Components in the P300: Don't forget the Novelty P3!

This study investigated stimulus-response patterns of temporal principal components analysis (PCA)-derived event-related potential (ERP) components in a classical auditory habituation paradigm with long interstimulus intervals. The skin conductance response (SCR) was included as the "gold standard" model of the Orienting Reflex. Thirty participants were presented with a single series of 10 identical 60 dB tones, followed by a change trial at a different frequency. Single-trial, electrooculography-corrected ERPs were submitted to temporal PCA. The main focus was on the components expected in the P300/Late Positive Complex (LPC), and their electromagnetic tomography-derived cortical sources. Nine components were identified between 90 and 470 ms poststimulus (in temporal order): three N1 subcomponents, P2, four LPC components, and a negative Slow Wave (SW). The expected order of P3a, P3b, Novelty P3 (nP3), and positive Slow Wave (+SW) in the LPC was confirmed. SCR demonstrated strong exponential decay and recovery. P3b and nP3 each showed exponential decrement over trials, but only nP3 showed recovery at the change trial. Novelty effects failed to reach significance for the other LPC components, and were not apparent in non-LPC components. Frontal lobe activity in Brodmann areas 6, 8, and 9 was common to P3a, P3b, nP3, and +SW, consistent with the functional integration of these components in the LPC. Individual components had specific sources, although some sources overlapped between components or were reactivated later in the LPC. These data provide a fresh perspective on the components of the LPC and their cortical sources, and offer a processing model for the P300 in a habituation task, potentially generalizable to other paradigms.