The relationship between neuropsychological measures of inhibition and sustained attention and structural brain differences in the regions of the caudate and the frontal region was examined in males with attention deficit disorder with hyperactivity (ADD/H).

Ten males with ADD/H (aged 8-17) and 11 male controls (aged 9-18) participated in a neuropsychological evaluation and had a magnetic resonance imaging scan.

As had been reported previously by these authors, the children with ADD/H were found to have reversed asymmetry of the head of the caudate, smaller volume of the left caudate head, and smaller volume of the white matter of the right frontal lobe. Children with ADD/H were found to score more poorly on measures of inhibition and sustained attention but not on measures of IQ, achievement, or motor speed. Comparison of neuropsychological measures and brain structure measures indicated a significant relationship between reversed caudate asymmetry and measures of inhibition and externalizing behavior; i.e., children with reversed caudate asymmetry performed more poorly on measures of inhibition regardless of group membership. Poorer performance on sustained attention tasks was related to smaller volume of the right-hemispheric white matter.

There is emerging evidence that compromised brain morphology of selected regions is related to behavioral measures of inhibition and attention.