ADHD: Part 2

Yesterday in an article from the Good Morning America show on ADHD, the studied showed that the differences were particularly prominent for boys with ADHD who showed nearly four times as much mirror overflow than typically developing boys on one of the two measures used in the study.

“This study used quantitative measures to support past qualitative findings that motor overflow persists to a greater degree in children with ADHD than in typically developing peers,” said Dr. Mostofsky. “The findings reveal that even at an unconscious level, these children are struggling with controlling and inhibiting unwanted actions and behavior. Studying motor control weakness gives us a window to understanding the similar challenges that children with ADHD face in controlling more complex behavior, which can lead to improved diagnosis and treatment.”

In a second study, the researchers investigated motor control in children with ADHD further by measuring activity within the motor cortex, the part of the brain that controls voluntary movement. Researchers used Transcranial Magnetic Stimulation (TMS) to apply mild magnetic pulses for brief durations to trigger muscle activity in the hand, causing hand twitches. Researchers performed 60 trials, with single or paired pulses to measure the level of muscle activity and monitored the resulting brain activity, called short interval cortical inhibition (SICI). Overall, children with ADHD showed a substantial decrease in SICI, with significantly less inhibition of motor activity during the paired pulse stimulation compared to typically developing children. The degree of inhibition in children with ADHD, measured by SICI, was 40 percent less than typically developing children. Furthermore, within the ADHD group, less motor inhibition (decreased SICI) correlated with more severe symptoms. The measure of SICI not only predicted motor impairment in ADHD children but also robustly predicted their behavioral symptoms as reported by parents. The findings suggest that reduced SICI may be a critical biomarker of ADHD.