[Eeglablist] electrode locations shifted when using headplot on EGI's GSN-HydroCel-128.sfp

[Tarik S Bel-Bahar]

Hi Ingrid,

There's a few things you may want to try if you haven't had a chance to
yet. Hope the suggestions below help.
I've worked with egi files a bit and looking forward to hearing of your
progress. As Makoto mentioned,
there may also be a new head that is available.

All the best





****************************

..I would try everything through the GUI, then use the eegh command  to
figure out which commands to use in a script
..I've usually only plotted ICA components using eeglab, but there should
be no problem appropriating the function for activity of choice,
or regressing on non-eeg variables, or showing contrasts or regions with
significant effects, all of which are published in the literature.
the best bet might be to try to contact those authors (e.g. John Allen's or
Micheal Cohen's labs)

...it's important if you have loaded the eeg data properly into eeglab and
that you can easily visualize it normally other ways.
This would be indicative of eeglab being able to work with things. For
example if you used eeglab to import a .raw export from
Netstation, that would mostly likely be different from what you have if you
loaded in a Netstation mff format file with fieldtrip.
I don't think eeglab reads in mff files specifically as of yet.

....ake sure you use the right montage (128 or 129 hydrocel) file and read
those locations in, using the GUI.
The number depends on the whether or not the reference channel is in the
EGI file that is being imported (usually .raw format)
The GUI should accept these and then close.

At this point sometime it was necessary to use the optimize head center
button as well to "spread out the electrodes" in eeglab.
Then check the 2d and 3d views of the electrodes from the channel locations
gui. See also the view channel locations.

If you have a .set EEGLAB file and components within it, then rom that
point, you should be able to plot a 3d head (at first using the gui). Try
using the suggested spline settings in the first case. try to get it
working once this way if you haven't had a chance to.




Tarik Bel-Bahar, Postdoctoral Fellow
Perception, Performance & Psychophysiology Lab
tarik.777 at duke.edu/ 919 328 9573
Div. of Brain Stimulation and Neurophysiology
Dep. of Psychiatry and Behavioral Sciences
Duke University Medical Center, Duke Clinics
Red Zone, 5th Floor, Rm. 54236
200 Trent Drive, Durham, NC 27710


On Wed, Aug 7, 2013 at 11:57 PM, Ingrid Nieuwenhuis <
ingrid.nieuwenhuis at gmail.com> wrote:

> Hello everyone,
>
> I am trying to make a beautiful 3D topoplot on the head using headplot. I
> have 128 channel EGI data, GSN-HydroCel-128.sfp layout. When I plot the
> electrode positions they are not correct, see the picture here:
> https://www.dropbox.com/s/g4b1uvwlgof63cm/headplot_GSN-HydroCel-128.jpg.
> It looks as if the net is not pulled down enough: the electrodes that
> should be on the cheeks way under the eyes are located on the eye balls,
> and also the ear in the picture is not in the ear hole of the net. All the
> electrodes are too high up.
>
> I've created the spline file with the option 'sfp' for 'filetype' as I
> read that sfp data format is supported. I used the standard EGI electrode
> location file GSN-HydroCel-128.sfp, after removing the FidNz, FidT9, FidT10
> place holders. Does any one know why this happens, and how I can fix it?
>
> I'm new to EEGlab (normally use FieldTrip). I haven't used the GUI but
> used code:
>
> % step 1 create spline file
> elocs =
> readlocs('C:\Users\Ingrid\Documents\MATLAB\FieldTrip\template\electrode\GSN-HydroCel-128.sfp',
> 'filetype', 'sfp');
> splinefile = [cur_path_MLD, 'EEGLAB_splinefiles', filesep, 'EGI_128.spl'];
> headplot('setup', elocs, splinefile);
>
> % step 2 test the electrode locations
> splinefile = [cur_path_MLD, 'EEGLAB_splinefiles', filesep, 'EGI_128.spl'];
> figure;
> headplot(rand(128,1), splinefile)
>
> Thanks a lot!
> Ingrid
>
> _______________________________________________
> 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
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sccn.ucsd.edu/pipermail/eeglablist/attachments/20130814/3797b340/attachment.html>