title: EEG coherence in attention-deficit/hyperactivity disorder: a comparative study of two DSM-IV types.
abstract: OBJECTIVE
  This study investigated differences in intrahemispheric and interhemispheric electroencephalographic (EEG) coherences between attention-deficit/hyperactivity disorder (ADHD) and control children, and between children with the Combined (ADHDcom) and Inattentive (ADHDin) types of ADHD.
  
  
  METHODS
  Three age- and sex-matched groups of 40 children, aged 8-12 years, diagnosed with ADHDcom, ADHDin, and normal control children, participated in this study. EEG was recorded from 21 sites during an eyes-closed resting condition and Fourier transformed. Wave-shape coherence was calculated for 8 intrahemispheric electrode pairs (4 in each hemisphere), and 8 interhemispheric electrode pairs, within each of the delta, theta, alpha and beta bands.
  
  
  RESULTS
  At shorter inter-electrode distances, ADHD children had elevated intrahemispheric coherences in the theta band and reduced lateral differences in the theta and alpha bands. At longer inter-electrode distances, ADHD children had lower intrahemispheric alpha coherences than controls. Frontally, ADHD children had interhemispheric coherences elevated in the delta and theta bands, and reduced in the alpha band. An alpha coherence reduction in temporal regions, and a theta coherence enhancement in central/parietal/occipital regions, were also apparent. ADHDcom had greater intrahemispheric theta and beta coherences than ADHDin. Frontally, ADHDcom had higher levels of interhemispheric coherences than ADHDin for the delta and theta bands. In central/parietal/occipital regions, beta coherences were elevated in ADHDcom.
  
  
  CONCLUSIONS
  EEG coherences suggest reduced cortical differentiation and specialisation in ADHD, particularly in cortico-cortical circuits involving theta activity. Generally, ADHDcom children displayed greater anomalies than ADHDin children.
authors.affiliation: Brain & Behaviour Research Institute and Department of Psychology, University of Wollongong, 2522, Wollongong, Australia. robert_barry@uow.edu.au
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Barry
authors.forename: Adam R
authors.initials: AR
authors.lastname: Clarke
authors.forename: Rory
authors.initials: R
authors.lastname: McCarthy
authors.forename: Mark
authors.initials: M
authors.lastname: Selikowitz
mesh_terms: D000704:Analysis of Variance; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology*; D002648:Child; D004569:Electroencephalography / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D006801:Humans; D007361:Intelligence Tests / Q000706:statistics & numerical data; D008297:Male