Aging alters the distribution, stability, and transcriptional signature of engram cells

While aging impairs memory precision, its effects on engram dynamics and gene expression remain poorly understood. Here, we used nuclear tagging and FOS-based activity mapping to track neurons activated during contextual fear memory encoding and recall in young and aged mice. Brain-wide quantification revealed age-dependent differences in engram activation, spatial distribution, and functional connectivity between memory-related brain regions.

To investigate the molecular basis of these changes, we combined nuclear sorting with single-nucleus RNA sequencing, and identified transcriptional signatures associated with memory recall across neuronal cell types further dissected through the comparison of first- and second-time responder neurons. In aged mice, recall-associated engrams showed reduced reactivation and coordination of activity-dependent transcription, particularly in the dentate gyrus, consistent with increased inhibitory engagement by somatostatin-expressing interneurons. These findings reveal age-related changes in the organization and molecular identity of memory traces, providing mechanistic insight into cognitive decline and potential targets for intervention.

We thank Jose Vicente Sanchez-Mut and Rafael Alcala-Vida for critical reading of the manuscript. We thank the personnel of the Mouse facility, and the Omics core services at the Instituto de Neurociencias for their assistance. Racovac for technical assistance.

Declaration of generative AI and AI-assisted technologies in the writing process: During the preparation of this work the authors used ChatGPT to revise English grammar and usage. After using this tool/service, the authors reviewed and edited the content as needed and take full responsibility for the content of the publication. M.F-R. was recipient of a FPU fellowship from the Spanish Ministry of Education.

J.P-L. is recipient of a CIAPOS contract given by Generalitat Valenciana and European Social Found. P.T-R. and M.A-N. are recipients of fellowships from Generalitat Valenciana. I.B-M. is recipient of a fellowship from the Spanish Ministry of Science and Innovation (MICINN).

A.B. research is supported by grants FCAIXA HR22-00394 from Fundación LaCaixa, PID2020-118169RB-I00 and PID2023-148442NB-I00 funded by MICIU/AEI/10.13039/501100011033 and ERDF/EU, and CIPROM/2023/15 from the Generalitat Valenciana. The Instituto de Neurociencias is a “Centre of Excellence Severo Ochoa” (CEX2021-001165-S funded by MICIU/AEI/10.13039/501100011033). Instituto de Neurociencias de Alicante (Universidad Miguel Hernández - Consejo Superior de Investigaciones Científicas), Alicante, Spain Miguel Fuentes-Ramos, Juan Paraíso-Luna, Patricia Torres-Raves, Isabel Bustos-Martínez, Marta Alaiz-Noya, Federico Miozzo, Jordi Fernández-Albert, Felix Leroy & Angel Barco Laboratory of Structural Plasticity, Institut du Cerveau et de la Moelle Epiniere, Hôpital Pitié-Salpêtrière, Paris, France The authors declare no competing interests.