Efficiency of the prefrontal cortex during working memory in attention-deficit/hyperactivity disorder.

Previous research has demonstrated that during task conditions requiring an increase in inhibitory function or working memory, children and adults with attention-deficit/hyperactivity disorder (ADHD) exhibit greater and more varied prefrontal cortical (PFC) activation compared to age-matched control participants. This pattern may reflect cortical inefficiency. We examined this hypothesis using a working memory task in a group of adolescent girls with and without ADHD. Functional magnetic resonance imaging was used to investigate blood oxygenated level-dependent signal during a working memory task for 10 adolescents from each group, ages 11 to 17 years. We analyzed brain-behavior relationships with anatomically defined regions of interest in the PFC and primary motor cortex. The relationship between brain activity in the dorsolateral PFC and ventrolateral PFC and memory retrieval speed differed by group membership, whereby comparison girls had a more efficient brain-behavior relationship than girls with ADHD. There were no such group differences in brain-behavior relationships for primary motor cortex. These findings lend support to the idea that cognitive and behavioral deficits experienced by children and adolescents with ADHD may in part be related to relatively low efficiency of PFC function.