Identification of the functional modules in the human brain structural network. (a) (Top panel) The binarized matrix represents the human brain structural network constructed using cortical thickness from MRI (He, Chen, et al. 2007). (Bottom panel) Each suprathreshold cell in the top panel represents 1 “link” in the brain network. (1,2) SFG, (3,4) MFG, (5,6) IFG, (7,8) MdFG, (9,10) PrCG, (11,12) LOFG: lateral frontoorbital gyrus, (13,14) MOFG, (15,16) SPL, (17,18) SMG, (19,20) ANG: angular gyrus, (21,22) PCU: precuneus gyrus, (23,24) PoCG, (25,26) STG, (27,28) MTG, (29,30) ITG: inferior temporal gyrus, (31,32) UNC: uncus, (33,34) MOTG: medial occipitotemporal gyrus, (35,36) LOTG, (37,38) PHG: parahippocampal gyrus, (39,40) OP: occipital pole, (41,42) SOG: superior occipital gyrus, (43,44) MOG: middle occipital gyrus, (45,46) IOG: inferior occipital gyrus, (47,48) CUN: cuneus, (49,50) LING, (51,52) CING: cingulate region, (53,54) INS: insula. (b) Progress of the network modularity, Q, as regions are merged into modules for the human cortical network (blue) and 1000 random networks (dotted). Red down arrow indicates the cortical network modularity reaches maximum when the network is segmented into 6 modules (Z score = 7.9). The network modularity decreases as the merge continues indicating a less optimized network modular organization. (c) Dendrogram representation of the modules identification progress determined by modularity (Q). The maximum Q is reached when the network is separated into 6 modules indicated by the red up arrow.

Modular architecture of the human cortical network. Six modules of human cortical network displayed in groups. Red: module I, orange: module II, pink: module III, blue: module IV, yellow: module V, green: module VI. The intermodular connections and intramodular connections of the network are shown in dark and gray lines, respectively. The size of each node denotes the relative betweenness centrality (N_bc) of the cortical region in the brain network (for details, see Table 1).