Multiple generators in the auditory automatic discrimination process in humans.

To reveal the spatiotemporal characteristics of the auditory automatic discrimination process, mismatch negativity (MMN) generators were assessed with a high-resolution EEG system (128ch) and scalp current density (SCD) analysis. Ten normal volunteers participated in the study. Event-related potentials were recorded during a selective attention task. Sequential SCD mappings revealed that a current sink/source combination in the left temporal regions and a current sink in the right frontotemporal regions appeared around 200 msec irrespective of the ear of stimulation. Moreover, a parietal sink/source combination was demonstrated on the right hemisphere around 240 ms irrespective of the ear of stimulation. These findings demonstrate that the auditory automatic change detection process is, both spatially and temporally, a multiple-generated system.