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Interhemispheric asymmetry of regional cerebral blood flow in prepubescent boys with attention deficit hyperactivity
D D Langleben1, G Austin, G Krikorian
1The Department of Psychiatry, Treatment Research Center, University of Pennsylvania, 3900 Chestnut Street, Philadelphia, PA 19104, USA. langlebe@mail.med.upenn.edu
Insights
Children with severe attention deficit hyperactivity disorder (ADHD) show reversed prefrontal cortex asymmetry during response inhibition tasks. This suggests right prefrontal cortex dysfunction in ADHD, impacting inhibitory control.
Area of Science:
- Neuroscience
- Developmental Psychology
- Medical Imaging
Background:
- The prefrontal cortex exhibits structural and functional asymmetry in healthy individuals.
- Response inhibition is typically associated with greater right prefrontal cortex activation.
- Attention deficit hyperactivity disorder (ADHD) is linked to impaired response inhibition and altered brain asymmetry.
Purpose of the Study:
- To investigate functional interhemispheric asymmetry during response inhibition in children with ADHD.
- To explore how motor hyperactivity levels correlate with prefrontal cortex asymmetry in ADHD.
Main Methods:
- Children with ADHD were categorized into three groups based on motor hyperactivity.
- Regional cerebral blood flow (rCBF) was measured using SPECT during a response inhibition task (RIT).
- Functional asymmetry was assessed by comparing rCBF between cerebral hemispheres using voxel-wise subtraction of mirrored scans.
Main Results:
- Children with severe hyperactivity displayed a left>right rCBF asymmetry in the prefrontal cortex.
- Significant left>right occipitoparietal asymmetry was also observed in the severe hyperactivity group.
- These findings indicate a reversal of typical prefrontal asymmetry in severe ADHD.
Conclusions:
- The reversed prefrontal asymmetry in severe ADHD supports the hypothesis of right prefrontal cortex dysfunction.
- Altered functional brain asymmetry during response inhibition may be a key feature of ADHD.
- Understanding these asymmetries can inform ADHD diagnosis and treatment strategies.
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.
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