[Eeglablist] Rereference EEG reference using reref

Wed Nov 13 15:06:48 PST 2013

David,

My understanding is that you have 32 channel data, and want to add a 33rd channel at the location of the reference electrode. Upon completion the initial 32 channels will be re-referenced by having the average reference subtracted from each of them. The 33rd channel will contain the average, at each time frame, of the original 32 channels.

I do not know if EEGlab supports this natively, but having it expressed as I did above may help other people tell you how to accomplish it.

I believe, though, that you should NOT do this if your intent is to improve some type of classification, as the 33rd channel will not add any information that will help the classification. It does add a bit of spatial information that MAY help a little with source modeling.

I do not believe you are asking about any type of interpolation. Adding any interpolated channels to use for classification or statistics is just wrong. About the only thing you need interpolation for is plotting purposes to make smooth topographies.

-Jeff

-----Original Message-----
From: eeglablist-bounces at sccn.ucsd.edu on behalf of Tarik S Bel-Bahar
Sent: Tue 11/12/2013 3:45 PM
To: David Kaufman
Cc: eeglablist
Subject: Re: [Eeglablist] Rereference EEG reference using reref

Greetings David,
hope this might help you: what it seems you need is an
interpolating function. Check the specifications which
should help you decide what to enter into the function.
Double-check that you re-reference appropriately
before interpolating, and that you're not including too many
bad channels around the reference of course.
You can search all of the below on google in
case the links don't come through for the function descriptions
and for the eeglab list queries listed below.

eeg_interp.m <http://sccn.ucsd.edu/eeglab/allfunctions/eeg_interp.m>
sccn.ucsd.edu/*eeglab*/all*functions*/eeg_interp.m
pop_interp.m - *eeglab* - Advanced EEG/MEG signal processing
*...*<http://code.google.com/p/eeglab/source/browse/eeglab/functions/popfunc/pop_interp.m?r=9707>
code.google.com/p/*eeglab*/source/.../*eeglab*/*functions*
/.../pop_interp.m?r...

[*Eeglablist*] Question regarding use of *interpolation
function*<http://sccn.ucsd.edu/pipermail/eeglablist/2012/004797.html>
sccn.ucsd.edu/pipermail/*eeglablist*/2012/004797.html
<https://www.google.com/search?client=safari&rls=en&q=EEGLAB+function+interpolate&ie=UTF-8&oe=UTF-8#>

   -
   <http://webcache.googleusercontent.com/search?q=cache:XmTHQBXEe0UJ:sccn.ucsd.edu/pipermail/eeglablist/2012/004797.html+&cd=1&hl=en&ct=clnk&gl=us&client=safari>
   -
   <https://www.google.com/search?client=safari&rls=en&q=related:sccn.ucsd.edu/pipermail/eeglablist/2012/004797.html+EEGLAB+function+interpolate&tbo=1&sa=X&ei=Y7yCUo2rMYbMsQTfkoCABA&ved=0CDAQHzAA>
   -

Apr 14, 2012 - [*Eeglablist*] Question regarding use of *interpolation
function*. Thu Apr 5 13:58:43 PDT 2012. Previous *...*
problem *interpolating*
channels<http://sccn.ucsd.edu/pipermail/eeglablist/2011/004122.html>
Jun 21, 2011
rejecting/*interpolating* bad
channels?<http://sccn.ucsd.edu/pipermail/eeglablist/2011/003951.html>
May 11, 2011
*interpolating* bad channels (eeg_interp()
)<http://sccn.ucsd.edu/pipermail/eeglablist/2007/001945.html>
Oct 1, 2007
*interpolating* bad
electrodes<http://sccn.ucsd.edu/pipermail/eeglablist/2006/001228.html>
Jan 22, 2006
More results from
sccn.ucsd.edu<https://www.google.com/search?q=EEGLAB+function+interpolate+site:sccn.ucsd.edu&client=safari&rls=en>

The reref function on the other hand is rereferencing the data.
pop_reref <http://sccn.ucsd.edu/eeglab/allfunctions/pop_reref.html>
sccn.ucsd.edu/*eeglab*/allfunctions/pop_reref.html
<https://www.google.com/search?client=safari&rls=en&q=EEGLAB+function+interpolate&ie=UTF-8&oe=UTF-8#>

   -
   <http://webcache.googleusercontent.com/search?q=cache:GtZG0BSxxmQJ:sccn.ucsd.edu/eeglab/allfunctions/pop_reref.html+&cd=3&hl=en&ct=clnk&gl=us&client=safari>
   -
   <https://www.google.com/search?client=safari&rls=en&biw=1261&bih=888&q=related:sccn.ucsd.edu/eeglab/allfunctions/pop_reref.html+EEGLAB+reference+data&tbo=1&sa=X&ei=z7yCUqr1GoLMsQS4sICQDw&ved=0CEIQHzAC>
   -

POP_REREF, Convert an EEG dataset to average reference or to a new common
reference channel (or channels). Calls reref(). *...* Unchecked, the data
are transformed to common reference. "Re-*reference data* to *...* See
also: reref(), *eeglab*() *...*

On Thu, Nov 7, 2013 at 7:52 PM, David Kaufman <david.kaufman at gmx.de> wrote:

> Hi eeglab community,
>
> I'm currently working with eeg data which was recorded using a single
> reference electrode. I now want to reconstruct this reference by using
> reref. Later I want to be able to add this additional channel to
> improve my classifier.
>
> Currently, my call to reref looks like this:
> reref_trial = reref(trial, []);
> where trial is a 32x301 single matrix. Unfortunately, reref also
> returns a 32x301 single matrix. I was expecting to get a 1x301 matrix
> with only the reconstructed reference. Am I understanding reref wrong?
>
> Do you have any suggestions? I'm using eeglab version 12_0_2_4b.
>
> Thanks for any help
> David
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