and NX′,Y′ represent the two nodes whose connection comprised the edges, for a total of 2,145 edges between each pair of nodes in each frequency band. Each edge was characterized by two complementary measures: 1) connection strength , which is the coherence value between the two nodes; and, 2) connection length , which represents the physical distance between the two nodes comprising the connection. Lengths were calculated from the Cartesian coordinate map (Figure 1) according to the formulaFinally, the degree of each node (also known as overall node connectivity) was calculated, defined as the average of the coherence values for a node with the other 65 nodes according to the formulaThe median values of connection strengths (CE) were compared for the two groups in each frequency band using the Kruskal Wallis test. The median length values (LE) of those connections that showed differences in strength also were compared for the two groups in each frequency band using the Kruskal Wallis test. To identify MDD related hub nodes, Student's t-test was used to test whether the mean node degree (DN) in MDD subjects differed from that in controls. A strict Bonferroni correction of 2.33×10−5 (0.05/2,145) was imposed on all analyses involving
