title: Electroencephalogram theta/beta ratio and arousal in attention-deficit/hyperactivity disorder: evidence of independent processes.
abstract: BACKGROUND
  For nearly 20 years, the theta/beta power ratio in the electroencephalogram (EEG) has been used within the attention-deficit/hyperactivity disorder (ADHD) literature as a marker of central nervous system (CNS) arousal, underpinning current models of the disorder. However, this usage has not been validated. We aimed to directly test the theta/beta ratio as a marker of arousal within this population.
  
  
  METHODS
  Resting state EEG activity was investigated as a function of CNS arousal in two age-matched groups of boys (each n = 30), with and without ADHD. Arousal was defined in terms of skin conductance level (SCL), which has a long history as a measure of CNS arousal.
  
  
  RESULTS
  Relative theta power and the theta/beta ratio were elevated, and SCL and relative alpha and beta power were reduced, in the ADHD group compared with control subjects. In both groups, mean alpha level correlated negatively with SCL. There was no significant correlation between the theta/beta ratio and SCL.
  
  
  CONCLUSIONS
  These data contradict the supposed linkage between the theta/beta ratio and arousal in ADHD, confirming previous results from normal children. They suggest the need for reevaluation of current models of the disorder and reconceptualization of existing EEG data from both normal and atypical populations.
authors.affiliation: Brain & Behaviour Research Institute and School of Psychology, University of Wollongong, 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: Stuart J
authors.initials: SJ
authors.lastname: Johnstone
authors.forename: Rory
authors.initials: R
authors.lastname: McCarthy
authors.forename: Mark
authors.initials: M
authors.lastname: Selikowitz
mesh_terms: D001143:Arousal / Q000502:physiology*; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology*; D001611:Beta Rhythm / Q000523:psychology*; D016022:Case-Control Studies; D002648:Child; D005712:Galvanic Skin Response / Q000502:physiology; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D013826:Theta Rhythm / Q000523:psychology*