controls. These morphometric differences are related to disruptions in performance on behavioral tasks that frequently have been reported to be affected in individuals with ADHD.

Figure 1

Z scores for all three behavioral performance composite measures by group: PS = Processing Speed, RI = Response Inhibition, RV = Response Variability. * indicates group level significance at p≥0.05 (df = 20, 30; Control, ADHD individuals, respectively).

Figure 2

Significant results (p<0.05, df 30) of grey matter morphometry correlated with the composite measures of: 2a) PS (Processing Speed; yellow/red) in the anterior insula and rIFG, 2b) RI (Response Inhibition; blue) in the rIFG, 2c) RV (Response Variability, green) in the rIFG and 2d) superior parietal lobule and 2e) an overlay of all three significant findings, highlighting the localization within rIFG (red circle) in ADHD individuals. Figure 2f–h shows the masks used to extract grey matter volume in the 2f) rIFG-Total (red), 2g) rIFG-Opercularis (green), rIFG-Triangularis (blue), rIFG-Orbitalis (pink) and 2h) the superior parietal lobule (yellow). All images are shown in radiological convention (right on left side of image).