Multiple dipole analysis at visual event-related potentials during oddballparadigm with silent counting

In order to cope with the non-uniqueness of multiple equivalent current dip ole source (ECD) solutions, a priori knowledge about P300 generators of vis ual event-related potentials (ERPs) during an oddball paradigm with silent counting task was incorporated into the multiple ECD localization method. F our-ECD solutions for the target P300 were selected which had the left fron tal ECD. The rest of the ECDs were localized to the inferior parietal lobul e, the hippocampal formation and subcortical region. By comparing the prese nt results with those on the visual ERDs with button-pressing task, the P30 0 dipoles common to both the tasks were located at the frontal cortices, th e hippocampal formation and the thalamus, suggesting that these structures are the main P300 generators.