title: Resting-state global functional connectivity as a biomarker of cognitive reserve in mild cognitive impairment.
abstract: Cognitive reserve (CR) shows protective effects in Alzheimer's disease (AD) and reduces the risk of dementia. Despite the clinical significance of CR, a clinically useful diagnostic biomarker of brain changes underlying CR in AD is not available yet. Our aim was to develop a fully-automated approach applied to fMRI to produce a biomarker associated with CR in subjects at increased risk of AD. We computed resting-state global functional connectivity (GFC), i.e. the average connectivity strength, for each voxel within the cognitive control network, which may sustain CR due to its central role in higher cognitive function. In a training sample including 43 mild cognitive impairment (MCI) subjects and 24 healthy controls (HC), we found that MCI subjects with high CR (> median of years of education, CR+) showed increased frequency of high GFC values compared to MCI-CR- and HC. A summary index capturing such a surplus frequency of high GFC was computed (called GFC reserve (GFC-R) index). GFC-R discriminated MCI-CR+ vs. MCI-CR-, with the area under the ROC = 0.84. Cross-validation in an independently recruited test sample of 23 MCI subjects showed that higher levels of the GFC-R index predicted higher years of education and an alternative questionnaire-based proxy of CR, controlled for memory performance, gray matter of the cognitive control network, white matter hyperintensities, age, and gender. In conclusion, the GFC-R index that captures GFC changes within the cognitive control network provides a biomarker candidate of functional brain changes of CR in patients at increased risk of AD.
authors.affiliation: Institut für Schlaganfall-und Demenzforschung (ISD), Ludwig-Maximilians-Universität LMU, Klinikum der Universität München, Feodor-Lynen Straße 17, 81377, Munich, Germany. nicolai.franzmeier@med.uni-muenchen.de.
authors.forename: N
authors.identifier: 0000-0001-9736-2283
authors.initials: N
authors.lastname: Franzmeier
authors.affiliation: Institut für Schlaganfall-und Demenzforschung (ISD), Ludwig-Maximilians-Universität LMU, Klinikum der Universität München, Feodor-Lynen Straße 17, 81377, Munich, Germany.
authors.forename: M Á Araque
authors.initials: MÁA
authors.lastname: Caballero
authors.affiliation: Institut für Schlaganfall-und Demenzforschung (ISD), Ludwig-Maximilians-Universität LMU, Klinikum der Universität München, Feodor-Lynen Straße 17, 81377, Munich, Germany.
authors.forename: A N W
authors.initials: ANW
authors.lastname: Taylor
authors.affiliation: Institut für Schlaganfall-und Demenzforschung (ISD), Ludwig-Maximilians-Universität LMU, Klinikum der Universität München, Feodor-Lynen Straße 17, 81377, Munich, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Simon-Vermot
authors.affiliation: Institut für Schlaganfall-und Demenzforschung (ISD), Ludwig-Maximilians-Universität LMU, Klinikum der Universität München, Feodor-Lynen Straße 17, 81377, Munich, Germany.|German Center for Neurodegenerative Diseases (DZNE, Munich), Feodor-Lynen Straße 17, 81377, Munich, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Buerger
authors.affiliation: Institute for Clinical Radiology, Klinikum der Universität München, Ludwig-Maximilian University, Marchioninistraße 15, 81377, Munich, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Ertl-Wagner
authors.affiliation: Institut für Schlaganfall-und Demenzforschung (ISD), Ludwig-Maximilians-Universität LMU, Klinikum der Universität München, Feodor-Lynen Straße 17, 81377, Munich, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Mueller
authors.affiliation: Institut für Schlaganfall-und Demenzforschung (ISD), Ludwig-Maximilians-Universität LMU, Klinikum der Universität München, Feodor-Lynen Straße 17, 81377, Munich, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Catak
authors.affiliation: Institut für Schlaganfall-und Demenzforschung (ISD), Ludwig-Maximilians-Universität LMU, Klinikum der Universität München, Feodor-Lynen Straße 17, 81377, Munich, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Janowitz
authors.affiliation: Institut für Schlaganfall-und Demenzforschung (ISD), Ludwig-Maximilians-Universität LMU, Klinikum der Universität München, Feodor-Lynen Straße 17, 81377, Munich, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Baykara
authors.affiliation: Institut für Schlaganfall-und Demenzforschung (ISD), Ludwig-Maximilians-Universität LMU, Klinikum der Universität München, Feodor-Lynen Straße 17, 81377, Munich, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Gesierich
authors.affiliation: Institut für Schlaganfall-und Demenzforschung (ISD), Ludwig-Maximilians-Universität LMU, Klinikum der Universität München, Feodor-Lynen Straße 17, 81377, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Duering
authors.affiliation: Institut für Schlaganfall-und Demenzforschung (ISD), Ludwig-Maximilians-Universität LMU, Klinikum der Universität München, Feodor-Lynen Straße 17, 81377, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Ewers
mesh_terms: D000368:Aged; D015415:Biomarkers; D001931:Brain Mapping / Q000379:methods; D002540:Cerebral Cortex / Q000503:physiopathology*; D060825:Cognitive Dysfunction / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D058245:Cognitive Reserve; D063132:Connectome / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009415:Nerve Net / Q000503:physiopathology; D009434:Neural Pathways / Q000503:physiopathology; D012016:Reference Values; D015203:Reproducibility of Results; D012146:Rest; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers
keywords: Alzheimer’s disease; Biomarker; Cognitive reserve; Global functional connectivity; Mild cognitive impairment; Resting-state fMRI