Connectivity network measures predict volumetric atrophy in mild cognitive impairment

Abstract

Alzheimer’s disease (AD) is characterized by cortical atrophy and disrupted anatomical connectivity, and leads to abnormal interactions between neural systems. Diffusion weighted imaging (DWI) and graph theory can be used to evaluate major brain networks, and detect signs of a breakdown in network connectivity. In a longitudinal study using both DWI and standard MRI, we assessed baseline white matter connectivity patterns in 30 subjects with mild cognitive impairment (MCI; mean age: 71.8+/−7.5 yrs; 18M/12F) from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Using both standard MRI-based cortical parcellations and whole-brain tractography, we computed baseline connectivity maps from which we calculated global “small-world” architecture measures, including mean clustering coefficient (MCC) and characteristic path length (CPL). We evaluated whether these baseline network measures predicted future volumetric brain atrophy in MCI subjects, who are at risk for developing AD, as determined by 3D Jacobian “expansion factor maps” between baseline and 6-month follow-up anatomical scans. This study suggests that DWI-based network measures may be a novel predictor of AD progression.

Dissociable Effects of Aging and Mild Cognitive Impairment on Bottom-Up Audiovisual Integration

“…Consistent with this view, recent neuroimaging studies have demonstrated disrupted functional connectivity within resting state brain networks not only in AD patients [21], but also in patients with MCI who are likely to progress to AD [22] and in cognitively normal elderly with high amyloid burden [23,24]. The presence of disrupted functional connectivity in early AD is also consistent with the demonstration of alterations in white matter integrity in normal individuals at high risk for AD [25,26], and with the finding that white-matter network connectivity measures predict future volumetric brain atrophy in MCI patients [27]. Taken together, these findings suggest that cognitive tasks critically dependent on effective corticocortical connectivity may be particularly sensitive to early AD pathology.…”

Amyloidosis and neurodegeneration result in distinct structural connectivity patterns in mild cognitive impairment

“…The progress of neuroimaging techniques, in particular diffusion magnetic resonance imaging (dMRI) and functional MRI, as well as post-processing (tractography) and network analysis methods, has enabled the in vivo study of the structural and functional connectivity that form the brain connectome. Connectomics has so far confirmed the impairment of network connectivity in AD observed by neuroanatomical and neuropathological studies, supporting the role of white matter degeneration in the disease, and the fact that part of the symptoms are due to disconnection of distant cortical regions (Daianu et al, 2013b(Daianu et al, , 2013aFischer et al, 2015;Mallio et al, 2015;Nir et al, 2012Nir et al, , 2015Prescott et al, 2014).…”

Magnetic resonance imaging in Alzheimer's Disease Neuroimaging Initiative 2

“…In a longitudinal study using both DWI and anatomic MRI, Nir et al [163] found that baseline DTI network measures predicted future volumetric brain atrophy in people with MCI, suggesting that DWI-based network measures may be an additional predictor of AD progression. Further work used fiber tracking (tractography) to assess the integrity of the brain’s major fiber bundles.…”