Electrode position alignment problem

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1

Hello there,

I am new in Brainstorm and would like to ask a question to experienced ones. I imported my MRI into Brainstorm and completed the segmentation using CAT12. Then I followed the tutorials to import channel locations.

I imported the already pre-processed data from EEGLAB. I am using a Locallite channel locations coordinate system. In order to align the electrodes with individualized MRI I right clicked the 'EEGLAB channels' added EEG positions file in '.cvs' file format.

I ended up with a completely incorrect electrode positioning. You may see the image of it.

PS: I am using a custom cap with additional cerebellar electrodes at the back of the head.

I'd appreciate any help.

MRI_EEG
MRI_EEG882×974 72 KB

Thanks in advance!
Andac Topkan
University of Leipzig

2

Does your file contain positions for the Nasion, LPA and RPA?
This are used by Brainstorm to automatically align with the same points in the MRI.

If it does not, you could use the option Refine registration using head points in the figure that appears at right-clicking on the channel file > MRI registration > Edit.
An example here: https://neuroimage.usc.edu/brainstorm/Tutorials/Epilepsy#Register_electrodes_with_MRI

3

My file contain positions for fiducials, but ther are named as 'Left Tragus', 'Right Tragus', 'nasion'. Is the problem naming? Does the software automatically use fiducials?

4

For the moment it will not, these are the expected names for fiducials:

  • Nasion: {'nas', 'nasion', 'nz', 'fidnas', 'fidnz', 'n'}
  • Left ear: {'lpa', 'pal', 'og', 'left', 'fidt9', 'leftear', 'l'}
  • Right ear: {'rpa', 'par', 'od', 'right', 'fidt10', 'rightear', 'r'}

It would be good idea to add the your fiducial names as well.

Could you share your file with channel location to test over here?
You can share a download link either in this post or a direct message to me.

5

Thank you @Andac for the example files:

The support for files from Localite with names including spaces is now added in Brainstorm. As well as the alternative names for the left ear and right ear fiducials: 'left tragus' and 'right tragus'. Both in commit: d53580a

Update your Brainstorm instance to get this feature

When importing the channel file, select the option EEG: Localite (*.csv)