Abstract
BackgroundMany passive oddball experiments show a sharp negative deflection N3 after P3b, 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.ResultsMastoid- 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, indicating a midfrontal sink and a posterior temporal source. An analysis of P3a and P3b components replicated previously known effects.ConclusionWe discuss the similarities and differences between the passive N3 and other components including the MMN, N1, late positive Slow Wave, and reorienting negativity. We also make general hypotheses about a possible functional meaning of N3; on this basis, specific hypotheses are formulated and further experiments are suggested to test these hypotheses.
Highlights
More than half a century has passed since we first learned that infrequent stimuli, presented among highly frequent ones, elicit in the EEG a slow late positive wave with a typical peak latency slightly longer than 300 ms (Sutton et al, 1965)
In the following text only sporadic statistical results are explained that are not resumed in the tables
N3, the main object of the present study, revealed in the PCA as entailing two principal components (PCs), PC2, and PC4, with peak latencies of 412 and 456 ms, respectively. Both PCs were negative at frontal sites and positive at Pz, resulting in a main effect of site
Summary
More than half a century has passed since we first learned that infrequent stimuli, presented among highly frequent ones, elicit in the EEG a slow late positive wave with a typical peak latency slightly longer than 300 ms (Sutton et al, 1965). Already the first systematic review on this effect is almost four decades old (Donchin, 1981). Later on, this late positivity of the event-related potential (ERP), called P300 or P3, was found to entail two distinct components, P3a and P3b (e.g., Courchesne et al, 1975). If subjects have to respond to rare stimuli, the factors of rarity (or probability) and taskrelevance are confounded. This fact underlay the idea to obtain the same effect without any active. Many passive oddball experiments show a sharp negative deflection N3 after P3b, 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
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