A shared brain state for episodic and semantic retrieval

Abstract

It is critical to identify which factors induce specific brain states as these large-scale patterns of coordinated neural activity drive downstream processing and behavior. The retrieval state, a brain state engaged when attempting to retrieve the past, is thought to specifically support episodic memory, remembering experiences within a spatiotemporal context, as opposed to semantic memory, remembering general knowledge. However, we hypothesize that the retrieval state reflects internal attention engaged to access stored episodic and semantic information. To test these alternatives, we recorded scalp electroencephalography while male and female human participants made episodic, semantic, or perceptual judgments, and applied an independently validated mnemonic state classifier to measure retrieval state engagement. We found that retrieval state engagement was greater for both episodic and semantic judgments compared to perceptual judgments. These findings suggest that the retrieval state reflects a domain-general internal attention process that supports not just episodic memory, but internally directed cognition. Significance Statement Understanding brain states, whole-brain activity/connectivity patterns, is critical as brain states influence downstream processing and behavior. The retrieval state is a multivariate brain state that influences behavior and is thought to be specific to episodic remembering, accessing stored information about one’s past experiences. Here we use a machine learning decoding approach to show that the retrieval state is also recruited to support semantic remembering, accessing stored general knowledge and facts. These findings suggest that the retrieval state reflects a domain-general internal attention state.