[Eeglablist] Re-Reference

[Baris Demiral]

Since I use biosig to import bdf files, and biosemi bdf needs a reference
while importing (to preserve some power), I am fine as soon as the biosig
function works fine.

What I can suggest to other people is the following:

If you have already recorded your eeg with a reference electrode in the
montage, and you just need to re-reference the data so that "the eeg data
will have the reference to the average of the two electrodes", you can use
David Groppe's script.

In his function there is a line:

data_avg=data_in2-repmat(data_in2(mastoid_id,:),size(data_in,1),1)/2;

Since in the input file of this script, the first reference electrode
would have a value of "0", the last piece of code at the end of
data_avg above (divided by 2) will mean to take the half of the value
of the new reference electrode row and subtract it from all other data
matrix without explicitly defining the first reference (because its
value would be 0 any ways). This will mean to "re-referencing the data
to the mean/average of the two electrodes".

If you had a grand average reference or similar montage in which you
did not have an electrode with a value 0 during the recording, and you
need to reference the data directly to one electrode: you can use the
same script and just take out the "divided by 2" part. This will
reference everything to the electrode you define. Is this right David?

Baris

On Sat, Mar 12, 2011 at 3:22 AM, Tom Campbell <tom_campbell75 at hotmail.com>wrote:

>
> Hi, Here's a bug report.
>
>
>
> https://sccn.ucsd.edu/eeglab/bugzilla/show_bug.cgi?id=1001
>
> I'd be interest what you make of it.
>
> Best regards,
>
> Tom.
>
>
>
> > From: oricon at umich.edu
> > Date: Wed, 9 Mar 2011 12:07:17 -0500
> > To: demiral.007 at googlemail.com
> > CC: eeglablist at sccn.ucsd.edu
> > Subject: Re: [Eeglablist] Re-Reference
>
> >
> > Hi Baris, I wasn't aware there was a bug in pop_reref (do you have the
> > post about this? - I searched through the last several years and
> > didn't see anything). I don't actually use pop-reref for my data, I
> > use Biosemi, so I set the average mastoid reference when I read in my
> > data with pop_biosig. I have used pop_reref to then go to an average
> > reference, and I've never experienced any problems with the
> > re-referencing.
> >
> > -Joe
> >
> > On Wed, Mar 9, 2011 at 3:25 AM, Baris Demiral
> > <demiral.007 at googlemail.com> wrote:
> > > A while ago there was a bug related to the pop_re-reference in EEGLAB
> and it
> > > was not working at all. I wonder this is fixed now. I have been
> importing my
> > > files with M1 reference  (in my montage 65), and then use David G's
> script
> > > to re-reference it to the mean of the M1 and M2 (66).
> > > Joseph, are you sure EEG = pop_reref( EEG, [65 66] is working properly.
> If
> > > so which version of eeglab are you using?
> > > best,
> > > Baris
> > > On Tue, Mar 8, 2011 at 5:39 PM, Joseph Orr <oricon at umich.edu> wrote:
> > >>
> > >> If you're using the pop_reref GUI then just put the two channel
> > >> numbers in the "re-rereference data to channel(s):" box separated by a
> > >> space (e.g. 65 66).
> > >>
> > >> If you're using the command-line: EEG = pop_reref( EEG, [65 66] ).
> > >>
> > >> --
> > >> Joseph Orr
> > >> PhD Candidate
> > >> University of Michigan
> > >> Department of Psychology
> > >> Cognition & Cognitive Neuroscience Area
> > >> 4422 East Hall
> > >> 530 Church Street
> > >> Ann Arbor, MI 48109-1043
> > >> Email: oricon at umich.edu
> > >> http://sitemaker.umich.edu/josephorr/home
> > >>
> > >> On Mon, Mar 7, 2011 at 6:58 AM,  <aarjona at us.es> wrote:
> > >> > Hello.
> > >> >
> > >> > I´m trying to reference to M1 and M2, but in the pop of eeglab only
> can
> > >> > appear one of them (reference     M1).
> > >> >
> > >> > How can I reference to both channels?
> > >> >
> > >> > Thanks so much
> > >> >
> > >> > _______________________________________________
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> > >>
> > >> _______________________________________________
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> > >
> > >
> > >
> > > --
> > > SB Demiral, PhD.
> > > Department of Psychology
> > > 7 George Square
> > > The University of Edinburgh
> > > Edinburgh, EH8 9JZ
> > > UK
> > > Phone: +44 (0131) 6503063
> > >
> >
> >
> >
> > --
> > Joseph Orr
> > PhD Candidate
> > University of Michigan
> > Department of Psychology
> > Cognition & Cognitive Neuroscience Area
> > 4422 East Hall
> > 530 Church Street
> > Ann Arbor, MI 48109-1043
> > Email: oricon at umich.edu
> > http://sitemaker.umich.edu/josephorr/home
> >
> > _______________________________________________
> > 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
> >
>
>


-- 
SB Demiral, PhD.
Department of Psychology
7 George Square
The University of Edinburgh
Edinburgh, EH8 9JZ
UK
Phone: +44 (0131) 6503063
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