Event-related potentials (ERPs) represent EEG changes in response to a discrete event relative to the baseline activity preceding that event. The ERP is averaged across trials and represents changes in the electric potential that are phase-locked to the even onset (evoked activity), and do not include activity that may be systematically related to the stimulus but does not show exact phase alignment with the stimulus. Historically, two types of evoked activity are distinguished: evoked potentials (EP) elicited by sensory stimuli and varying as a function of stimulus characteristics and event-related, or “endogenous” potentials that vary as a function of the subjective meaning of the stimulus, rather than its sensory characteristics.
