The node degree, ND, of a node is the number of connections that link it to the rest of the network. It is the most fundamental network measure, and most other measures are ultimately linked to it. The node efficiency, NE, for a given node i is defined as the inverse of the mean harmonic shortest path length between this node and all other nodes in the network [35], [36]:It measures the ability of a node to propagate information with the other nodes in a network. The node betweenness, NB, of a given node i is defined as [46]:where σj,k is the number of shortest geodesic paths between nodes j and k, and σj,k(i) is the number of shortest geodesic paths between nodes j and m, which pass through node i. It captures the influence that one node has over the flow of information between all other nodes in the network. In this study, we normalized the regional nodal parameters of a node by the average value of all nodes. A node with high value (>mean + SD) in any of the regional nodal parameters was considered as a hub in the network [47], [48].
