When I import in Brainstorm a fif file, after editing the channel file, I obtain a table with four locations, four orientations and 1 weight. Could you tell me more at which points correspond these four locations/orientations ?
If I use these data to match in matlab the MEG sensors on cortex mesh, it well works.
But if I export to file the channel file, I obtain a xyz file which not give the same information in term of sensors coordinates (and not the same coordinates range). And if I use this xyz file to match the sensors on the cortex mesh in matlab, the result is totally false.
Do you have more explanations about this ? What is the transformation between the xyz file and the native channel location table ?
Thanks
Etienne
Hi Etienne,
Each MEG sensor is described using several integration points, to represent better the spatial extension of the coil. The way each sensor type is represented is described in the file “brainstorm3/toolbox/io/coil_def.dat”, written by Matti Hamalainen.
This “export” menu on the channel file is only here to export EEG electrodes positions in Cartool format (more options coming soon…). It does not make sense to export MEG sensor descriptions to a simple ASCII file of that kind.
To transfer the channel file:
- to a different subject or condition in the same protocol: just use the copy/paste operations in the database explorer
- to a different protocol / computer: copy the channel_…mat file
With EEG electrodes, if you do Export to Cartool, and then Import from Cartool (make sure you are using the “Cartool XYZ” file filter), you are going to get the same results before and after.
Hope that answers all your questions
Cheers,
Francois