[Eeglablist] re-epoching, ICA selected periods

Tarik S Bel-Bahar tarikbelbahar at gmail.com
Fri Mar 3 12:25:53 PST 2017


Hello Jose,

Yes you should be able to re-epoch, then run ICA on just the epochs without
the buffer time,
and then re-apply the ICA results to the files with the buffer time, and go
from there.
You may have to insert a new trigger, but you should be able to just
"select an epoch start/end time that does include the buffer times. First
try it with one file from the gui, and use eegh to build a script for that.

Overall, if your buffer time is under ~2 seconds, and has no large
artifacts, it would be okay to include them in the ICA. In other words,
your ICA results should look very similar with either method (with or
without the buffer periods).

Check Makoto's general recommendations for ICA just in case, if you haven't
had a chance to.





On Fri, Mar 3, 2017 at 10:11 AM, José Luis <joseluisulloafulgeri at gmail.com>
wrote:

> hi,
>
> I'm analysing EEG data and want to perform ERP and time-frequency analyses,
> I'm doing the pre-processing with EEGlab,
> I wanted to move fast so I epoch my data and then I proceed with the
> artefact rejection. I epoch my data taken into consideration that for
> time-frequency I need a buffer zone,
> Now, I want to perform ICA but only in a selected time period of interest.
> I have several question here:
> 1) Can I do ICA in select periods of time within my epochs?
> 2) If not, I could try to re-epoch my dataset, perform ICA in the
> re-epoched (shorter) dataset, and then re-inject the weight of the ICA back
> to the original dataset), does that sound ok? I'm only interested in my
> selected time period of interest, and the rest of the signal I would use it
> because I need a buffer zone, and because long periods to compute power at
> low frequencies,
> 3) Can I epoch relative to two triggers, i.e. for a sequence of triggers:
> A, B, C, D, E I want to do from -0.5 relative to A until E,
>
> Thanks in advance for your help,
> Jose
>
> --
> José Luis ULLOA FULGERI, PhD
> +32477429007 <+32%20477%2042%2090%2007>
> +32492646477
> https://sites.google.com/site/joseluisulloafulgeri/
>
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