Visual event related potentials after methylphenidate and sodium valproate in children with attention deficit hyperactivity disorder.

We divided a group of Attention Deficit Hyperactivity Disorder (ADHD) boys into two groups determined by the results of EEG and visual ERP tests--those who had excessive EEG background slowing, EEG epileptiform activity or abnormally high amplitude ERP waves (the "E-ADD" group), and those with normal EEG and ERP (the "ADD" group). The subjects of each group were then given either a dose of methylphenidate (Ritalin, MPH), sodium valproate (Depakene, VPA) or placebo, and repeated visual ERPs one hour later. Following both medications there was a significant suppression of the amplitude of the N3, the "slow negative" wave of the ERP, in the E-ADD group but not in the ADD group. The effect of VPA and MPH in ADHD children may be related to the electrophysiological (EEG, ERP) background. Both medications may have a similar effect on arousal processes in ADHD.