APA Dictionary of Psychology

a specific pattern of electrical activity produced in a particular part of the nervous system, especially the brain, in response to external stimulation, such as a flash of light or a brief tone. Different modalities and types of stimuli produce different types of sensory potentials, and these are labeled according to their electrical polarity (positive- or negative-going) and timing (by serial order or in milliseconds). Although the terms are sometimes used synonymously, EPs are distinct from event-related potentials, which are associated with higher level cognitive processes. Also called evoked response (ER).