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. 2016 Sep;138:284–293. doi: 10.1016/j.neuroimage.2016.05.070

Fig. 1.

Fig. 1

Mean alpha-band network matrices at group level. (A) Views of single rows from the network matrices in B. Left, connection strength to the posterior cingulate cortex (seed ROI number 38, shown in green). Upper right, connection strengths to the right motor cortex (seed ROI number 24). Lower right, connection strengths to right occipital cortex (seed ROI number 24). (B) Mean network matrices, and the relative edge-level consistency, for a subset of four of the metrics under test: the absolute value of coherency between ROIs, the imaginary part of coherency, and the amplitude envelope correlation (AEC), both with and without a multivariate correction for source leakage. Lower triangles, in red, show the mean network matrix over all 183 sessions in the dataset. The colourbar to the side indicates the scale. Correlations have been converted to Z-values before averaging. The upper triangles, in blue, indicate the relative contribution of each edge to the overall consistency of group-level network estimation, computed with Eq. (13) (c.f. Fig. 2A). The two network matrices which are susceptible to source leakage (AEC and Coherence, top row) are dominated, even at group level, by a few strong edges (highlighted with arrows), and these drive the high consistency of network estimation. (C) The parcellation of 39 fMRI-derived ROIs used for this connectivity analysis (reproduced with permission from Colclough et al. (2015)). (D) Similarity between group-level network matrices. The heat map shows the high correlations between network matrices inferred at the group-level using the undirected network measures that are either immune to source leakage bias, or have been corrected for source leakage bias (starred). AEC - amplitude envelope correlation; PAEC - partial amplitude envelope partial correlation; PLI - phase lag index; wPLI - weighted phase lag index; PLV - phase locking value; MI - mutual information of phases. Coh - band-averaged coherence; IMC - band-averaged imaginary component of coherency; PCoh - partial coherence; IMPC - partial imaginary coherence.