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Published in: Alzheimer's Research & Therapy 1/2018

Open Access 01-12-2018 | Research

The left frontal cortex supports reserve in aging by enhancing functional network efficiency

Authors: Nicolai Franzmeier, Julia Hartmann, Alexander N. W. Taylor, Miguel Á. Araque-Caballero, Lee Simon-Vermot, Lana Kambeitz-Ilankovic, Katharina Bürger, Cihan Catak, Daniel Janowitz, Claudia Müller, Birgit Ertl-Wagner, Robert Stahl, Martin Dichgans, Marco Duering, Michael Ewers

Published in: Alzheimer's Research & Therapy | Issue 1/2018

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Abstract

Background

Recent evidence derived from functional magnetic resonance imaging (fMRI) studies suggests that functional hubs (i.e., highly connected brain regions) are important for mental health. We found recently that global connectivity of a hub in the left frontal cortex (LFC connectivity) is associated with relatively preserved memory abilities and higher levels of protective factors (education, IQ) in normal aging and Alzheimer’s disease. These results suggest that LFC connectivity supports reserve capacity, alleviating memory decline. An open question, however, is why LFC connectivity is beneficial and supports memory function in the face of neurodegeneration. We hypothesized that higher LFC connectivity is associated with enhanced efficiency in connected major networks involved in episodic memory. We further hypothesized that higher LFC-related network efficiency predicts higher memory abilities.

Methods

We assessed fMRI during a face-name association learning task performed by 26 healthy, cognitively normal elderly participants. Using beta-series correlation analysis, we computed task-related LFC connectivity to key memory networks, including the default mode network (DMN) and dorsal attention network (DAN). Network efficiency within the DMN and DAN was estimated by the graph theoretical small-worldness statistic. We applied linear regression analyses to test the association between LFC connectivity with the DMN/DAN and small-worldness of these networks. Mediation analysis was applied to test LFC connectivity to the DMN and DAN as a mediator of the association between education and higher DMN and DAN small-worldness. Last, we tested network small-worldness as a predictor of memory performance.

Results

We found that higher LFC connectivity to the DMN and DAN during successful memory encoding and recognition was associated with higher small-worldness of those networks. Higher task-related LFC connectivity mediated the association between education and higher small-worldness in the DMN and DAN. Further, higher small-worldness of these networks predicted better performance in the memory task.

Conclusions

The present results suggest that higher education-related LFC connectivity to key memory networks during a memory task is associated with higher network efficiency and thus enhanced reserve of memory abilities in aging.
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Metadata
Title
The left frontal cortex supports reserve in aging by enhancing functional network efficiency
Authors
Nicolai Franzmeier
Julia Hartmann
Alexander N. W. Taylor
Miguel Á. Araque-Caballero
Lee Simon-Vermot
Lana Kambeitz-Ilankovic
Katharina Bürger
Cihan Catak
Daniel Janowitz
Claudia Müller
Birgit Ertl-Wagner
Robert Stahl
Martin Dichgans
Marco Duering
Michael Ewers
Publication date
01-12-2018
Publisher
BioMed Central
Published in
Alzheimer's Research & Therapy / Issue 1/2018
Electronic ISSN: 1758-9193
DOI
https://doi.org/10.1186/s13195-018-0358-y

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