A Signature of Passivity? An Explorative Study of the N3 Event-Related Potential Component in Passive Oddball Tasks

Many passive oddball experiments show a negative deflection N3 peaking between 400 and 500 ms, but this wave has never been analyzed properly. We conducted five passive oddball experiments, in which the number of deviants (i.e., one or two), their alleged meaning and their distinctiveness varied. Mastoid- or common-referenced waveforms showed a fronto-central N3 in all experiments. The data were CSD (Current Source Density) transformed and underwent a Principal Component Analysis (PCA). The PCA revealed N3 containing two subcomponents with very stable peak latencies of about 415 and 455 ms, respectively. Both topography of the subcomponents and their variation with experimental conditions were very similar but different from other negative ERP components N1 and N2. The two N3 subcomponents were maximally negative over midfrontal areas but positive over the parietal and particularly over the posterior temporal cortex. Both frontal negativity and posterior positivity exhibited clear oddball effects, i.e., they were larger to deviants than to standards. Positive components P3a and P3b were also analyzed, which replicated the previously known effects. In the Discussion, we speculate about possible meaning of N3; on this basis, specific hypotheses are formulated and further studies are suggested to test these hypotheses.