ERP waveforms were extracted by averaging across trials for each condition. In addition to the ERP waveforms, the ERP difference waveforms (a) between the target and standard condition, and (b) between the rare non-target and standard condition were also computed. Grand average ERP waveforms for each condition were produced by averaging the ERPs within each group. Grand average topographical maps were also computed to display the spatial distribution of P300 amplitudes. The computation of grand average ERPs and topographical maps, and the extraction of amplitudes and latencies of the P300 components described below, were performed on both the ERP and the ERP difference waveforms.
