The P300 component of the event-related potential (ERP) was first identified by Sutton et al (1965). This component is a scalp positive wave that occurs approximately 300 ms after an informative stimulus occurs. The informative nature of a stimulus is defined by the experimental design in which the subject is typically instructed to attend to one stimulus (target) while ignoring another in the often used “oddball” paradigm. The frequency of the target stimulus presentation or the probability it will occur, along with the task relevance to the subject affects the amplitude of P300 component so that early studies concluded that P300 was thought to be an index of capacity to attend to and process stimulus information (Donchin, 1979; Pritchard, 1981). Currently, we know that amplitude is affected by the stimulus paradigms used, the age and gender of subjects, and host of other variables including genetic factors (Polich, 2007; Euser et al 2012; Iacono and Malone, 2011).
