[Eeglablist] CSD vs ICA

[Scott Makeig]

Both CSD and ICA are linear spatial filtering methods - but with 
different assumptions, and therefore different results.

If the EEG volume conduction of interest were all radial, then 
CSD/Laplacian filtering would sharpen it and in so doing would make 
potentials from spatially distinct sources more distinct on the scalp.

However, this is only true for gyral/radial sources -- whereas most 
sources (and >2/3? of cortical area) are not gyral and not radially 
oriented.

ICA spatial filtering, on the other hand, can (given enough data, etc) 
recover the true projection of the source to the scalp - no matter what 
it's orientation, precisely by separating its field energy from the 
energies of other sources.


Scott Makeig