Executive Function

Another area of our research involves developmental changes in executive functioning (e.g. response inhibition) and reward processing (e.g. delay of reinforcement). We have shown that there are larger age-related differences in the brain for response inhibition than for visual search, and have suggested that this could be due to slower maturation of the frontal lobes critical for executive functioning. We have also shown that children with attention deficit hyperactivity disorder (ADHD) exhibit larger brain abnormalities during response inhibition than for visual search, suggesting that a central deficit in ADHD may be in executive function. As with dyslexia, ADHD is a heterogeneous population and there are probably multiple pathways to the disorder. In fact, other investigators have shown that some children with ADHD have a behavioral deficit in executive functioning whereas others have a deficit in reward processing. We are currently examining whether children with ADHD that have a behavioral deficit in response inhibition have abnormalities in ventro-lateral prefrontal cortex and dorsal striatum whereas those with a behavioral deficit in reward processing have abnormalities in orbito-frontal cortex and ventral striatum. Not only will this work allow for a basic understanding of brain development, it will have important implications for accurate diagnosis and pharmacological intervention in children with ADHD.