The observed differences in alpha were robust, and used methods that unambiguously localized the effect to posterior EEG generators. Another fundamental advantage of CSD-fPCA is that it improves the quality of the data by separating and removing sources of artifact. For example, electromyogram and residual electrooculogram, which are broadly distributed and vary with the recording reference, are isolated as separate CSD factors (cf. Fig. S1 in the Supplement). Although the generators of these factors may largely be outside the braincase and might otherwise obscure the effects reported here, they nevertheless represent physiological activity that could be separately explored by CSD-fPCA.4
