Positive Emotion Enhances Memory by Promoting Memory Reinstatement across Repeated Learning

In daily life, we frequently encounter items within emotional contexts through repeated exposure. However, it remains unclear how emotion influences the memory of items learned across multiple repetitions and how neural representations during repeated learning are associated with subsequent memory performance. In the current study, participants learned meaningless squiggles, each followed by an emotional image (positive, neutral, or negative), with each squiggle-image pair presented three times during encoding. After a 24 h delay, a recognition memory test for the squiggles was performed. The results indicated that behaviorally squiggles were more accurately retrieved in the positive condition compared with the negative condition. An old/new ERP effect was observed between 400 and 1,200 ms at the midparietal cluster, specific to the positive condition, and correlated with memory performance. Notably, greater EEG representational similarity of neural patterns across repeated learning was observed for subsequently remembered items compared with forgotten items in the positive condition, specifically at the right frontal region between 380 and 600 ms. These findings suggest that positive emotion enhances memory of neutral items across repeated learning through neural representational reinstatement, offering insights into how emotional differences in episodic memory retrieval are linked to neural patterns established during repeated learning.