Retrieval processes reflect the representational format of memories acquired through fast mapping: ERP evidence for conceptual fluency-based familiarity.

Traditional theories of declarative memory assign the hippocampus a central role in binding novel associations, with neocortical representations emerging only gradually through systems consolidation. However, recent evidence suggests that novel picture-label associations can be rapidly acquired through fast mapping (FM), an incidental learning paradigm through which a novel label is inferred as the name of an unknown object through rejection of a known distractor object. Recent evidence suggests that FM may capitalize on perirhinal cortex (PrC) processes, especially under conditions of high feature overlap (FMHO) between the known and the unknown object, where the task requires fine-grained PrC-mediated object discrimination and binding. These processes potentially support the unitization of the picture-label associations, by which item-like representations are created that can subsequently be retrieved by conceptual fluency-based familiarity rather than hippocampal recollection. The present event-related potential study investigated retrieval processes after FMHO compared to explicit encoding (EE). Participants judged labels as old or new and subsequently selected the corresponding picture in a forced-choice test. Behaviorally, EE yielded superior associative recognition performance, consistent with assumptions about intentional memorization. Electrophysiologically, FMHO was associated with an enhanced N400 old/new effect as compared to EE, indicating familiarity-based retrieval driven by conceptual fluency. These findings highlight that the representational format established during FMHO critically impacts the processes involved at retrieval. Specifically, FMHO promotes retrieval dynamics presumably rooted in PrC-mediated fluency.