The effects of methylphenidate (MPH) on the EEG during baseline and cognitive tasks were evaluated using spectral analysis in 23 boys, aged 9 to 11, with ADHD, and results were analyzed at the Departments of Psychology, State University of New York, Cortland, NY, and University of Tennessee, Knoxville, TN, and the Kennedy Krieger Institute, Baltimore, MD. Behavioral and performance measures improved with MPH, global effects on the cortical EEG were not observed, but regional changes in the EEG were induced by MPH under task-specific conditions. The findings support the hypothesis that MPH affects the brainstem and subcortical areas but not cortical function. The value of the EEG as a measure of MPH effectiveness is not supported by these studies. 
COMMENT. Earlier EEG studies in ADHD subjects, reviewed by the authors, have shown a failure to attenuate alpha activity during mental tasks, decreased beta activity, and increased delta and theta activity. Treatment with MPH may have a normalizing effect, with trends in reduced alpha, increased beta, and reduced overall amplitude. The present study shows EEG changes during MPH treatment, mainly regional and during reading, coding, and visual-motor tasks. Increased beta 1 and beta 2 activity in central and parietal regions of the left hemisphere during visual-motor tasks point toward a normalizing effect of MPH on the EEG. The EEG as a measure of MPH effects in ADHD requires further study.