EMBARGOED FOR RELEASE UNTIL 4 PM ET, July 17, 2019
Study Finds Kids with ADHD Have Differences in Part of Brain that Controls Movement
Race Car Game Shows Delay in Responding to “Stop Cues”
MINNEAPOLIS -
Children with attention deficit hyperactivity disorder (ADHD) may have differences in the brain that limit appropriate responses to “stop cues” in a race car game, according to a study published in the July 17, 2019, online issue of Neurology®, the medical journal of the American Academy of Neurology. “The findings of our research suggest that the severity of a child’s ADHD symptoms may be associated with diminished ability of the brain to engage appropriately in critical tasks,” said study author Donald L. Gilbert, MD, MS, of Cincinnati Children’s Hospital Medical Center in Ohio and a Fellow of the American Academy of Neurology. The study involved 131 children ages 8-12. Of the group, 66 children had ADHD. Those taking stimulants for ADHD temporarily stopped, and long-acting ADHD medicines were not allowed. Researchers first measured “resting” brain activity in the motor cortex, the part of the brain that controls voluntary movement. To do this, they used transcranial magnetic stimulation (TMS); TMS is delivered with a non-invasive device placed over the scalp. Magnetic fields are delivered from the device to stimulate nerve cells in the brain. By stimulating the area of the brain that controls movement, or the motor cortex, researchers were able to generate electrical activity in muscles and measure differences in that activity for each participant as they were asked to react to commands to move and to stop moving. When stimulated by TMS, brains of kids with ADHD generated weaker inhibitory or “braking,” signals. At rest, the children with ADHD had an inhibition level of 43 percent, compared to a level of 54 percent for those without ADHD. This reflects the brains baseline capacity to “put the brakes” on competing processes so it can focus on the task at hand, Gilbert said. To test the brain’s responses to commands to “Go” and “Stop,” researchers asked the children to play a race car computer game specially designed for the study. Seated comfortably in a chair, the children were asked to push down a button with their index finger to drive the car and then at a precise moment, in just under one second, decide whether or not to stop the car. To measure both the brain’s “braking” activity and its “engagement” in the game, TMS pulses were administered to the brain during the races, and responses were measured using an electrode on their index finger. The children with ADHD had impaired brakes and reduced engagement. Compared to children without ADHD, children with ADHD had 40 percent less inhibitory signaling to the finger during driving, and 45 percent less inhibitory signaling during stopping. Overall brain engagement was 10 percent lower in ADHD, and this reduction correlated very strongly with severity of ADHD symptoms and accuracy in the race car game. “These results may provide a road map for better identifying distinct subtypes of ADHD as well as for monitoring how well treatment is working for children with ADHD,” said study co-author Stewart H. Mostofsky, MD, of Kennedy Krieger Institute in Baltimore, Md., and a member of the American Academy of Neurology “More research is needed to understand how these motor findings are associated with specific behavioral features of ADHD and how they are associated with response to different treatments.” A limitation of the study was that many of the children with ADHD had been taking medications prior to the study and stopping the drugs during the study may not eliminate the possibility of some drug effects. The study was supported by the National Institutes of Health and the National Institute of Mental Health. Learn more about ADHD at BrainandLife.org, home of the American Academy of Neurology’s free patient and caregiver magazine focused on the intersection of neurologic disease and brain health. Follow Brain & Life® on Facebook, Twitter and Instagram.