title: Structural hippocampal network alterations during healthy aging: a multi-modal MRI study.
abstract: While hippocampal atrophy has been described during healthy aging, few studies have examined its relationship with the integrity of White Matter (WM) connecting tracts of the limbic system. This investigation examined WM structural damage specifically related to hippocampal atrophy in healthy aging subjects (n = 129), using morphological MRI to assess hippocampal volume and Diffusion Tensor Imaging (DTI) to assess WM integrity. Subjects with Mild Cognitive Impairment (MCI) or dementia were excluded from the analysis. In our sample, increasing age was significantly associated with reduced hippocampal volume and reduced Fractional Anisotropy (FA) at the level of the fornix and the cingulum bundle. The findings also demonstrate that hippocampal atrophy was specifically associated with reduced FA of the fornix bundle, but it was not related to alteration of the cingulum bundle. Our results indicate that the relationship between hippocampal atrophy and fornix FA values is not due to an independent effect of age on both structures. A recursive regression procedure was applied to evaluate sequential relationships between the alterations of these two brain structures. When both hippocampal atrophy and fornix FA values were included in the same model to predict age, fornix FA values remained significant whereas hippocampal atrophy was no longer significantly associated with age. According to this latter finding, hippocampal atrophy in healthy aging could be mediated by a loss of fornix connections. Structural alterations of this part of the limbic system, which have been associated with neurodegeneration in Alzheimer's disease, result at least in part from the aging process.
authors.affiliation: University of Bordeaux, INCIA, UMR 5287 Talence, France ; CNRS, INCIA, UMR 5287 Talence, France ; EPHE Bordeaux, France.
authors.forename: Amandine
authors.initials: A
authors.lastname: Pelletier
authors.affiliation: University of Bordeaux, INCIA, UMR 5287 Talence, France ; CNRS, INCIA, UMR 5287 Talence, France ; CHU de Bordeaux, Service de Médecine Nucléaire Bordeaux, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Periot
authors.affiliation: University of Bordeaux, INCIA, UMR 5287 Talence, France ; CNRS, INCIA, UMR 5287 Talence, France.
authors.forename: Bixente
authors.initials: B
authors.lastname: Dilharreguy
authors.affiliation: RMSB, UMR 5536 Bordeaux, France.
authors.forename: Bassem
authors.initials: B
authors.lastname: Hiba
authors.affiliation: University of Bordeaux, INCIA, UMR 5287 Talence, France ; CNRS, INCIA, UMR 5287 Talence, France ; CHU de Bordeaux, Service de Médecine Nucléaire Bordeaux, France.
authors.forename: Martine
authors.initials: M
authors.lastname: Bordessoules
authors.affiliation: Université de Bordeaux, ISPED, Centre ISPED, INSERM U 897 Bordeaux, France.
authors.forename: Karine
authors.initials: K
authors.lastname: Pérès
authors.affiliation: Université de Bordeaux, ISPED, Centre ISPED, INSERM U 897 Bordeaux, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Amieva
authors.affiliation: Université de Bordeaux, ISPED, Centre ISPED, INSERM U 897 Bordeaux, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Dartigues
authors.affiliation: University of Bordeaux, INCIA, UMR 5287 Talence, France ; CNRS, INCIA, UMR 5287 Talence, France ; EPHE Bordeaux, France ; CHU de Bordeaux, Service de Médecine Nucléaire Bordeaux, France.
authors.forename: Michèle
authors.initials: M
authors.lastname: Allard
authors.affiliation: University of Bordeaux, INCIA, UMR 5287 Talence, France ; CNRS, INCIA, UMR 5287 Talence, France ; EPHE Bordeaux, France.
authors.forename: Gwénaëlle
authors.initials: G
authors.lastname: Catheline
keywords: DTI; cingulum; fornix; healthy aging; hippocampal atrophy; limbic system; mode of anisotropy