title: Functional disconnection of frontal cortex and visual cortex in attention-deficit/hyperactivity disorder.
abstract: BACKGROUND
  Current pathophysiologic models of attention-deficit/hyperactivity disorder (ADHD) suggest that impaired functional connectivity within brain attention networks may contribute to the disorder. In this electroencephalographic (EEG) study, we analyzed cross-frequency amplitude correlations to investigate differences in cue-induced functional connectivity in typically developing children and children with ADHD.
  
  
  METHODS
  Electroencephalographic activity was recorded in 25 children aged 8 to 12 years (14 with ADHD) while they performed a cross-modal attention task in which cues signaled the most likely (.75 probability) modality of an upcoming target. The power spectra of the EEG in the theta (3-5 Hz) and alpha (8-12 Hz) bands were calculated for the 1-sec interval after the cue and before the target while subjects prepared to discriminate the expected target.
  
  
  RESULTS
  Both groups showed behavioral benefits of the predictive attentional cues, being faster and more accurate for validly cued targets (e.g., visual target preceded by a cue predicting a visual target) than to invalidly cued targets (e.g., visual target preceded by a cue predicting an auditory target); in addition, independent of cue-target validity, typical children were faster to respond overall. In the typically developing children, the alpha activity was differentially modulated by the two cues and anticorrelated with midfrontal theta activity; these EEG correlates of attentional control were not observed in the children with ADHD.
  
  
  CONCLUSIONS
  Our findings provide neurophysiological evidence for a specific deficit in top-down attentional control in children with ADHD that is manifested as a functional disconnection between frontal and occipital cortex.
authors.affiliation: Center for Mind and Brain, University of California, Davis, Davis, California 95618, USA. amazaheri@ucdavis.edu
authors.forename: Ali
authors.initials: A
authors.lastname: Mazaheri
authors.forename: Sharon
authors.initials: S
authors.lastname: Coffey-Corina
authors.forename: George R
authors.initials: GR
authors.lastname: Mangun
authors.forename: Evelijne M
authors.initials: EM
authors.lastname: Bekker
authors.forename: Anne S
authors.initials: AS
authors.lastname: Berry
authors.forename: Blythe A
authors.initials: BA
authors.lastname: Corbett
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology*; D002648:Child; D004569:Electroencephalography; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology*; D006801:Humans; D008297:Male; D009415:Nerve Net / Q000503:physiopathology*; D014793:Visual Cortex / Q000503:physiopathology*