Complex Brain Network Analysis and Its Applications to Brain Disorders: A Survey

Table 6

Overview of structural brain network studies in PD.

Study	Modality	Subjects	Node definition	Edge definition	Network type	Main findings
Zhang et al., 2015 [117]	sMRI	16 PD; 20 HC	264 regions in [65]	Intracortical similarity	Binary	(1) Increased global efficiency and local efficiency in PD.; (2) Increased nodal local efficiency in the right inferior frontal gyrus (orbital part) and precentral gyrus, left insula and post cingulated cortex, and cerebellum in PD.; (3) Decreased local nodal efficiency in the right Heschl’s gyrus and precuneus gyrus, and bilateral medial superior frontal gyrus in PD.; (4) Increased global nodal efficiency in the right inferior occipital cortex, inferior frontal gyrus (orbital part), precentral gyrus, and Heschl’s gyrus in PD.
Pereira et al., 2015 [118]	sMRI	33; PD-MCI; 90; PD-HC; 56 HC	162 regions in FreeSurfer	Pearson correlation	Binary	(1) Reduced connectivity strength between cortical and subcortical regions in PD-MCI compared to HC.; (2) Larger characteristic path length and reduced global efficiency and lower regional efficiency in frontal and parietal regions in the PD-MCI group compared with other two groups.; (3) A reorganization of the highly connected regions in both PD-MCI and PD-HC.
Yadav et al., 2016 [119]	sMRI	43 PD-M; 21 PD-F; 46 HC	68 regions in FreeSurfer	Pearson correlation	Binary	(1) Lower connectivity strength and clustering coefficients and higher path length in PD-M compared with PD-F.; (2) Lower nodal betweenness in left caudal middle frontal, left rostral middle frontal, and right parahippocampal regions in PD-M compared with PD-F.; (3) Hubs were right fusiform and right isthmus cingulate region and left inferior temporal and left rostral anterior cingulate in PD-M.; (4) Hubs were right parahippocampal, right superior temporal, and left rostral middle frontal regions in PD-F.
Li et al., 2017 [120]	DTI	35 PD; 26 HC	90 regions in AAL atlas	FA	Weighted	(1) Lower connectivity strength in the feeder and local connections in PD.; (2) Decreased connections in the two modules: the limbic/paralimbic/subcortical module and the cognitive control/attention module in PD.; (3) Increased shortest path length and decreased global efficiency in PD.
Nigro et al., 2016 [121]	DTI	21 PD; 30 HC	90 regions in AAL atlas	FA × FN	Weighted	(1) Decreased network strength, global efficiency, and global clustering coefficient in PD.; (2) 14 same hub regions and 4 different hub regions between PD and HC.