Researchers have discovered a connection in the brain that might be responsible for causing attention deficit-hyperactivity disorder (ADHD). Earlier studies found differences in areas of the brain that control attention and hyperactivity. Symptoms for attention deficit hyperactivity disorder vary widely. Some with ADHD are unable to sit still. They may also act impulsively and can be easily distracted. Completing tasks can be difficult.

Dominique Potter recalls that her daughter Chloe had tremendous difficulty doing her homework. "It took hours … the math, anything would just take hours," Potter said. Dr. Nora Volkow of the US National Institute on Drug Abuse says the inattention and impulsivity that characterize ADHD could be caused by a disruption in the transmission of dopamine – a key mood regulator that helps cells communicate.

"Dopamine is considered a neurotransmitter that is crucial for our ability to perceive rewards and to be motivated in our behavior," she explains. Dr. Volkow says if someone cannot perceive a reward they may have difficulty completing tasks. The study used images taken at Brookhaven National Laboratory in New York. Researchers compared the brain pathways that transmit dopamine of 53 ADHD adults to those of 44 adults without the disorder.

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"There was a lower concentration of dopamine markers in the brain of individuals with ADHD, specifically in the areas of the brain that are involved with reward and motivation," Dr. Volkow said. She says the disruption in the transmission of dopamine was directly related to the severity of inattention. The study suggests that creating ways to make school and work assignments more rewarding to people with ADHD could improve their performance. The study was published by the Journal of the American Medical Association. (VOA/JC)