Poster Session E, Monday, March 25, 2:30 – 4:30 pm, Pacific Concourse
How memory reinstatement changes over time
Camille Gasser1, Alexa Tompary2, Lila Davachi1; 1Columbia University, 2University of Pennsylvania
Adapting to our environment relies on our capacity to form and retrieve lasting memories. Understanding how memories strengthen and transform over time and through consolidation processes is critical to understanding how these memories might guide behavior. For example, successful retrieval has been associated with stronger reinstatement of encoding activity patterns. Specifically, enhanced representational similarity between encoding and retrieval brain activity patterns (called encoding-retrieval similarity, or ERS) has been shown during successful retrieval in regions including sensory cortex, posterior medial cortex (PMC), angular gyrus, and hippocampus. The current research asks how the location and strength of reinstatement changes over time, potentially as a result of post-encoding consolidation processes. In a multi-day fMRI study, participants encoded a series of object-scene pairs. They were asked to retrieve half of these associations during an immediate memory test, and the remaining half during a delayed memory test one week later. We found that category-selective cortical regions such as lateral occipital cortex and parahippocampal place area showed evidence of episodic reinstatement only during immediate retrieval, and a searchlight analysis revealed a cluster in occipital cortex that exhibited significantly greater reinstatement during immediate relative to delayed retrieval. By contrast, right hippocampus showed significant reinstatement only after a week-long delay, and PMC exhibited reinstatement at both immediate and delayed retrieval. Future analyses will ask how these reinstatement effects are related to post-encoding connectivity between the hippocampus and neocortex, which likely contributes to the stabilization or transformation of mnemonic representations over time.
Topic Area: LONG-TERM MEMORY: Episodic