A pilot study of the effects of methylphenidate on the vigilance-related EEG in hyperactivity

Seven hyperactive children underwent a reaction time (RT) test requiring prolonged (15 min) vigilance, once while receiving methylphenidate and once without medication. EEG samples taken immediately before each RT measurement were subjected to power-spectral analysis. Compared to the off-medication condition, methylphenidate reduced the RT whilst paradoxically increasing EEG alpha power relative to higher and lower frequencies in 5 out of the 7 children. On this medication, the RT increased during the course of the task, and the relative EEG alpha power increased compared to other frequencies. Off medication, RTs showed an even greater increase with prolonged vigilance, but the accompanying EEG changes were the reverse of those seen on medication. The altered EEG power spectrum on methylphenidate appears closer to that of a normal EEG, and may be related to the improvement in specific attention produced by this drug in hyperactivity.