I am analysing some EEG data that was collected on an ANT waveguard 128 cap, according to the five percent electrode system.
I want to use the MNI template for the cortex in Brainstorm, but there is only one default cap from ANT, and it is with an equidistant hexagonal layout, which is not the same (https://www.ant-neuro.com/products/waveguard/electrode-layouts).
What should I do to use my cap? Is there anyone that has the 3D positions of this cap (I don't know where to find them or how to build them...)?
Unfortunately, we don't have default electrodes positions in MNI space for these EEG caps.
Could you contact the ANT customer support to ask them if they could share this with you?
If you can get a file with 3D positions (in any coordinate system), please send it to me, I will add it to the Brainstorm distribution.
Otherwise, you can use Brainstorm to place all the electrodes manually on the surface of the head, maybe starting from a template (right-click on the channel file > MRI registration > Edit)...
The ANT and the Cartool file are not representing the same cap:
the ANT Xensor file looks like a real digitization, which is not symmetric and presents significant localization errors.
the Cartool seems more artificial, and looks better as a template, but I'm not sure it has exactly the same head proportions.
Deciding on what is an acceptable set of default 3D positions is difficult for me, not having even a photo on how the cap looks on someone's head.
I added 2 versions of these positions in the Brainstorm distribution:
In Default EEG cap > Not Aligned: The ANT Xensor realistic digitized positions, not projected on the head surface: it is up to the user to align it and project it on the scalp
In Default EEG cap > ICBM152/Colin27: The Cartool file realigned and projected on the MNI ICBM152 head surface.
If you think this is not a satisfying result (eg. the cap goes too low in the neck, not low enough on the nasion, the ears do not seem positioned correctly...), you could try redoing it yourself:
Create a new subject, using the the default anatomy (MNI ICBM152)
Create a new folder, import one of the two channel files (you need to select the appropriate file format)
Right-click on the channel file > MRI registration > Edit
Start with rigid transformations (rotations + translations of the full cap), then resize to fit better the size of the head, project the electrodes on the surface, and finally move the electrodes one by one on the head surface. (read the tooltips of the buttons in the toolbar for help)
Save the modification, upload the resulting channel file file somewhere and post the download link here
Sorry I should've shared here before.
I contacted them and they said that they didn't have the 3D positions for the 128 system. They could only give me an example of a digitalization from one subject if I wanted... But it is just one real digitization, can have errors and so on, so it shouldn't be used to create the default positions
A single subject digitization aligned on the template is maybe better than nothing at all...
This just needs to be done (or at least validated) by someone who actually knows what the cap looks like on a human head.
The Cartool file seems like a real template though. Was it reworked by Denis or someone else at HUG to be symmetric like this?
Dear Francois,
Do we have 3D position of for ANT waveguard touch dry electrode cap (64 channels) with an equidistant hexagonal layout. We intend to acquire EEG data using the cap. Or else, is there any default cap from ANT waveguard that I can use.
Best,
Umesh
There is currently no 64-electrode waveguard cap in the defaults distributed in Brainstorm. This is something you can look at yourself in the list of available EEG positions.
I don't know if the positions of the 64 caps are subsets of the 128 or 256 caps.
If they are, and if the electrodes names are consistent across caps, you might be able to use directly the positions of the 128 cap with your 64-electrode recordings (with the menu Add EEG positions).
Otherwise, the beginning of this discussion thread is applicable.
Does anyone know how the ANT/Duke equidistant hexagonal layout matches the international 10-5 layout system?
I am currently using an ANT Waveguard original cap with 32 channels, and I would like to build a file containing the 3D positions of my 32 electrodes (according to the international 10-10 layout system) from the ANT Waveguard 128 channel file stored in the defaults distributed in Brainstorm (which corresponds to the ANT/Duke layout system).
Thanks!
Hello everyone, dear François,
Please find attached a .mat file containing the ANT Neuro Waveguard original headset 33 electrodes (32 channels + the REF) 3D positions. The electrodes are labeled accordingly with the international 10-10 nomenclature. The REF corresponds to the CPz electrode.
I hope this helps. Please do not hesitate to contact me if you find any issues.
Best,
Valentin
