Decreased Default Mode Network connectivity correlates with age-associated structural and cognitive changes.

Didac Vidal-Piã±Eiro,Nãºria Bargallã³,Sara Fernã¡Ndez-Cabello,Emilio Ros,Carme Junquã©,Elisabeth Solana,David Bartrã©S-Faz,Cinta Valls-Pedret,Roser Sala-Llonch,Eider M Arenaza-Urquijo

doi:10.3389/fnagi.2014.00256

Abstract

Ageing entails cognitive and motor decline as well as brain changes such as loss of gray (GM) and white matter (WM) integrity, neurovascular and functional connectivity alterations. Regarding connectivity, reduced resting-state fMRI connectivity between anterior and posterior nodes of the Default Mode Network (DMN) relates to cognitive function and has been postulated to be a hallmark of ageing. However, the relationship between age-related connectivity changes and other neuroimaging-based measures in ageing is fragmentarily investigated. In a sample of 116 healthy elders we aimed to study the relationship between antero-posterior DMN connectivity and measures of WM integrity, GM integrity and cerebral blood flow (CBF), assessed with an arterial spin labeling sequence. First, we replicated previous findings demonstrating DMN connectivity decreases in ageing and an association between antero-posterior DMN connectivity and memory scores. The results showed that the functional connectivity between posterior midline structures and the medial prefrontal cortex was related to measures of WM and GM integrity but not to CBF. Gray and WM correlates of anterio-posterior DMN connectivity included, but were not limited to, DMN areas and cingulum bundle. These results resembled patterns of age-related vulnerability which was studied by comparing the correlates of antero-posterior DMN with age-effect maps. These age-effect maps were obtained after performing an independent analysis with a second sample including both young and old subjects. We argue that antero-posterior connectivity might be a sensitive measure of brain ageing over the brain. By using a comprehensive approach, the results provide valuable knowledge that may shed further light on DMN connectivity dysfunctions in ageing.

Highlights

As demographic changes in developed countries push up the proportion of elderly adults in the population (Cohen, 2003), age-related cognitive decline is emerging as a major concern
MPFC-PCU Default Mode Network (DMN) CONNECTIVITY IS DECREASED IN AGED SUBJECTS First, in the between-group comparison, we found reduced DMN connectivity in ageing, between medial prefrontal cortex (mPFC) and PCU areas in which connectivity was clearly lower in the old group 0.17 (0.27) compared with the young group 0.46 (0.21)
INFLUENCE OF mPFC-PCU CONNECTIVITY ON COGNITION mPFC-PCU coupling was able to predict cognitive performance as it was significantly associated with memory factor (F = 9.047, p = 0.003; Figure 5), and with speed processing domain (F = 3.165, p = 0.023), though this last comparison did not survive Bonferroni corrections (p < 0.05/4 = 0.0125)

Summary

Introduction

As demographic changes in developed countries push up the proportion of elderly adults in the population (Cohen, 2003), age-related cognitive decline is emerging as a major concern. GM atrophy in both cortical and subcortical structures, evident as early as middle age (Salat et al, 2004), has been demonstrated in both cross-sectional (Good et al, 2001; Fjell et al, 2009b) and longitudinal evidences (Raz et al, 2004; Fjell et al, 2009a). Grey matter atrophy analyses, carried out either with Cortical Thickness (CTh) or with Voxel-based morphometry (VBM) approaches, consistently indicate that prefrontal cortices and most subcortical structures are regions of high age-related vulnerability (Good et al, 2001; Fjell et al, 2009b).

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