Neurophysiological Evidence for Rapid Semantic Integration via Fast Mapping

Theories of declarative memory consolidation hold that novel associative information is integrated into cortical semantic networks slowly and with hippocampal support. However, an encoding paradigm called fast mapping (FM) has been proposed to permit rapid cortical integration of novel item-label associations, particularly when the novel item shares substantial visual-semantic features with a simultaneously presented known concept. We tested whether associations encoded through FM immediately engage semantic memory networks, indexed by the N400 event-related potential. In contrast to behavioral semantic priming tasks, in which semantic relatedness and response congruency may be confounded, the present EEG study provides a more process-specific test of rapid semantic integration. Sixty participants encoded pairs of a novel item and an unfamiliar label under two conditions, differing with respect to the visual-semantic overlap between the novel item and a simultaneously presented known item. In a subsequent semantic priming task, the novel labels served as primes for semantically related versus unrelated targets. While behavioral results did not reveal a significant priming effect, EEG data indicated an N400 priming effect in the high-overlap FM condition, characterized by reduced N400 amplitudes for related compared to unrelated targets over a parietal electrode cluster. Crucially, the N400 effect was significantly larger after high-overlap FM than after low-overlap FM encoding, indicating that high feature overlap enhances rapid semantic integration already minutes after learning. These findings provide the first neurophysiological evidence that high-overlap FM enables rapid semantic integration.