Functional connectivity between reconstructed source time series was then estimated by using coherence (see section Methods to assess brain connectivity based on phase coupling for the mathematical description of the method). Artificially inflated coherence estimates can be observed in Figure 1B where the ratio between the estimated functional connectivity values and the true value (i.e., the one obtained directly from the generated source time sources) as a function of the distance between sources 1 and 2 is shown. Values larger than 1 indicate inflated functional connectivity values due to zero-lag correlations induced by source leakage. Such an effect is more relevant when the distance between the two interacting sources is small.
