Grand average waveform and topographical map of mismatch negativity (MMN).

<p>MMN was derived by subtracting the ERP response to the standard from that to the deviant stimuli. The topographical maps were constructed at the peak latency of the MMN. (A) ERP waveforms at the Fz electrode for the rising deviant type (T2). (B) ERP waveforms at the Fz electrode for the falling deviant type (T4).