Executive Function

Another area of our research involves developmental changes in executive functioning (e.g. response inhibition and working memory). 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. We are currently examining the influence of the size of reward and the timing of feedback on working memory tasks. In adults, we have established neural correlates of “time discounting” or the devaluation of delayed rewards and of the “choking effect” or performance under pressure created by large rewards. Most importantly, we have shown that activation for “time discounting” and the “choking effect” in the nucleus accumbens is systematically related to activation in the working memory network, suggesting a crucial role of the reward network in working memory functioning. We are in the process of testing the prediction based on behavioral literature that “time discounting” should be larger in younger participants and in those with ADHD due to a steeper delay of reinforcement gradient. Although the behavioral literature is not as extensive on the “choking effect”, we expect greater choking in older participants and in those without ADHD because pressure consumes resources in higher working memory individuals.