A new analysis tool - large deformation diffeomorphic mapping (LDDMM) - was used in the study which was carried out by researchers from the Kennedy Krieger Institute in Baltimore, USA, and the Johns Hopkins Centre for Imaging Science.

The new tool allowed the researchers to examine the precise shape of the basal ganglia.

The study found that boys with ADHD had significant shape differences and decreases in overall volume of the basal ganglia compared to their typically developing peers. In the case of girls with ADHD, however, such volume or shape differences were not found.

Previous studies examining the basal ganglia in children with ADHD analysed volume only, with conflicting results - some reported a smaller volume and some reported no difference in volume.

The current study, using 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.

The study involved the use of LDDMM 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.

Researchers examined 47 children between the ages of eight and thirteen, with ADHD. Children with ADHD who had a history of other neuropsychiatric diagnoses including conduct disorder, mood disorder, generalized anxiety disorder, separation anxiety disorder and/or obsessive-compulsive disorder were excluded from the study. None of the children with ADHD had a learning disability or a history of speech/language disorders.

Researchers compared the LDDMM mappings of children with ADHD to their typically developing peers, and then went a step further by repeating the analysis separately for boys and girls.

The initial volume analysis revealed boys with ADHD had significantly smaller basal ganglia volumes compared with typically-developing boys. The LDDMM also revealed shape abnormalities in several regions of the basal ganglia.

Comparison of the 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 behaviour 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.

"This study represents a major advancement in our ability to examine the neuroanatomic features of ADHD and other developmental disorders," said Dr. Stewart H. Mostofsky, senior study author and a pediatric neurologist in the Department of Developmental Cognitive Neurology at the Kennedy Krieger Institute.

"Using LDDMM, we can more accurately measure the impact of ADHD on brain development, which will not only bring us closer to unlocking the biological basis of the disorder, but help us better diagnose and treat patients."

Potential next steps include research that carefully examines whether the brain abnormalities found in this study can predict certain behavioural features of ADHD.

Future studies will also examine structural features associated with the ability to compensate and respond to therapy. The researchers also plan to use LDDMM analysis on children in a wider age range to see if changes in the basal ganglia occur over time. (Source: ScienceDaily)