One of the few research groups in the nation applying positron emission tomography (PET) to attention deficit hyperactivity disorder (ADHD) describes for the first time how cerebral blood flow patterns differ between adults with and without ADHD when performing difficult attentional tasks.
The School of Medicine group is using three-dimensional PET to provide some of the first glimpses of minute-by-minute changes in brain activity during difficult task performance. The team presented its research at the Society for Neuroscience meeting in San Diego in November.
"I'm interested in how physiology and environment affect ADHD," said first author Julie B. Schweitzer, assistant professor, Department of Psychiatry and Behavioral Sciences. "Children and adults with ADHD are always hyperactive, but in some situations their symptoms cause more problems for themselves and those in their environments. We hope to extrapolate much of the information we glean from adults to children with ADHD."
Schweitzer reports that the goal of this work is to identify then minimize those situations that are particularly taxing to patients.
The Emory group performed 12 PET scans each on 10 young-to-middle aged men. The men were similar to one another, except that five men were diagnosed with ADHD and five were not. The blood flow in the brain of each man was recorded while he performed an auditory vigilance task. Every few seconds for eight minutes, each man was given a single-digit number and asked to add the number to the previous number.
"Differences in how the two groups of subjects processed this information were obvious behaviorally and quantitatively," Schweitzer said.
As the minutes passed, mathematical errors among the men with ADHD increased; errors among the control subjects were minimal. PET scans showed that blood flow in the areas of the brain processing the information remained at high levels for the ADHD patients but tapered off considerably as time elapsed for the non-ADHD men.
The researchers were interested to find that cerebral blood flow in the ADHD men was significantly more active in the visual areas of the brain, rather than the auditory processing areas, as would have been expected.
"This may indicate a difference in strategies the two groups use to perform attentional tasks," Schweitzer said. "The ADHD men who were struggling with the auditory task may have tried to use a visual strategy to help with the task. In fact, that is what ADHD patients reported.
"We hope more research into this area will enable us to teach children with ADHD more effective strategies for when they need to use their attentional skills in school and their everyday environment."
The scans of the men without ADHD were telling as well. The later scans showed a reduction in brain blood flow overall, particularly in auditory processing brain regions, suggesting that the subjects had somewhat "mastered" the task and required less concentration and energy (blood flow) to that cerebral region.
The Emory group is beginning PET studies of the much-prescribed but little understood drug ritalin. While its clinical usefulness is well-documented, its specific mechanism of action is not, the researchers say. They also will be recruiting female subjects for future studies.
-- Lorri Preston