title: Rethinking a right hemisphere deficit in ADHD.
abstract: BACKGROUND
  Early observations from lesion studies suggested right hemisphere (RH) dysfunction in ADHD. However, a strictly right-lateralized deficit has not been well supported. An alternatively view suggests increased R > L asymmetry of brain function and abnormal interhemispheric interaction. If true, RH pathology in ADHD should reflect interhemispherically networked and overactivated functioning. The authors evaluated these assertions.
  
  
  METHODS
  Four elements of lateralized brain function were measured: LH specialized, RH specialized, LH with interhemispheric processing (LH/IH), and RH with interhemispheric processing (RH/IH). Next, the authors tested their association with cognitive ability, psychiatric comorbidity, and sibling correlations in 79 children with ADHD.
  
  
  RESULTS
  RH/IH processing was uniquely associated with other outcome measures. There were no associations for independent RH or LH function alone.
  
  
  CONCLUSIONS
  Interhemispherically networked RH processing is critical in ADHD. In addition, lack of association between LH specialized processing and cognitive ability (especially for verbal cognitive tasks) supports increased RH mediation of task processing.
authors.affiliation: UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA 90024, USA. sig@ucla.edu
authors.forename: T Sigi
authors.initials: TS
authors.lastname: Hale
authors.forename: Sandra K
authors.initials: SK
authors.lastname: Loo
authors.forename: Eran
authors.initials: E
authors.lastname: Zaidel
authors.forename: Grant
authors.initials: G
authors.lastname: Hanada
authors.forename: James
authors.initials: J
authors.lastname: Macion
authors.forename: Susan L
authors.initials: SL
authors.lastname: Smalley