Importing captrak files

Discussions
21

Hi Raymundo,

I came across another instance that I wanted to ask you about:

For some of our participants, we could not record CapTrak data due to mechanical issues. In these instances, we use the channel file from the .set file, which has the updated BrainVision standard 96-channel cap layout.
On first import, I refined the channel locations to the digitized head points, resulting in the following registration:

head point registration
head point registration1920×1523 52.4 KB

In trying to troubleshoot this issue, I re-imported the data without refining the channel locations to the digitized head points of this person's MRI, leading to this registration (which I think is better than the first one):

no head point registration
no head point registration1682×1752 56.8 KB

If I refined the channel locations to digitized head points for other subjects that don't have CapTrak data, but did not do so here, is this an issue? I'm learning Brainstorm and want to ensure changing this setting in this way doesn't affect reproducibility in methods between subjects.

Thank you,
Adam

22

Additionally, another question came up.
I just discovered the "Warp default anatomy to fit these points" function.
If I have CapTrak data, should I be using this function to warp the ICBM 152 2023b brain to fit the electrode layout (thus adjusting the standard anatomy to the person's head, measured by the electrode positions), or should I only project the CapTrak electrodes to the surface of the default brain's scalp without warping?

In the warping tutorial: https://neuroimage.usc.edu/brainstorm/Tutorials/TutWarping#Edit_the_initial_MRI.2FMEG_registration, it says that, "The grey surface is the template head surface and the green points represent the head points we digitized from the head of our subject" which confuses me because I thought that the head points that were present around the default anatomy were not subject specific, and these should not be used to make the default anatomy subject-specific.

Thank you again for the guidance.
Adam