Altered Gray Matter Structural Covariance Networks in Early Stages of Alzheimer's Disease

Abstract

Clinical symptoms observed in Alzheimer's disease (AD) patients may reflect variations within specific large-scale brain networks, modeling AD as a disconnection syndrome. The present magnetic resonance imaging study aims to compare the organization of gray matter structural covariance networks between 109 cognitively unimpaired controls (CTRL) and 109 AD patients positive to beta-amyloid at the early stages of the disease, using voxel-based morphometry. The default-mode network (DMN; medial temporal lobe subsystem) was less extended in AD patients in comparison with CTRL, with a significant decrease in the structural association between the entorhinal cortex and the medial prefrontal and the dorsolateral prefrontal cortices. The DMN (midline core subsystem) was also less extended in AD patients. Trends toward increased structural association were observed in the salience and executive control networks. The observed changes suggest that early disruptions in structural association between heteromodal association cortices and the entorhinal cortex could contribute to an isolation of the hippocampal formation, potentially giving rise to the clinical hallmark of AD, progressive memory impairment. It also provides critical support to the hypothesis that the reduced connectivity within the DMN in early AD is accompanied by an enhancement of connectivity in the salience and executive control networks.

Parcellation of the human hippocampus based on gray matter volume covariance: Replicable results on healthy young adults

“…GMV covariance examines covariation of gray matter morphology between brain regions across populations. The biological meaning of this structural covariance is not yet fully understood, but it may reflect coordinated development and/or maturational synchronization between brain regions (Alexander‐Bloch, Giedd, & Bullmore, ), and has been demonstrated as an efficient approach to test network hypotheses about brain aging/developmental mechanisms (Bergfield et al, ; DuPre & Spreng, ; Li et al, ; Montembeault et al, ; Nordin et al, ; Persson et al, ; Spreng & Turner, ; Zielinski et al, ) and clinical utility for patients (Heinze et al, ; Kim et al, ; Modinos et al, ; Montembeault, Rouleau, Provost, & Brambati, ; Seeley et al, ).…”

Radiation-Induced Changes in Structural Network in Patients with Nasopharyngeal Carcinoma

“…Mechelli et al [19] explored the covariation in the gray matter density between some regions of the brain to investigate brain symmetry, the researchers speculated that this covariation might be related with white matter fiber tracts (corpus callosum), and they suggested that covariation might be the result of mutually trophic influences or common experience related plasticity and the level of covariation might be disrupted in some patient populations. Montembeault et al [20] analyzed the gray matter structure network in early stage of Alzheimer's Disease and found that the topology architecture of the network altered. Zhu et al [21] applied the gray matter volume network to examine the effect of age.…”

Genetic interaction is associated with lower metabolic connectivity and memory impairment in clinically mild Alzheimer's disease

“…ICA has been applied to fMRI data and identified several fractionations of the DMN, of which at least 2 default mode subnetworks appear to be worth investigating . The ventral DMN (vDMN) includes the hippocampus, entorhinal cortex, and ventromedial prefrontal cortex, whereas the posterior DMN (pDMN) includes the PCC and temporoparietal cortex . These 2 subnetworks have been shown to influence distinct cognitive functions and exhibit different trajectories in longitudinal change as the disease progresses .…”