[Eeglablist] Interpolating bad channels while avoiding PCA before ICA

[Tarik S Bel-Bahar]

Greetings Mikolaj,

imho, your strategy of interpolating channels after cleaning your data,
removing bad channels, running ICA, removing some artifactual ICs,
rebuilding the EEG without those artifactual ICs [you did not mention this
step but I assume you are doing it]
and then interpolating the missing channels, sounds fine, altogether.

However, consider doing your analysis at the IC level, wherein the
independent sources in the eeg have been determined.
Further, it's not clear why there are "only" four bad channels in your
sample. In my experience, different participants have slightly different
bad channels.
Also, please note that removing artifactual ICs usually means just removing
the "blink IC" and the "lateral eye movement IC".
Removing other ICs introduces problems, as some of the weaker ICs often
seem like single channels, and throwing any IC out might also involve
inadvertantly throwing out brain dynamics related to cognition. A similar
issue arises with traditional eye-blink correction techniques that may
modify frontal channel activity that is relevant to cognition, and not just
eyeblink artifacts.

Wishing you good eeg adventures, Tarik




On Sun, May 19, 2013 at 7:11 PM, Mikołaj Magnuski <imponderabilion at gmail.com
> wrote:

> Dear EEGLab community,
>
> Given that PCA is not recommended before ICA,
> how to avoid it while still interpolating bad channels?
>
> My initial analysis of the data is in channel space
> so I would like to have all channels for all participants.
> Therefore I want to interpolate bad channels (I have a
> maximum of 4 bad channels out of 64 per subject).
> This causes the rank of the data to decrease and compli-
> cates using ICA for artifactual components removal.
>
> Do you think a following way of avoiding PCA before ICA is ok?
> 1. preprocess the data before ICA
> 2. perform ICA and remove artifactual components
> 3. interpolate channels
>
> So, in short: is it valid to interpolate channels only after
> removal of artifactual ICs?
>
> Mikolaj M
>
> _______________________________________________
> Eeglablist page: http://sccn.ucsd.edu/eeglab/eeglabmail.html
> To unsubscribe, send an empty email to
> eeglablist-unsubscribe at sccn.ucsd.edu
> For digest mode, send an email with the subject "set digest mime" to
> eeglablist-request at sccn.ucsd.edu
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sccn.ucsd.edu/pipermail/eeglablist/attachments/20130520/f1a8a359/attachment.html>