PROJECT SUMMARY Attention deficit hyperactivity disorder (ADHD) is one of the most prevalent neurobehavioral disorders present during childhood and adolescence. ADHD associated with profound interpersonal and societal burden, yet the cause of ADHD is unknown. Sleep is an intimate regulator of cognition and behavior and sleep deprivation leads to inattention-like symptoms. One in three children with ADHD have sleep problems, yet the role of sleep in regulating inattention in ADHD is under-investigated. I propose to examine whether sleep contributes to the cause of inattention characteristic to pediatric ADHD. If so, sleep loss may provide a novel yet manageable risk factor in multiple conditions where sleep loss and inattention co-occur (e.g., ADHD, anxiety disorder, bipolar disorder, autism, obsessive compulsive disorder). In this K01 application I propose to address this concern with training in developmental psychopathology and neurobehavioral disorders (e.g., assessment, diagnosis, patient contact), multi-modal neuroimaging in children with such disorders, advanced statistical and analytical techniques (e.g., causal inference modeling), child and adolescent sleep (e.g., sleep disorders co-morbid in ADHD), and child/pubertal development. I propose a research plan that fully capitalizes on this inter- disciplinary training. I will characterize a sample of 68 youngsters (10-13 yo) across a dimension of symptom- level inattention, ranging from asymptomatic to severe attention deficits. Each child will enter a spend three nights in the laboratory: a sleep-rested night of laboratory sleep, a night with sleep restricted to 4 hours, and a full night of recovery sleep. I predict that increasing severity of attention will be associated with structural brain deficits in attention-regulating neuroanatomy that will lead to atypical sleep, and as a result increased vulnerability to sleep loss and decreased sensitivity to the benefits of sleep. If successful this project will greatly expand our knowledge of the role of sleep in ADHD.