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Link to original content: https://pubmed.ncbi.nlm.nih.gov/37551987/
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. 2023 Nov;13(9):553-562.
doi: 10.1089/brain.2023.0013. Epub 2023 Sep 19.

Structural Network Topology Reveals Higher Brain Resilience in Individuals with Preclinical Alzheimer's Disease

Qianyun Chen  1 , Jill Abrigo  1 , Min Deng  1 , Lin Shi  1 , Yi-Xiang Wang  1 , Winnie C W Chu  1
Affiliations

Structural Network Topology Reveals Higher Brain Resilience in Individuals with Preclinical Alzheimer's Disease

Qianyun Chen et al. Brain Connect. 2023 Nov.

Abstract

Introduction: The diagnosis of Alzheimer's disease (AD) requires the presence of amyloid and tau pathology, but it remains unclear how they affect the structural network in the pre-clinical stage. We aimed to assess differences in topological properties in cognitively normal (CN) individuals with varying levels of amyloid and tau pathology, as well as their association with AD pathology burden. Methods: A total of 68 CN individuals were included and stratified by normal/abnormal (-/+) amyloid (A) and tau (T) status based on positron emission tomography results, yielding three groups: A-T- (n = 19), A+T- (n = 28), and A+T+ (n = 21). Topological properties were measured from structural connectivity. Group differences and correlations with A and T were evaluated. Results: Compared with the A-T- group, the A+T+ group exhibited changes in the structural network topology. At the global level, higher assortativity was shown in the A+T+ group and was correlated with greater tau burden (r = 0.29, p = 0.02), while no difference in global efficiency was found across the three groups. At the local level, the A+T+ group showed disrupted topological properties in the left hippocampus compared with the A-T- group, characterized by lower local efficiency (p < 0.01) and a lower clustering coefficient (p = 0.014). Conclusions: The increased linkage in the higher level architecture of the white matter network reflected by assortativity may indicate increased brain resilience in the early pathological state. Our results encourage further investigation of the topological properties of the structural network in pre-clinical AD.

Keywords: Alzheimer's disease; assortativity; diffusion tensor imaging; graph theory; structural connectivity; tractography.

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Conflict of interest statement

No competing financial interests exist.

Figures

FIG. 1.
FIG. 1.
(A) Flowchart of the brain network construction from DWI. (B) Illustration of the structural brain network. The nodes in the network are represented by circles, which correspond to anatomical regions. The edges, depicted as connecting lines between the circles, represent the connections between these regions. DWI, diffusion-weighted imaging.
FIG. 2.
FIG. 2.
Global topological properties. Mean values of global efficiency (A) and assortativity (B) are shown for A−T− (green), A+T− (blue), and A+T+ (red) groups at different network densities. *Indicates statistical differences between A−T− and A+T− (blue) groups, between A−T− and A+T+ (green) groups, and between A+T− and A+T+ (red) groups. Further details on the statistical differences are shown in Supplementary Table S1. A, amyloid; T, tau.
FIG. 3.
FIG. 3.
(A) The graph shows the largest connected component size of the network in A−T− (green line), A+T− (blue line), and A+T+ (red line) groups as a function of network density. The largest component size tends to increase with higher density. The dashed line indicates the lowest density threshold (7.8%) in which networks of the 3 groups included all nodes (i.e., 82 regions). Local topological properties of the hippocampus such as degree (B), local efficiency (C), and clustering coefficient (D) were calculated under the density threshold of 7.8%. Significant differences in local efficiency and clustering coefficient in the left hippocampus were found between the A+T+ and A−T− groups. The box plots show the median and interquartile range. A−/A+, negative/positive amyloid-PET; L, left; PET, positron emission tomography; R, right; T−/T+, negative/positive tau-PET.
FIG. 4.
FIG. 4.
Scatter plot showing the correlation between assortativity and global amyloid-PET SUVR (left) and between assortativity and tau-PET SUVR in the temporal meta-ROI (right). Temporal meta-ROI includes amygdala, entorhinal, fusiform, and inferior temporal and middle temporal gyri. ROI, region of interest; SUVR, standardized uptake value ratio.
See this image and copyright information in PMC

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