Semantic overlap protects from interference by restoring encoding mechanisms

Abstract

Overlap between experiences can have both facilitative and detrimental effects for memory. Our aim was to establish whether overlap along one dimension (e.g. contextual, semantic, temporal) can counteract overlap-driven interference along another dimension. We hypothesized that semantic overlap facilitates episodic memory formation by modulating encoding mechanisms. We recorded scalp electroencephalography (EEG) while human participants performed a free recall task. Half of the items from late in each study list semantically overlapped with an item presented earlier in the list. We find that semantic overlap selectively improves memory and influences the neural signals engaged during the study of late list items. Relative to other recalled items, late list items that are later recalled consecutively with semantically overlapping items elicited increased high frequency activity and decreased low frequency activity, a hallmark of successful encoding. Our findings demonstrate that semantic overlap can protect from interference due to temporal overlap by modulating encoding mechanisms. Statement of RelevancExperiences can overlap along different dimensions, including contextual, semantic, and tempo-ral. We tested the hypothesis that semantic overlap - shared meaning between experiences - may protect from interference due to temporal overlap, when experiences occur close together in time. Although evidence suggests that attention and/or encoding resources diminish across a series of study items presented in close temporal proximity, we find that semantic overlap can enable recovery of these encoding resources. Specifically, items that would typically be forgotten due to interference are better remembered and recruit distinct neural mechanisms when they share meaning with an earlier study item. These findings indicate that encoding mechanisms can be modulated by the degree of semantic overlap between two experiences. More broadly, our results suggest that experiences do not exist in isolation, rather that a prior experience can directly influence the neural mechanisms recruited to process a current experience.