Another issue is that the P3 potential is not a unitary phenomenon, but consists of multiple subcomponents associated with different cognitive operations and neural generators (Kayser and Tenke, 2006a; Polich, 2007). P3 is typically measured in a two-stimulus oddball task, in which the subject responds to an infrequent target stimulus in a background of a frequent standard stimulus. The most commonly studied subcomponent observed in this task is the classical P3b potential to target stimuli, which has a parietal maximum scalp distribution and a peak latency ranging from 300–500 ms. The P3b component is often preceded by a component with a more frontocentral topography, i.e., P3a. Although this frontal aspect of P3 can be observed to target stimuli during an oddball task, it is most prominent to nontarget distracter stimuli that are interspersed along with the target and standard stimuli in a 3-stimulus oddball task (Polich and Criado, 2006). Novel distracter stimuli (e.g., environmental sounds) elicit a short latency “novelty P3” with a frontocentral distribution, which is indistinguishable from the P3a potential (Spencer et al., 1999; Simons et al., 2001).
