A review of electrophysiology in attention-deficit/hyperactivity disorder: II. Event-related potentials.

OBJECTIVE: This article reviews the event-related potential (ERP) literature in relation to attention-deficit/hyperactivity disorder (AD/HD).
METHODS: ERP studies exploring various aspects of brain functioning in AD/HD are reviewed, ranging from early preparatory processes to a focus on the auditory and visual attention systems, and the frontal inhibition system. Implications of these data for future research and development in AD/HD are considered.
RESULTS: A complex range of ERP deficits has been associated with the disorder. Differences have been reported in preparatory responses, such as the contingent negative variation. In the auditory modality, AD/HD-related differences are apparent in all components from the auditory brain-stem response to the late slow wave. The most robust of these is the reduced posterior P3 in the auditory oddball task. There are fewer studies of the visual attention system, but similar differences are reported in a range of components. Results suggesting an inhibitory processing deficit have been reported, with recent studies of the frontal inhibitory system indicating problems of inhibitory regulation.
CONCLUSIONS: The research to date has identified a substantial number of ERP correlates of AD/HD. Together with the robust AD/HD differences apparent in the EEG literature, these data offer potential to improve our understanding of the specific brain dysfunction(s) which result in the disorder. Increased focus on the temporal locus of the information processing deficit(s) underlying the observed range of ERP differences is recommended. Further work in this field may benefit from a broader conceptual approach, integrating EEG and ERP measures of brain function.