ICA with averaged data

[Robert Oostenveld]

Dear Niki

On 9 Mar 2007, at 12:01, Niki Ray wrote:
> Some of the channels (about 13, i'm using a ctf 275 system)
> have a lot of very distinct artifact that is obviously from the  
> stimulator,
> so i wanted to use one of these channels as the "ECG" channel. Is this
> sensible, or not??

The demo script on

http://www2.ru.nl/fcdonders/fieldtrip/doku.php? 
id=fieldtrip:documentation:use_independent_component_analysis_ica_to_rem 
ove_ecg_artifacts

uses the measured real ECG channel to facilitate finding the ICA  
components that represent the heart artifact. It does that by  
computing the QRS–pek triggererd average of the ICA components, and  
by computing the coherence between all ICA components and the ECG  
channel. In your case, you do not seem to have an external channel  
that can act as the ECG channel in the demo script. However,  
important is that the ECG channel is _only_ used to facilitate  
finding the heart components and it does not have a fundamental role  
in the ICA unmixing or rejection. Apparently you can detect the  
artifact components in your data in some other way, so you should be  
fine without a fake ECG channel.

best regards
Robert