Influences of volume conduction on phase distributions

We investigated the influence of common sources on the distribution of relative phases between encephalographic signals. We found that common sources may only change the real part of the correlation between two analytical signals. This result implies that, in general, volume conduction has only symmetric effects on the (relative) phase distribution in that unimodal phase distributions become centered around 0 or ± π. Hence, asymmetries and/or shifts of the relative phase distribution indicate non-trivial correlations in the generating sources.