Cognitive Reserve in Mild Cognitive Impairment: structural and functional imaging correlates

Abstract

AbstractBackgroundThe term “Cognitive Reserve” (CR) refers to the ability of the brain to cope with the damage in order to minimize symptomatology. Several studies have shown controversial data about functional and structural correlates of CR in normal and pathological aging, probably due to the use of different CR proxies (level of education, occupational complexity, participation in leisure activities, IQ, verbal abilities or intelligence, heterogeneous fMRI tasks). The aim of this study was to investigate imaging correlates of different aspects of CR in a sample of patients with Mild Cognitive Impairment (MCI).MethodPatients with a diagnosis of MCI and young onset of cognitive symptoms (< 65) answered the Cognitive Reserve Index questionnaire (CRIq) aimed at measuring cognitive reserve acquired during lifetime. Patients also underwent multimodal Magnetic Resonance Imaging (MRI) on a 3T scanner including high‐resolution T1 and functional MRI sequences acquired at rest (resting fMRI). CRIq‐Total score and single subscores (CRIq‐Education, ‐WorkingActivity and ‐LeisureTime) were related to regional grey matter (GM) volume, whole brain fractional anisotropy (FA) and functional connectivity of resting‐state networks (RSNs) using, respectively, Voxel Based Morphometry (VBM), Tract‐Based Spatial Statistics (TBSS), and independent component analysis of resting fMRI (MELODIC).ResultThirty‐nine patients were recruited. The median CRIq‐Total, ‐Education, ‐WorkingActivity and ‐LeisureTime scores were respectively 102, 97, 105 and 105. VBM correlational analysis showed no significant results. TBSS revealed a negative correlation between CRIq‐LeisureTime and FA of the body of corpus callosum. Resting‐fMRI analyses revealed negative correlations between CRIq scores and functional connectivity, involving particularly frontal and temporal areas.ConclusionIn patients with MCI, cognitive reserve relates to functional connectivity of fronto‐temporal areas rather than to structural variability (grey matter atrophy or white matter microstructural integrity). The negative correlations found between functional connectivity and CRIq scores shows that patients with high cognitive reserve may not need to increase functional connectivity.