Attention-deficit/hyperactivity disorder (ADHD) is the most frequently encountered childhood onset disorder in primary care settings. ADHD is characterized by certain behaviours, most commonly: inattention, hyperactivity, and impulsiveness. Although preliminary research indicates that the biological roots of ADHD may involve certain areas of the brain, the link between the cognitive and behavioral manifestations of ADHD and its neural basis is poorly understood. Research shows that the midbrain’s dopamine system — a neural system associated with reward learning and reward-related behavior (reinforcement learning) — is abnormal in children with ADHD. To date, however, there has been little research regarding exactly how the disturbance of the dopamine system leads to this impaired reinforcement learning. Dr. Clay Holroyd is interested in the neurobiological mechanisms that underlie cognitive control — how people regulate their attention, thoughts, and actions in accord with high-level goals and intentions. Specifically, he is focusing on how people detect and correct their errors and, and how they learn from the consequences of their actions. Currently, ADHD research is an important component of his ongoing research program. Dr. Holroyd is investigating impaired cognitive control, error processing, and reinforcement learning in children with ADHD. Using behavioural experiments and computational modeling, he is researching whether the cognitive and behavioral impairments associated with ADHD are the result of the transmission of abnormal reinforcement learning (RL) signals from the midbrain dopamine (DA) system to the frontal areas of the brain involved in cognitive control. Developing a greater understanding of the link between the neural impairment in ADHD and learning and behavior is an important step towards creating a common and accepted model of ADHD; one that spans multiple levels of analysis, including biology, behavior and cognition. This research will provide a greater understanding of the neurobiological mechanisms that underlie cognitive and could lead to the development of new therapeutic treatments for children with ADHD.