Hey
I can't correctly import my channels location from EEGlab to Brainstorm.
In my EEGlab .ced, I have:
and when I look at Channel file in brainstorme, I have:
Same issue when I try with EEGlab .xyz file.
I don't understand why.
I modified a default cap with 64 channels (Easycap) to get a 32 channels cap. But I don't know if it is a correct solution. My cap is a gtec cap. What do you think?
If you wonder why you can't read the same coordinates in your .ced file and in the channel file editor in Brainstorm, this is normal. Brainstorm rewrites all the input data following its own conventions. All the 3D coordinates are converted to SCS/CTF coordinates: https://neuroimage.usc.edu/brainstorm/CoordinateSystems#Subject_Coordinate_System_.28SCS_.2F_CTF.29
There is possibly a problem on top of it, which is what Brainstorm thinks is in input.
The file formats .ced and .xyz do not describe what they contain. Brainstorm considers that .ced files contain non-realistic spherical coordinates (used only for producing 2D circle plots in EEGLAB), and multiplies the coordinates by an average head radius. The distances in the .xyz files are not modified, but the axes X and Y are exchanged and filpped.
https://github.com/brainstorm-tools/brainstorm3/blob/master/toolbox/io/import_channel.m#L186
These operations correspond to the example files our users submitted, and probably do not fit all the possible configurations the file formats offer. Both would result in incorrect 3D positions in Brainstorm.
As you are importing these positions on an Brainstorm template, you will have to adjust the positions of the electrodes on the head surface no matter which file format you use, so it doesn't matter much how far you are from the correct position.
Right-click on the channel file > MRI registration > Edit, adjust the position and size of the electrode cap (read the tooltip of the various buttons in the toolbar) and when it looks almost good, project the electrode on the head surface. If needed, you can move each electrode on the surface.
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