Mnemonic but not contextual feedback signals defy dedifferentiation in the aging early visual cortex

Ehrlich, I., Ortiz-Tudela, J., Tan, Y. Y., Muckli, L. and Shing, Y. L. (2024) Mnemonic but not contextual feedback signals defy dedifferentiation in the aging early visual cortex. Journal of Neuroscience, 44(16), e0607232023. (doi: 10.1523/JNEUROSCI.0607-23.2023) (PMID:38395614) (PMCID:PMC11026335)

Abstract

Perception is an intricate interplay between feedforward visual input and internally generated feedback signals that comprise concurrent contextual and time-distant mnemonic (episodic and semantic) information. Yet, an unresolved question is how the composition of feedback signals changes across the lifespan and to what extent feedback signals undergo age-related dedifferentiation, i.e., a decline in neural specificity. Previous research on this topic has focused on feedforward perceptual representation and episodic memory reinstatement, suggesting reduced fidelity of neural representations at the item and category levels. In this fMRI study, we combined an occlusion paradigm that filters feedforward input to the visual cortex and multivariate analysis techniques to investigate the information content in cortical feedback, focusing on age-related differences in its composition. We further asked to what extent differentiation in feedback signals (in the occluded region) is correlated to differentiation in feedforward signals. Comparing younger (18 - 30 years) and older female and male adults (65 -75 years), we found that contextual but not mnemonic feedback was prone to age-related dedifferentiation. Semantic feedback signals were even better differentiated in older adults, highlighting the growing importance of generalized knowledge across age. We also found that differentiation in feedforward signals was correlated with differentiation in episodic but not semantic feedback signals. Our results provide evidence for age-related adjustments in the composition of feedback signals and underscore the importance of examining dedifferentiation in aging for both feedforward and feedback processing.

• Item Type: Articles
• Additional Information: This work was funded by a European Research Council Starting Grant (ERC-2018-StG-PIVOTAL-758898). The work of YLS is also supported by the German Research Foundation (Project ID 327654276, SFB 1315, “Mechanisms and Disturbances in Memory Consolidation: From Synapses to Systems”) and the Hessisches Ministerium für Wissenschaft und Kunst (HMWK; project “The Adaptive Mind”). The work of JO is funded by the Volkswagen Stiftung (project: 9B326). LM has received funding for this project from the Biotechnology and Biological Science Research Council (BBSRC) BB/V010956/1 (‘Layer-specific cortical feedback dynamics’).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Ortiz-Tudela, Dr Javier and Muckli, Professor Lars
• Authors: Ehrlich, I., Ortiz-Tudela, J., Tan, Y. Y., Muckli, L., and Shing, Y. L.
• College/School: College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
• Journal Name: Journal of Neuroscience
• Publisher: Society for Neuroscience
• ISSN: 0270-6474
• ISSN (Online): 1529-2401
• Published Online: 23 February 2024
• Copyright Holders: Copyright © 2024 Ehrlich et al.
• First Published: First published in Journal of Neuroscience 44(16): e0607232023
• Publisher Policy: Reproduced under a Creative Commons licence

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
311400		Layer-specific cortical feedback dynamics - Human Ultra-High Resolution functional Brain Imaging for Predictive Brain Functions	Lars Muckli	Biotechnology and Biological Sciences Research Council (BBSRC)	BB/V010956/1	SPN - Centre for Cognitive Neuroimaging (CCNi)