Figure 1.
Organization of the network nodes at three different scales.
The Sensor Net locations that match the positions of the International 10–10 System are labeled and followed by the numbers of the Sensor Net. The sensors corresponding to the 10–20 System are shown with grey circles. The size of the network is (a) N = 111, i.e., each individual sensor is used as a network node; (b) N = 55, i.e., pairs of sensors are used as network nodes; (c) N = 19, i.e., the International 10–20 System locations together with their first neighborhoods are used as network nodes (in computing S-estimator between any two group, their common nodes are removed).
Figure 2.
Construction of brain networks from EEG signals.
The top plot shows sample EEGs taken over a time period of one second. The next step is to compute pair-wise correlations to obtain the weighted cross-correlation matrix (rows and column represent nodes). Then, the matrix is reduced to a binary form by comparing each entry with a threshold (the threshold is set such that the network has a specific density); the links with correlation values less than the threshold are set to 0; others to 1. Finally, graph theoretical metrics are calculated for the binary network.
Figure 3.
Clustering coefficient of the network as a function of network cost for different network sizes (N = 111, 55, and 19).
Mean values of clustering coefficient are plotted for different frequency bands including delta (1–3 Hz), theta (3–7 Hz), alpha (7–13 Hz), beta (13–30 Hz). The dots above the plots represent statistically significant difference at P<0.05 (Wilcoxon's ranksum test).
Figure 4.
Network modularity as a function of network cost for different network sizes.
Other designations are as in Fig. 3.
Figure 5.
Efficiency of the network as a function of network cost for different network sizes.
Other designations are as in Fig. 3.
Figure 6.
Economic efficiency of the network (i.e. efficiency minus cost) as a function of network cost for different network sizes.
Other designations are similar to Fig. 3.
Figure 7.
Network assortativity as a function of network cost for different network sizes.
Other designations are as in Fig. 3.