[Eeglablist] re-reference with EGI data

[Tarik S Bel-Bahar]

just some partial answers, hope this helps.
Please let the list know when you find out more.

FidNz = the fiducial near the nose (nation), the others are the left and
right fiducially near the ears
These are some of the basic markers for co-registration across heads/nets.
Check this image http://sccn.ucsd.edu/eeglab/dipfittut/coregister3.gif
and the eeglab wiki for more info.
These labels are often automatically detected by eeglab, and yes, they
are the three "hidden channels" at initial import.

Check the eeglab list archives for the link to ego's multiple
formats.(search EGI and/or Netstation)
Make sure you are using the right electrode locations for nets you used
(hydrocel probably).
If you export your EGI files with a reference channel, then you should use
the EGI locations
file that has the 128 + the reference channel, and so on.
Note also that the electrode location file that eeglab selects
may not be exactly the right one,
so better to feed it the one you know is right.

see below for more info

   - [Eeglablist] .ced file or list of electrode labels for 128-channel egi
   sensor net  <http://sccn.ucsd.edu/pipermail/eeglablist/2012/005041.html>
    *Tarik S Bel-Bahar*







On Fri, Aug 24, 2012 at 12:09 PM, Joshua Hartshorne
<jkhartshorne at gmail.com>wrote:

> I have EGI data recorded with a 128 electrode cap (vertex reference). I
> exported it to EEGLab and included the reference in the export (I used the
> multiple file format).
>
> EEGLab seems to recognize everything fine and includes 128 electrodes in
> the data, though when I go to "edit channel locations", I see 132 channels.
> The last one is my reference channel, labeled correctly as Cz. Though it's
> channel type is listed as "REF", no Reference is listed in the pop-up
> window (the section below the panel of "channel type") for any channel. I
> have no idea what channels 129-131 are (they are labeled FidNz, FidT9, and
> FidT10).
>
> So I want to re-reference. If I check "compute average reference", I don't
> have the option of retaining the old reference channel, which seems odd. If
> I click on the "..." button after "Add current reference channel back to
> the data", I get an error (??? Error using ==> waitfor Error while
> evaluating uicontrol Callback). From the wiki, I understand I should have
> gotten a list. Manually setting reference to "Cz" or "132" using the "edit
> channel info" window for channels 1:128 doesn't fix this problem.
>
> However, if I leave all that blank, I "successfully" re-reference to
> average reference. That is, I don't get an error, though I'm not sure how
> to determine whether it worked correctly or not.
>
> What I'd really like to do is re-reference to the average of the mastoids
> (channels 57 and 101), which would aid comparison with another dataset that
> was collected on different equipment with fewer electrodes. But the wiki
> suggests that I have to do this by going through average reference first
> (really?), so I wanted to make sure I had that much right first.
>
> In any case, I assume that if I list two electrodes in the "re-reference
> data to channel(s):" box that it will automatically compute the average of
> those two. I tried doing that (both with and without going through average
> reference), and I notice that channels 57 and 101 are *not* listed as "REF"
> in "Channel type" after doing this, while Cz is still listed as "REF",
> though "Reference" is now listed as "E57 E101".
>
> I appreciate any help.
> Josh Hartshorne
>
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