November 20, 2008
Hyperactive Boys Have Smaller Basal Ganglia In Brain

Boys with Attention Deficit Hyperactivity Disorder (ADHD) have brain shapes that differ from those kids who aren't hyperactive.

November 17, 2008 (Baltimore, MD)A study published today in the online advance edition of The American Journal of Psychiatry for the first time reveals shape differences in the brains of children with ADHD, which could help pinpoint the specific neural circuits involved in the disorder. Researchers from the Kennedy Krieger Institute in Baltimore, Md. and the Johns Hopkins Center for Imaging Science used a new analysis tool, large deformation diffeomorphic mapping (LDDMM), which allowed them to examine the precise shape of the basal ganglia. The study found boys with ADHD had significant shape differences and decreases in overall volume of the basal ganglia compared to their typically developing peers. Girls with ADHD did not have volume or shape differences, suggesting sex strongly influences the disorder's expression.

Once again another discovery is made possible by a new measurement technique. The ability to more accurately scan and measure brain volumes allows scientists to discern differences in brain shapes that are correlated with behavioral differences.

Previous studies examining the basal ganglia in children with ADHD were limited to volume analysis and had conflicting results, with some reporting a smaller volume and some reporting no difference in volume. LDDMM provides detailed analysis of the shape of specific brain regions, allowing for precise examination of brain structures well beyond what has been examined in previous MRI studies of ADHD. In this study, LDDMM was used to map the brains of typically developing children in order to generate a basal ganglia template. This is the first reported template of the basal ganglia. After creating LDDMM mappings of the basal ganglia of each child with ADHD, statistical analysis was conducted to compare them to the template.

In this study, the initial volume analysis revealed boys with ADHD had significantly smaller basal ganglia volumes compared with typically-developing boys. Moving beyond the standard volume analysis, the LDDMM revealed shape abnormalities in several regions of the basal ganglia. Comparison of the standard volume and LDDMM analysis of girls with ADHD and their typically developing peers failed to reveal any significant volume or shape differences.

The multiple shape differences found in boys with ADHD suggests that the disorder may not be associated with abnormalities in one specific neural circuit. Rather, it appears the disorder involves abnormalities in parallel circuits, including circuits important for the control of complex behavior and more basic motor responses, such as hitting the brake pedal when a traffic light turns yellow. Findings revealing abnormalities in circuits important for basic motor response control may be crucial to understanding why children with ADHD have difficulty suppressing impulsive actions.

If this finding holds up it suggests that permanent reduction in ADHD behavior might require large scale changes in brain shape.

Share |      Randall Parker, 2008 November 20 11:50 PM  Brain Development


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