Semantic predictability and semantic relevance through different neural mechanisms to improve memory performance

Previous studies have shown that semantic predictability and semantic relevance enhance the semantic activation of target words and improve memory performance. However, it is unclear whether semantic predictability and semantic relevance affect memory performance through the same neural mechanisms. The present study examined how semantic processing of semantic predictability and semantic relevance during encoding affects episodic memory retrieval. In our experiments (Experiment 1: item recognition; Experiment 2: associative recognition), we compared behavioral and EEG indicators across true (predictable), invalid (unpredictable but semantically relevant), and anomalous (unpredictable and semantically irrelevant) conditions. In both experiments, memory performance was best in the true condition. In Experiment 1, the old/new effect of FN400 was observed in the invalid condition, while the old/new effect of LPC was observed in the true condition. In Experiment 2, the old/new effects of FN400 and LPC were observed in the invalid condition. In the true condition, only the old/new effect of LPC was observed. These results suggest that semantic predictability and semantic relevance influence FN400 and LPC in different ways. These findings demonstrate that there are differences between semantic predictability and semantic relevance in retrieving information.