A review of structural and functional brain networks: small world and atlas

Abstract

Brain networks can be divided into two categories: structural and functional networks. Many studies of neuroscience have reported that the complex brain networks are characterized by small-world or scale-free properties. The identification of nodes is the key factor in studying the properties of networks on the macro-, micro- or mesoscale in both structural and functional networks. In the study of brain networks, nodes are always determined by atlases. Therefore, the selection of atlases is critical, and appropriate atlases are helpful to combine the analyses of structural and functional networks. Currently, some problems still exist in the establishment or usage of atlases, which are often caused by the segmentation or the parcellation of the brain. We suggest that quantification of brain networks might be affected by the selection of atlases to a large extent. In the process of building atlases, the influences of single subjects and groups should be balanced. In this article, we focused on the effects of atlases on the analysis of brain networks and the improved divisions based on the tractography or connectivity in the parcellation of atlases.

Keywords: Atlas; Brain networks; Small world.

Fig. 1

The construction of functional and structural networks

Fig. 2

This figure shows information on the AAL, EZ, TT, HO, CC200, CC400, Brodmann (BA) and LPBA40 atlases [21, 62]

Fig. 3

The parcellation process based on DTI and functional connectivity. This figure shows parcellations of the substantia nigra [64], Broca’s area [65] and left inferior parietal lobule [66] based on DTI and parcellations of the human orbitofrontal cortex based on resting-state fMRI [71]