[Eeglablist] Should Average Reference Include Eye Channels?

[Tarik S Bel-Bahar]

You will get eyeblink IC s even with eye channel removal.

You should get near-eqivalent solutions whether or not you include eye
channels.

Some groups isolate and use only the IC of interest, either focusing on IC
activation, or backprojecting only that single IC.

Rereferencing without eye channels will still include some inevitable eye
activity picked up by other frontal channels.

Comparing several rereferencing schemes, and comparing your results across
these schemes, will probably be most educative.

Whole head coverage in current systems is not true whole head coverage.
Systems that

Please be sure to post your final solution when you can.
On Feb 10, 2012 12:15 PM, "Matthew Stief" <ms2272 at cornell.edu> wrote:

> Thanks to all the responses so far!
>
> I am using a 128 channel BioSemi ActiveTwo system, so the eye channels
> are not bipolar.  I imported with a reference to the linked mastoids,
> and would like to rereference to the average.  My worry was the one
> raised by Simon-Shlomo below, which is whether or not the extra
> artifactual activity in the eye channels would contaminate the other
> channels.
>
> This possibility, I gather, is balanced against the goal of having as
> many electrodes covering the head as completely as possible to match
> the assumption of average referencing as closely as possible, as Robin
> mentioned.
>
> Makoto, what is your opinion on these two issues?  I am planning on
> running ICA, not for artifact detection but to isolate the P1, and was
> planning on including the eye channels to better separate out those
> those artifactual sources.  And just to be sure I understand you, you
> are saying that if I rereference to the average of only the 128 scalp
> electrodes, and then run ICA on all 132 electrodes, that ICA will
> average reference the data to all 132 electrodes again?  I believe I
> remember reading that referencing after epoching and baseline removal
> is erroneous, so how is that possible?
>
>
>
> On Thu, Feb 9, 2012 at 5:15 PM, Simon-Shlomo Poil
> <poil.simonshlomo at gmail.com> wrote:
> > Dear Matthew,
> >
> > I would recommend you not to include your eye channels in your average
> > reference.  If you still have eye-blinks in these channels, they will
> > just contaminate your other channels.
> >
> > (If you already removed your eye-blinks using ICA, it's probably ok to
> > include them in the average reference.)
> >
> > -Simon-Shlomo Poil
> >
> >
> > 2012/2/9 Matthew Stief <ms2272 at cornell.edu>:
> >> Greetings!
> >>
> >> I am using a 128 channel BioSemi active system, and am importing my
> >> files using the average mastoids as the reference.  I would like to
> >> rereference to the average, but am unsure if I should use my four eye
> >> electrodes.  I read in the archives that this shouldn't be done for
> >> eye electrodes that do not have the same reference as the scalp
> >> electrodes, but given that in this case they do is there any reason
> >> not to do it?
> >>
> >> --
> >> _________________________________________________________________
> >> Matthew Stief
> >> Human Development | Sex & Gender Lab | Cornell University
> >> http://www.human.cornell.edu/HD/sexgender
> >>
> >>
> >> Heterosexuality isn't normal, it's just common.
> >> -Dorothy Parker
> >> _______________________________________________
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> >
> >
> > --
> > Simon-Shlomo Poil
> >
> > Webpage: http://www.poil.dk/s/ and http://www.nbtwiki.net
>
>
>
> --
> _________________________________________________________________
> Matthew Stief
> Human Development | Sex & Gender Lab | Cornell University
> http://www.human.cornell.edu/HD/sexgender
>
>
> Heterosexuality isn't normal, it's just common.
> -Dorothy Parker
>
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