[Eeglablist] Conducting ICA on correct or all epochs

[David Groppe]

Hi Baris,
   ICA's performance will generally degrade as the number of
electrical sources increases (see
http://www.cogsci.ucsd.edu/~dgroppe/PUBLICATIONS/GroppeCSO2008.pdf).
The incorrect trials probably have some EEG activity not present (or
at least less present) in the correct trials.  So if you have
sufficient data to run ICA on just the correct trials, it would
probably be better just to use the correct trials.  If you don't have
enough data using just the correct trials though, you'll probably be
fine using the all the trials, since surely a lot of the EEG activity
is common to both sets of trials.
         hope this helps,
             -David Groppe


On Wed, Nov 10, 2010 at 4:19 PM, Baris Demiral
<demiral.007 at googlemail.com> wrote:
> Hi everyone,
> I am running a simple EEG experiment where I measure reaction times and
> accuracies.
> I want to use ICs for artifact removal, and I will report only the correct
> trials (hits).
> So would it be better to use the correct epochs for the ICA to correct for
> the artifacts or is it OK to use all the epochs to detect the artifacts and
> then run the artifact correction (pop_subcomp) followed by deleting the
> incorrect epochs?
> Thanks,
> Baris
>
> --
> SB Demiral, PhD.
> Department of Psychology
> 7 George Square
> The University of Edinburgh
> Edinburgh, EH8 9JZ
> UK
> Phone: +44 (0131) 6503063
>
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-- 
David Groppe, Ph.D.
dgroppe at cogsci.ucsd.edu
http://www.cogsci.ucsd.edu/~dgroppe/