Anatomical connectivity mapping: a new tool to assess brain disconnection in Alzheimer's disease

Bozzali, Marco, Parker, Geoffrey J M, Serra, Laura, Embleton, Karl, Gili, Tommaso, Perri, Roberta, Caltagirone, Carlo and Cercignani, Mara (2011) Anatomical connectivity mapping: a new tool to assess brain disconnection in Alzheimer's disease. NeuroImage, 54 (3). pp. 2045-2051. ISSN 1095-9572

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Abstract

Previous studies suggest that the clinical manifestations of Alzheimer's disease (AD) are not only associated with regional gray matter damage but also with abnormal functional integration of different brain regions by disconnection mechanisms. A measure of anatomical connectivity (anatomical connectivity mapping or ACM) can be obtained by initiating diffusion tractography streamlines from all parenchymal voxels and then counting the number of streamlines passing through each voxel of the brain. In order to assess the potential of this parameter for the study of disconnection in AD, we computed it in a group of patients with AD (N=9), in 16 patients with amnestic mild cognitive impairment (a-MCI, which is considered the prodromal stage of AD) and in 12 healthy volunteers. All subjects had an MRI scan at 3T, and diffusion MRI data were analyzed to obtain fractional anisotropy (FA) and ACM. Two types of ACM maps, absolute count (ac-ACM) and normalized by brain size count (nc-ACM), were obtained. No between group differences in FA surviving correction for multiple comparison were found, while areas of both decreased (in the supramarginal gyrus) and increased (in the putamen) ACM were found in patients with AD. Similar results were obtained with ac-ACM and nc-ACM. ACM of the supramarginal gyrus was strongly associated with measures of short-term memory in healthy subjects. This study shows that ACM provides information that is complementary to that offered by FA and appears to be more sensitive than FA to brain changes in patients with AD. The increased ACM in the putamen was unexpected. Given the nature of ACM, an increase of this parameter may reflect a change in any of the areas connected to it. One intriguing possibility is that this increase of ACM in AD patients might reflect processes of brain plasticity driven by cholinesterase inhibitors.

Item Type: Article
Keywords: Diffusion;Alzheimer's disease;Mild cognitive impairment; Disconnection;Short-term memory
Schools and Departments: Brighton and Sussex Medical School > Clinical and Laboratory Investigation
Subjects: R Medicine > RC Internal medicine > RC0321 Neurosciences. Biological psychiatry. Neuropsychiatry
R Medicine > RC Internal medicine > RC0321 Neurosciences. Biological psychiatry. Neuropsychiatry > RC0346 Neurology. Diseases of the nervous system Including speech disorders
Depositing User: Mara Cercignani
Date Deposited: 24 Apr 2012 12:03
Last Modified: 29 Oct 2012 14:25
URI: http://sro.sussex.ac.uk/id/eprint/7533
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