[Eeglablist] baseline correction

Makoto Miyakoshi mmiyakoshi at ucsd.edu
Tue Sep 2 11:36:49 PDT 2014

Dear Angel,

Good skepticism.
You can run a simple experiment with STUDY to see whether it really
subtract the baseline.

1. precompute ONLY ERP
2. set baseline period to a) -200 to 0 ms b) entire epoch length, to see
the difference in the end (i.e. after clustering)

Because here you are only dealing with ERP precompute and clustering should
not take too long time.


On Fri, Aug 29, 2014 at 4:23 AM, Angel Tabullo <angeltabullo at yahoo.com>

> Thanks for the reply, it was helpful. However: can anyone confirm that the
> baseline parameter in the "Precompute channel measures" window actually
> removes the baseline from the data? Because I just assumed it, but could
> not find it in any tutorial.
>   El Jueves, 28 de agosto, 2014 22:27:51, bjj2909102003 <
> bjj2909102003 at 163.com> escribió:
>  Hello,Angel.
> Firstly, if you already had baseline correction, it was not necesssary to
> repeat. And even you repeated it, it did not bring big influences for your
> data.
> Secondly,in my opinion, precompute ERPs was necessary for guys who did
> not have baseline correction.
> In a word, precompute ERPs(baseline correction) is reasonable!
> ------------------------------
> bjj2909102003
> *From:* Angel Tabullo <angeltabullo at yahoo.com>
> *Date:* 2014-08-27 23:13
> *To:* eeglablist at sccn.ucsd.edu
> *Subject:* [Eeglablist] baseline correction
> Hi everyone! I have a doubt regarding how ERP manages baseline correction
> in individual datasets and study data.
> Everytime I epoch individual data, extract the epochs that correspond to
> each experimental condition and save them in separate datasets, I use the
> "Remove Baseline" Tool ("rmbase") to sustract the mean value of the
> prestimulus period from the epochs.  However, EEGLAB offers another
> instance of baseline removal when precomputing channel measures for STUDY
> data. When you choose to precompute ERPs,  you can indicate the time window
> for the baseline correction. My question is: is it necessary to repeat this
> baseline correction step when calculating the grand average with the study
> data if you already removed baseline mean values from individual epoched
> data?
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Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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