title: Characteristics of the default mode functional connectivity in normal ageing and Alzheimer's disease using resting state fMRI with a combined approach of entropy-based and graph theoretical measurements.
abstract: Cognitive decline in normal ageing and Alzheimer's disease (AD) emerges from functional disruption in the coordination of large-scale brain systems sustaining cognition. Integrity of these systems can be examined by correlation methods based on analysis of resting state functional magnetic resonance imaging (fMRI). Here we investigate functional connectivity within the default mode network (DMN) in normal ageing and AD using resting state fMRI. Images from young and elderly controls, and patients with AD were processed using spatial independent component analysis to identify the DMN. Functional connectivity was quantified using integration and indices derived from graph theory. Four DMN sub-systems were identified: Frontal (medial and superior), parietal (precuneus-posterior cingulate, lateral parietal), temporal (medial temporal), and hippocampal (bilateral). There was a decrease in antero-posterior interactions (lower global efficiency), but increased interactions within the frontal and parietal sub-systems (higher local clustering) in elderly compared to young controls. This decreased antero-posterior integration was more pronounced in AD patients compared to elderly controls, particularly in the precuneus-posterior cingulate region. Conjoint knowledge of integration measures and graph indices in the same data helps in the interpretation of functional connectivity results, as comprehension of one measure improves with understanding of the other. The approach allows for complete characterisation of connectivity changes and could be applied to other resting state networks and different pathologies.
authors.affiliation: Montreal Neurological Institute, McConnell Brain Imaging Centre, McGill University, Montréal, Québec, Canada; Laboratoire International de Neuroimagerie et Modélisation, Montréal, Québec, Canada. Electronic address: paule.toussaint@mcgill.ca.
authors.forename: Paule-Joanne
authors.initials: PJ
authors.lastname: Toussaint
authors.affiliation: Laboratoire d'Imagerie Fonctionnelle, UMR-S 678, INSERM-UPMC, Paris, France.
authors.forename: Sofiane
authors.initials: S
authors.lastname: Maiz
authors.affiliation: Laboratoire d'Imagerie Fonctionnelle, UMR-S 678, INSERM-UPMC, Paris, France.
authors.forename: David
authors.initials: D
authors.lastname: Coynel
authors.affiliation: Laboratoire International de Neuroimagerie et Modélisation, Montréal, Québec, Canada; Centre de Recherche de l'Institut de Gériatrie de l'Université de Montréal, Montréal, Québec, Canada.
authors.forename: Julien
authors.initials: J
authors.lastname: Doyon
authors.affiliation: Laboratoire d'Imagerie Fonctionnelle, UMR-S 678, INSERM-UPMC, Paris, France; Laboratoire International de Neuroimagerie et Modélisation, Montréal, Québec, Canada.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Messé
authors.affiliation: Groupe Hospitalier Pitié-Salpêtrière, Laboratoire de Neuro-psychologie, Paris, France.
authors.forename: Leonardo Cruz
authors.initials: LC
authors.lastname: de Souza
authors.affiliation: Groupe Hospitalier Pitié-Salpêtrière, Laboratoire de Neuro-psychologie, Paris, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Sarazin
authors.affiliation: Laboratoire d'Imagerie Fonctionnelle, UMR-S 678, INSERM-UPMC, Paris, France; Laboratoire International de Neuroimagerie et Modélisation, Montréal, Québec, Canada.
authors.forename: Vincent
authors.initials: V
authors.lastname: Perlbarg
authors.affiliation: Laboratoire d'Imagerie Fonctionnelle, UMR-S 678, INSERM-UPMC, Paris, France; Laboratoire International de Neuroimagerie et Modélisation, Montréal, Québec, Canada; Groupe Hospitalier Pitié-Salpêtrière, Service de Médecine Nucléaire, Paris, France.
authors.forename: Marie-Odile
authors.initials: MO
authors.lastname: Habert
authors.affiliation: Laboratoire d'Imagerie Fonctionnelle, UMR-S 678, INSERM-UPMC, Paris, France; Laboratoire International de Neuroimagerie et Modélisation, Montréal, Québec, Canada.
authors.forename: Habib
authors.initials: H
authors.lastname: Benali
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D000544:Alzheimer Disease / Q000503:physiopathology*; D001921:Brain / Q000502:physiology / Q000503:physiopathology*; D063132:Connectome / Q000379:methods*; D003627:Data Interpretation, Statistical; D019277:Entropy; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000502:physiology / Q000503:physiopathology*; D055815:Young Adult
keywords: Alzheimer's disease; Functional connectivity; Functional networks; Graph theoretical analysis; Hierarchical integration; Normal ageing