Engram stability and maturation during systems consolidation

Ron Refaeli, Tirzah Kreisel, Maya Groysman, Adar Adamsky, Inbal Goshen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Remote memories play an important role in how we perceive the world, and they are rooted throughout the brain in “engrams”: ensembles of cells that are formed during acquisition. Upon their reactivation, a specific memory can be recalled.1,2,3,4,5,6,7,8,9,10,11,12 Many studies have focused on the ensembles in CA1 of the hippocampus and the anterior cingulate cortex (ACC). However, the evolution of these components during systems’ consolidation has not yet been comprehensively addressed.13,14,15,16 By applying transgenic approaches for ensemble identification, CLARITY, retro-AAV, and pseudo-rabies virus for circuit mapping, and chemogenetics for functional interrogation, we addressed the dynamics of recent and remote CA1 ensembles. We expected both stability (as they represent the same memory) and maturation (over time). Indeed, we found that CA1 engrams remain stable between recent and remote recalls, and the inhibition of engrams for recent recall during remote recall functionally impairs memory. We also found that new cells in the remote recall engram in the CA1 are not added randomly during maturation but differ according to their connections. First, we show in two ways that the anterograde CA1 → ACC engram cell projection grows larger. Finally, in the retrograde projections, the ACC reduces input to CA1 engram cells, whereas input from the entorhinal cortex and paraventricular nucleus of the thalamus increases. Our results shine fresh light on systems’ consolidation by providing a deeper understanding of engram stability and maturation in the transition from recent to remote memory.

Original languageAmerican English
Pages (from-to)3942-3950.e3
JournalCurrent Biology
Issue number18
StatePublished - 25 Sep 2023

Bibliographical note

Publisher Copyright:
© 2023 The Authors


  • CA1
  • anterior cingulate cortex
  • engram
  • pseudo-rabies
  • recent memory
  • remote memory
  • retro-AAV


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