A componential analysis of the ERP elicited by novel events using a dense electrode array.

In this study, we examined the relationship between the novelty P3 and the P300 components of the brain event-related potential (ERP). Fifteen subjects responded manually to the rare stimuli embedded either in a classical auditory oddball series or in a series in which "novel" stimuli were inserted. The electroencephalogram (EEG) was recorded with a dense array of 129 electrodes. The data were analyzed by using spatial Principal Components Analysis (PCA) to identify a set of orthogonal scalp distributions, "virtual electrodes" that account for the spatial variance. The data were then expressed as ERPs measured at each of the virtual electrodes. These ERPs were analyzed using temporal PCA, yielding a set of "virtual epochs." Most of the temporal variance of the rare events was associated with a virtual electrode with a posterior topography, that is, with a classical P300, which was active during the virtual epoch associated with the P300. The novel stimuli were found to elicit both a classical P300 and a component focused on a virtual electrode with a frontal topography. We propose that the term Novelty P3 should be restricted to this frontal component.