After the attenuation of BCG, imaging and ocular artifacts (Fig. 1), single-subject EEG data collected during simultaneous fMRI scanning were analyzed. ERP scalp topography and scalp maps at P300 latency showed a major contribution of the P300 component over the centro-parietal region, with latency in the 300–400ms range (Fig. 2). Early N1 and P1 components could also be observed in the ERP, although they were weaker than the P300 component. The analysis of the ERP SNR across subjects, in line with the spatial distribution of the P300 component, showed a bilateral pattern, more prominent at P3 and P4 electrodes (Supplementary Fig. 2). Electrophysiological measures of the ongoing cerebral activity related to target detection were obtained by single-trial analysis of the P300 responses (Fig. 3 and Supplementary Fig. 3). Raster plots of time-locked responses at electrode Pz were generated for all trials together, and for rare and frequent events separately (Figs. 3a and b, respectively). The latter clearly revealed differences among the two groups in terms of event-related electric activity at the latency of about 350 ms, which corresponded to the
