[Eeglablist] epoch baseline removal experience?

[ida miokovic]

Dear Makoto,

thank you for your answer, it cleared the doubts in my head regarding this
=). As I understood, the purpose of Baseline Removal is for me/us to have
better insight when event in observed epoch happened, so the value around
corresponding marker is expected to be zero. Right?

I have one more question regarding this - does it matter if I Remove
Baseline for example (-1000ms to 0ms) if I have epoch that is longer (-4
secs to 4 secs)? I read in Q&A list Arno's answer regarding similar
question where he said that ICA can be unstable if the epochs baseline is
too short, so he suggests longer baselines (i.e 1 sec).

Thanks,

Ida

On Thu, May 10, 2012 at 9:45 PM, Makoto Miyakoshi <mmiyakoshi at ucsd.edu>wrote:

> Dear Ida,
>
> The consequence would be that you may not have near-zero potential
> at/around time zero (and this time zero which should be an onset of
> whatever event). Usually people want to reset their data to zero
> microvolt at/around time zero, so they subtract mean of short time
> period immediately before it (for example, -200 ms to 0 ms as a
> baseline period). Am I answering to your question? If not, let me
> know.
>
> Makoto
>
> 2012/5/10 ida miokovic <ida.miokovic at gmail.com>:
> > Hello everyone,
> >
> > Since I do not have experience in eeg signal processing, I am asking you
> for
> > the opinion regarding epoch baseline removal (a window for this pops up
> > after I do the data epoching). Epochs I am extracting are quite long: -4
> > secs before and 4 secs after Marker of my interest.
> >
> > Why is following suggested in tutorial:
> >
> > "Using the mean value in the pre-stimulus period (the pop_rmbase()
> default)
> > is effective for many datasets, if the goal of the analysis is to define
> > transformations that occur in the data following the time-locking
> events."
> >
> > What are the consequences if I leave the fields in pop up window (Epoch
> > Baseline Removal) empty and therefore have the whole epoch used as a
> > baseline?
> >
> > Thank you in advance,
> >
> > All the best,
> >
> > Ida
> >
> >
> >
> >
> >
> >
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>
>
> --
> Makoto Miyakoshi
> JSPS Postdoctral Fellow for Research Abroad
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
>
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