Excess beta activity in the EEG of children with attention-deficit/hyperactivity disorder: A disorder of arousal?
Past research has reported that a small proportion of children with attention-deficit/hyperactivity disorder (AD/HD) have excess beta activity in their EEG, rather than the excess theta typical of the syndrome. This atypical group has been tentatively labeled as hyperaroused. The aim of this study was to determine whether these children have a hyperaroused central nervous system. Participants included 104 boys aged 8 to 13 years old, with a diagnosis of either the Combined or Inattentive type of AD/HD (67 combined type), and 67 age-matched male controls. Ten and a half minutes of EEG and skin conductance (SCL) were simultaneously recorded during an eyes-closed resting condition. The EEG was Fourier transformed and estimates of total power, and relative power in the delta, theta, alpha, and beta bands, and the theta/beta ratio, were calculated. AD/HD patients were divided into an excess beta group and a typical excess theta group. Relative to controls, the typical excess theta group had significantly increased frontal total power, theta and theta/beta ratio, with reduced alpha and beta across the scalp. The excess beta group had significantly reduced posterior total power, increased centro-posterior delta, globally reduced alpha, globally increased beta activity, and globally reduced theta/beta ratio. Both AD/HD groups had significantly reduced SCL compared to the control group, but the two groups did not differ from each other on SCL. These results indicate that AD/HD children with excess beta activity are not hyperaroused, and confirm that the theta/beta ratio is not associated with arousal. This is the first study of arousal measures in AD/HD children with excess beta activity, and has implications for existing models of AD/HD.