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The findings point to the potential of rfMRI to help provide objectively accurate, early diagnosis of a disorder that affects approximately 5 percent of children and adolescents worldwide. ADHD is a disorder characterized by age-inappropriate degrees of inattention, hyperactivity and impulsivity. Functional MRI studies, which measure brain activity when a person is focused on a particular task, have implicated the brain's frontostriatal circuit, a collection of neural pathways in the frontal lobe of the brain that helps control behavior. However, the specific brain physiology underlying ADHD remains poorly understood. For the new study, researchers used rfMRI, a relatively new technique that assesses neural function when the brain is not focused on a specific task. The technique is useful for exploring the brain's functional organization independent of task performance. The researchers compared rfMRI results in 33 boys with ADHD, ages 6 to 16, with those of 32 similar...

They say findings from their study, published online today in  Neuron , may increase the understanding of underlying causes of ADHD, potentially facilitating the development of more individualized treatment strategies. The scientists looked at dopaminergic neurons, which regulate pleasure, motivation, reward, and cognition, and have been implicated in development of ADHD. They uncovered a receptor system that is critical, during embryonic development, for correct wiring of the dopaminergic brain area. But they also discovered that after brain maturation, a cut in the same receptor, SorCS2, produces a two-chain receptor that induces cell death following damage to the peripheral nervous system. The researchers report that the SorCS2 receptor functions as a molecular switch between apparently opposing effects in proBDNF. ProBDNF is a neuronal growth factor that helps select cells that are most beneficial to the nervous system, while eliminating those that are less favorable i...