The P300 is an event-related potential that usually appears 300 ms after the recognition of a specific stimulus in a series of stimuli that are unlike with the presented stimulus. The P300 is often referred to as the “oddball stimulus.” Its spatial signature is a spherically symmetric distribution with the vertex (electrode position Cz) as its center, which dominates at parietal electrode sites and is typically a positive waveform of a few to 100 mV.
The occurrence of the P300 seems to be a marker for attention to a stimulus of interest that replaces the “boredom” of a series of stimuli that do not have the specific qualities that are to be responded to. It is understood to indicate that the subject is consciously identifying and categorizing the stimulus and updating working memory with the new information. The P300 only peaks in the vicinity of 300 ms for very simple decisions. More difficult and complex categorizing decisions...
References and Readings
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