Children were excluded if they did not meet criteria for ADHD or non-ADHD groups (i.e. children deemed sub-threshold by the clinicians were excluded). Children were also excluded if parent report identified a history of neurological illness, chronic medical problems, sensorimotor handicap, autistic disorder, mental retardation, or significant head trauma (with loss of consciousness), or if they had evidence of psychotic disorder or bipolar disorder on the structured parent psychiatric interview. Children prescribed psychotropic medications other than stimulants were excluded and children prescribed stimulant medications were scanned after a minimum washout of five half-lives (i.e. 24-48 h depending on the preparation). Additional exclusion criteria for control children were: presence of conduct disorder, major depressive disorder, as well as presence of ADHD. Only right-handed children were included in the study.
