[Eeglablist] Help with EEG channel location import, channel numbers incorrect

[Clement Lee]

Hi Maria,

I don't think problem 2 can be avoided. For problem 1 though, is your
EEG.data being shuffled, or are your EEG.chanlocs.labels? Does the captrack
.sfp contain the same channel labels as your EEG.chanlocs.labels before
importing channel locations? If you know these things and your data is
consistently collected in the same way, you can add any corrections in a
preprocessing script.

Best,
Clement Lee
Applications Programmer
Swartz Center for Computational Neuroscience
Institute for Neural Computation, UC San Diego
858-822-7535


On Fri, Sep 27, 2019 at 1:03 AM Maria Fini <mfini at asu.edu> wrote:

> Hello Community,
> I am new to eeglab and having some trouble with importing my recorded
> electrode locations.
> I recorded 64 channels of data using the brainvision EEG recording system,
> with electrodes in the standard 10-20 locations, except 1 electrode, which
> I removed to do ultrasound stimulation, and placed on the chest to record
> HR.
> Electrode montage matches that of the template file
> ('[eeglabPath]/plugins/dipfit2.3/standard_BEM/elec/standard_1005.elc')
> with the reference at the left mastoid and the ground front and center on
> the cap.
>
> I recorded each subjects' electrode locations using the brainvision
> captrack system.
> When I go into the gui edit>channel locations> then click 'Read locations'
> to bring in the.spf file, the 3d plot of the electrode locations looks
> correct, but I am running into a couple of problems: (an pointers would be
> greatly appreciated)!
>
> 1) Main problem I'm having is that the channel locations look correct in
> space, but are registering with different channel numbers than the default
> locations, which I am 99% sure is how my data was recorded. Ie electrode
> Fp1 in the default template, and I believe also in my recording, is
> registered as channel 1 in the EEG data, but when I load in my recorded
> locations, it shows up as channel 43, so the data and electrode assignments
> are getting shuffled into wrong positions in the eeg data matrix (see
> attached photo 3: template locations on the right, left is data after .spf
> channel location file loaded). I think the program is assigning them
> numbers 1-64 based on what order the electrodes were detected by the cap
> track system, because usually the algorithm starts by the left ear. Yet,
> the locations in 3d space are correct.
>
> 2) Secondary problem is that the electrode which I removed from the cap for
> the ultrasound and used to record the heart rate, was also removed from the
> captrack file. I don't really want this electrode included in the global
> scalp calculations because it was used to record HR, not EEG. It seems I
> have to manually enter it back in to prevent an error in the system from
> having less electrode locations than recorded channels. I can manually do
> this using the coordinates of the reference, but it's a pain.  This channel
> seems to get rejected in cleanline, so I guess it isn't too much of a
> problem.
>
>
>  I suppose I could just go forward on my data processing with the default
> locations, but I figured since I recorded the actual electrode locations, I
> might as well use them. Any suggestions on how to still use the recorded
> locations, but not screw up the channel numbers would be wonderful!
> Thanks for your time.
>
>
> --
> Maria Fini
> Arizona State University
> Tyler Neuroperformance Lab, Dept. of Biomedical Engineering
> PhD Student
> *703.989.9650*
> *mfini at asu.edu <mfini at asu.edu>*
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