Table 2:

Summary of notable graph theory-based studies in AD research.

Work	Sample	Connectivity	Main findings
Ebadi et al. (2017)	15NC, 15MCI, 15AD	Nodes: Brodmann areas SC: connection density of fiber derived from DTI	Acc: AD vs. NC = 80%, AD vs. MCI = 83.3%, MCI vs. NC = 70% AD vs NC (most important features): betweenness centrality at Brodmann Area 2, eigenvector centrality at Brodmann Area 1, load centrality at Brodmann Areas 2 and 27, and closeness centrality at Brodmann Area 1 AD vs MCI (most important features): Katz centrality at Brodmann Area 3, degree and closeness centrality at Brodmann Area 5, node redundancy coefficient and load centrality at Brodmann Area 4. MCI vs NC (most important features): hit centrality, page rank, betweenness centrality, and load centrality at Brodmann Area 6 along with hub centrality at Brodmann Area 1.
John et al. (2017)	100AD, 135NC	Nodes: 87 cortical gray matter and subcortical regions SC: correlations of the corresponding regional volumes	AD: (first sub-graph) clustering coefficient↓, sigma (the ratio between the clustering coefficient and the characteristic path length)↓ AD: (second sub-graph) Small world propensity (SWP (Feldt Muldoon et al., 2015))↑ Neurodegenerative processes impact volumetric networks in a nonglobal fashion.
Jalili (2017)	23AD, 25NC	Nodes: EEG sensor locations FC: Pearson's correlation coefficient of EEG signals	AD: local efficiency↓, modularity↓ (Global) The optimal set of measures: edge betweenness centrality, global efficiency, modularity, and synchronizability.
Dai et al. (2019)	47AD, 40NC	Nodes: AAL-611 atlas SC: connection density of fiber derived from dMRI FC: Pearson's correlation coefficient of rs-fMRI	FC of AD: clustering coefficient↓, characteristic path length↑, normalized clustering coefficient↑, normalized characteristic path length↑, and small-worldne↑ (Global) SC of AD: disrupted the characteristic path length, intramodular connections in the DMN, degree↓ in the right middle frontal gyrus, insula, and middle temporal gyrus. AD: the coupling of the FC and SC in connections of the default mode network and the rich club ↑.
Behfar et al. (2020)	15 young NC 15 senior NC 15 MCI	Nodes: Brainnetome Atlas FC: Pearson's correlation coefficient of rs-fMRI	Senior NC and MCI (compared to young NC): degree centrality (degree)↓ at 3 ROI: the right superior parietal lobule, rostral area 7 (Brainnetome label: SPL_R_5_1), the right and left precentral gyri caudal dorsolateral area 6 (Brainnetome label: PrG_R_6_2 and PrG_L_6_2) MCI (compared to Senior NC): degree centrality (degree)↓ in the right middle frontal gyrus, lateral areal 10 (Brainnetome label: MFG_R_7_7).
Protas et al. (2023)	32AD, 115MCI, 223NC	Nodes: AAL atlas tau network: the weight indicates the difference in tau deposition between two nodes	Global strength, global efficiency, and limbic strength in the tau networks are higher in AD subjects (AD > MCI > NC). Global efficiency and global strength are significantly correlated with memory in the NC group.

The arrows refer to an increase (↑) or a decrease (↓) of the indicated measures.

Abbreviations: DTI: diffusion tensor imaging; Acc: accuracy; NC: Normal control.