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Electrophysiological Signals of Familiarity and Recency in the Infant Brain


should be sent to Kelly A. Snyder, Department of Psychology, University of Denver, 2155 S. Race St., Denver, CO 80208. E-mail:;


Electrophysiological work in nonhuman primates has established the existence of multiple types of signals in the temporal lobe that contribute to recognition memory, including information regarding a stimulus’s relative novelty, familiarity, and recency of occurrence. We used high-density event-related potentials (ERPs) to examine whether young infants represent these distinct types of information about previously experienced items. Twenty-four different highly familiar and initially novel items were each repeated exactly once either immediately (Experiment 1), or following one intervening item (Experiment 2). A late slow wave (LSW) component of the ERP exhibited neural responses consistent with recency signals over right-central leads, but only when there were no intervening stimuli between repetitions. The LSW also exhibited responses consistent with familiarity signals over anterior-temporal leads, but only when there were intervening stimuli between repetitions. A mid-latency negative component (i.e., the Nc) also distinguished familiar from novel items, but did not exhibit a pattern of responding consistent with familiarity signals. These findings suggest that infants encode information about a variety of objects from their natural environments into long-term memory, and can discriminate between familiar and unfamiliar items, and between recently seen and new items, very quickly (within 1 sec). They also suggest that infants represent information about not only whether a stimulus is familiar or unfamiliar but also whether it has been seen recently.