EEG channels import file problem

Discussions
1

Hello everyone,

I’m having some troubles when I import the EEG channel file from the Neuroscan 64 system. So the problem is that I import the channel file but some of the channels in the head are misplaced some of them outside of the head and I don’t know what could be wrong. I would appreciate some help.

I attach the channel file if anyone can help me.

Thanks in advance.

2

Hello,

What software/instrument did you use to create this file?
This order of the columns cannot be imported correctly with any of the file formats available in the menu “Import channel file”.
I could add it, but I need some more details about how this file was generated.

For now, you have to delete manually the second column (mostly “69” values) and probably the last two lines (centroid and ref).
Import it using the menu “Import channel file” with the file format “ASCII: Name, XYZ (.)”.
Then right-click on the channel file > MRI registration > Edit > Align the electrodes on the head and project the electrodes on the scalp.

Cheers,
Francois

3

Hi Francois , thanks for your help.

This file is the channel position given by this EEG “Compumedics Neuroscan inc el paso tx”. The file was originally in .dat format but to upload it there I saved it as a .txt.
I’ve done what you suggest and it works really well.

I’m sorry this is my first EEG analysis and I’d like to know how brainstorm manages the reference. I need to do a re-reference to the mastoid. Is there a way to do it?

Best Regards,

4

Actually, the correct way to import this file is to keep the file as it is (do not do the modifications I suggested before), and import it with the file format “EEG: Neuroscan (*.dat;…)”.
This should read it correctly, remove the unnecessary channels and set the channels types automatically.

By default, Brainstorm shows the EEG values the way they were saved in the file (you have to check what how those files were saved). This corresponds to the montage “All”. You can use the montage editor to create a custom montage that re-references the EEG based on the channels you want. This is presented in the EEG/Epilepsy tutorial:
http://neuroimage.usc.edu/brainstorm/Tutorials/Epilepsy

Note that this would be for signal reviewing only.
For the source modeling, Brainstorm converts everything internally to an average reference, to avoid all the reference issues.

Cheers,
Francois

5

Thank you so much Francois for your help and the information. I’m gonna read the tutorial!