Interhemispheric asymmetry of regional cerebral blood flow in prepubescent boys with attention deficit hyperactivity disorder

Abstract

The prefrontal cortex is asymmetric in both structure and function. In normal subjects, the right prefrontal cortex is activated more than the left during response inhibition. Patients with attention deficit hyperactivity disorder (ADHD) have impaired response inhibition and altered structural interhemispheric asymmetry. This study was conducted to examine the functional interhemispheric asymmetry during response inhibition in children with ADHD. Subjects were divided into three groups according to the level of motor hyperactivity. Blood flow tracer (99m)Tc-ethyl cysteinate dimer was injected while subjects were performing a response inhibition task (RIT), followed by single photon emission computerized tomography (SPECT). After three-dimensional reconstruction, filtering and smoothing, individual scans were morphed to a template. Three average group images were created from individual scans. Each average group image was subtracted voxel-by-voxel from its mirror image to compare the regional cerebral blood flow (rCBF) in the right and left cerebral hemispheres, yielding images of significant interhemispheric rCBF asymmetry. The severe hyperactivity group exhibited most prefrontal left>right rCBF asymmetry and left>right occipitoparietal asymmetry. Reversal of functional prefrontal asymmetry in boys with severe motor hyperactivity supports the hypothesis of right prefrontal cortex dysfunction in ADHD.

Animal models of attention deficit/hyperactivity disorder (ADHD): a critical review

“…Both basal ganglia and frontal lobe volumes correlate with impaired attention and inhibition (Casey et al 1997;SemrudClikeman et al 2000). Finally, methylphenidate increases the reduced blood flow in prefrontal regions of individuals with ADHD (Langleben et al 2002;Lou et al 1984Lou et al , 1989. DA and NA are important neurotransmitters in these brain regions, and a dysfunction of these neurotransmitters appears to be likely.…”

“…Even more interesting is the fact that the Animal models of attention deficit/hyperactivity disorder (ADHD) 3 reduction in blood flow in these regions is reversed by methylphenidate (Langleben et al 2002;Lou et al 1984Lou et al , 1989. In a PET study, Zametkin et al (1990) found a reduced glucose metabolism in striatum, thalamus, hippocampus, cingulate regions and most prominently in the premotor and superior PFC.…”

Attention-Deficit/Hyperactivity Disorder and Attention Networks

“…One reported MPH increased rCBF in the DLPFC, caudate, and thalamus bilaterally in previously treatment-naive children and adolescents with ADHD (Kim et al, 2001). Another study showed medication withdrawal had measurable brain effects, highlighting the need to better define drug washout periods for both pharmacoimaging and pathophysiology studies (Langleben et al, 2002). A resting state PET study with scans performed 3 weeks apart found the off-MPH condition was associated with relatively higher rCBF in the precentral gyri, caudate, and claustrum; whereas MPH increased rCBF in the cerebellar vermis (Schweitzer et al, 2003).…”

Effects of methylphenidate on resting-state brain activity in normal adults: an fMRI study

“…It also indicated that ADHD symptom improvement after MPH is associated with the normalization of reduced orbitofrontal activity [26] . Using SPECT, Langleben et al found that chronic MPH treatment decreased the extremely high rCBF in the motor, premotor, and anterior cingulate cortices in ADHD [27] . Based on restingstate SPECT, Cho et al [28] found that non-responders to MPH had higher rCBF in the left anterior cingulate cortex, left claustrum, right anterior cingulate cortex, and right putamen, and lower rCBF in the right superior parietal lobule, compared to the responders.…”