Spatiotemporal dynamics of the auditory novelty-P3 event-related brain potential.

The spatiotemporal dynamics of the cerebral network involved in novelty processing was studied by means of scalp current density (SCD) analysis of the novelty P3 (nP3) event-related brain potential (ERP). ERPs were recorded from 30 scalp electrodes at the occurrence of novel unpredictable environmental sounds during the performance of a visual discrimination task. Increased SCD was observed at left frontotemporal (FT3), bilateral temporoparietal (TP3 and TP4) and prefrontal locations (F8-F4 and F7-F3), suggesting novelty-P3 generators located in the left auditory cortex, and bilaterally in temporoparietal and prefrontal association regions. Additional increased SCD was found at a central location (Cz) and at superior parietal locations (P3-Pz-P4). The SCD of the nP3 was therefore generated at three successive, partially overlapping, stages of neuroelectric activation. At the central location, SCD started to be significant before the onset of the nP3 waveform, contributing solely to its early phase. At temporoparietal and left frontotemporal locations, nP3 electrophysiological activity was characterized by sustained current density, starting at about 210 ms and continuing during the full latency range of the response, including its early and late phases. At its late phase, the nP3 was characterized by sharp phasic current density at prefrontal and superior parietal locations, starting at about 290 ms and vanishing at around 385 ms. Taken together, these results provide the first evidence of the cerebral spatio-temporal dynamics underlying novelty processing.