[Eeglablist] Interpolation and ICA

Arnaud Delorme arno at ucsd.edu
Tue Jan 5 13:12:22 PST 2010


Dear Bernhard,


> As I need to use the algorithm eeg_interp(EEG, Channel, 'spherical')  
> for
> channel-interpolation in combination with ICA I found a possible
> contradiction regarding the question what to apply first, ICA or
> interpolation.


Apply ICA first. Once you have run ICA you may (1) remove artifactual  
ICA components if this is what you want to do (2) then interpolate  
channels.

If you interpolate channels first, the rank of the data might not be  
equal to the number of channel. Even if it is (because spherical  
interpolation is not linear interpolation), you have introduced some  
non-linearity in the data (in the sense that an underlying source  
might not project linearly to scalp channels any more) and this is  
going to make the ICA solution more noisy.

Best,

Arno



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