Behavior in Children With Attention Deficit Hyperactivity Disorder and in Healthy Volunteers

The purpose of this study is to determine how the brain controls motor activity in children with attention deficit hyperactivity disorder (ADHD). The inability to control one s behavior is an important symptom of many psychiatric illnesses. The stop signal paradigm which involves withholding a motor response to a go signal, has proved useful in assessing uncontrolled behavior in children with ADHD and other disorders. This study will use a stop signal paradigm in order to evaluate the ability of children with and without ADHD to control their motor behavior. A magnetic resonance imaging (MRI) scan will be used to study how the brain works during specific activities. This study will evaluate the stop signal paradigm in three groups of people: healthy children, children with ADHD, and healthy adults. This study comprises two sub-studies: a behavioral study in which participants perform simple activities and an MRI study. Participants will be asked to stop any over-the-counter medication 5 days before entering the behavioral or MRI study. Children with ADHD will be asked to stop taking medication for ADHD 72 hours before the study. All participants will have a medical history and a psychiatric evaluation (for children, both parents and children provide information for the assessment). Participants in the MRI study will also have physical examinations and blood and urine tests. All children will undergo intelligence tests; and those with ADHD will have tests to confirm the diagnosis. The parents of child participants will complete an autism screening questionnaire.