title: Disorder-specific inferior prefrontal hypofunction in boys with pure attention-deficit/hyperactivity disorder compared to boys with pure conduct disorder during cognitive flexibility.
abstract: BACKGROUND
  Problems with cognitive flexibility have been observed in patients with attention deficit hyperactivity disorder (ADHD) and in patients with conduct disorder (CD), characterized by the violation of societal rules and the rights of others. Functional magnetic resonance imaging (fMRI) of cognitive switching, however, has only been investigated in patients with ADHD, including comorbidity with CD, finding frontostriatal and temporoparietal underactivation. This study investigates disorder-specific functional abnormalities during cognitive flexibility between medication-naïve children and adolescents with noncomorbid CD and those with noncomorbid ADHD compared to healthy controls.
  
  
  METHODS
  Event-related fMRI was used to compare brain activation of 14 boys with noncomorbid, childhood-onset CD, 14 boys with noncomorbid ADHD, and 20 healthy comparison boys during a visual-spatial Switch task.
  
  
  RESULTS
  Behaviorally, children with ADHD compared to children with CD had significantly slower reaction times to switch compared to repeat trials. The fMRI comparison showed that the patients with ADHD compared to both controls and patients with CD showed underactivation in right and left inferior prefrontal cortex. No disorder-specific brain underactivation was observed in patients with CD. Only when compared with controls alone, the disruptive behavior group showed reduced activation in bilateral temporoparietal and occipital brain regions.
  
  
  CONCLUSIONS
  The findings extend previous evidence for disorder-specific underactivation in patients with ADHD compared to patients with CD in inferior prefrontal cortex during tasks of inhibitory control to the domain of cognitive flexibility. Inferior prefrontal underactivation thus appears to be a disorder-specific neurofunctional biomarker for ADHD when compared with patients with CD.
authors.affiliation: Department of Child Psychiatry, MRC Center for Social, Genetic and Developmental Psychiatry, Institute of Psychiatry, King's College, London, United Kingdom. k.rubia@iop.kcl.ac.uk
authors.forename: Katya
authors.initials: K
authors.lastname: Rubia
authors.forename: Rozmin
authors.initials: R
authors.lastname: Halari
authors.forename: Ana
authors.initials: A
authors.lastname: Cubillo
authors.forename: Abdul-Majeed
authors.initials: AM
authors.lastname: Mohammad
authors.forename: Stephen
authors.initials: S
authors.lastname: Scott
authors.forename: Michael
authors.initials: M
authors.lastname: Brammer
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000378:metabolism / Q000503:physiopathology*; D001931:Brain Mapping / Q000379:methods; D002648:Child; D003071:Cognition / Q000502:physiology*; D019955:Conduct Disorder / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009483:Neuropsychological Tests / Q000592:standards; D017397:Prefrontal Cortex / Q000033:anatomy & histology / Q000378:metabolism / Q000503:physiopathology*