[Eeglablist] using ica weights in Matlab

[Jason Palmer]

Hi Jeff,

 

You are missing the EEG.icasphere matrix:

 

                comp_acts = EEG.icaweights * EEG.icasphere * EEG.data;

                EEG.icawinv = pinv( EEG.icaweights*EEG.icasphere );

 

-Jason

 

 

From: eeglablist-bounces at sccn.ucsd.edu
[mailto:eeglablist-bounces at sccn.ucsd.edu] On Behalf Of Jeff Eriksen
Sent: Friday, June 24, 2011 5:47 PM
To: eeglablist at sccn.ucsd.edu
Subject: [Eeglablist] using ica weights in Matlab

 

I am hoping to do some specialized processing in Matlab using the icawinv
and icaweights, part of the the ALLEEG Matlab structure. First I tried to
reconstruct the EEG with one component removed but it did not look quite
right. Next I decided to leave all components in and see if I could
construct all the component time courses and then use them to reconstruct
the whole EEG epoch. This did not come out right either. To get the
components, I do this:

 

comp_acts = ica_weights * eeg

 

Then to get the EEG back I do this:

 

eeg-recon = icawinv * comp_acts

 

But find that the reconstructed EEG does not quire match the original EEG,
and is much larger in amplitude as well.

 

I must not be understanding fully what these matrices are.

 

Thanks,

-Jeff

 

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