An assessment of the effects of methylphenidate on electrophysiological, behavioral, and performance measures

This study provides an evaluation of both psychophysiological and behavioral effects of methylphenidate in a homogeneous group of 23 ADHD (with hyperactivity) boys between the ages of 9 and 11 years. Previous research has demonstrated that ADHD (without hyperactivity) children show increased theta activity and decreased beta activity when compared to normal controls (Mann, et. al., 1992). This suggests that these brain rhythms might be affected by MPH administration, which is known to affect ADHD symptomatology (DuPaul and Barkley, 1990). The effects of methylphenidate on electrophysiological indices of brain activation including both referential EEG spectral analysis and cortical event related potentials were investigated. Measurements were taken during baseline conditions as well as during cognitive tasks. In addition, both subjective (rating scales) and objective (continuous performance test) measures were administered and analyzed in conjunction with the physiological data. Results indicate that MPH does not appear to have any robust effects on the cortical EEG. Regional changes were induced in the EEG with MPH administration only under certain task-specific conditions. Additionally, the N1 component of the visual evoked response was not significantly affected by MPH administration. Finally, correlations between EEG, behavioral, and performance data revealed no consistent relationships. While behavioral and performance measures showed large improvements with MPH, it appears that MPH had little effect on the cerebral cortex as measured by the cortical EEG.