Group average with cortical source grid

Discussions
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1

Hi Brainstorm !

I would like to know if it is possible to use a cortically-constrained source grid for all subjects with deformation from ICBM152? I already know that it’s possible to use the same source grid (with deformation from subject to subject) using a volumetric source grid, but what about cortical source grid?
If I compute (for one subject) a forward model restricted to the cortex, I will obtain a Gain matrix of dimension : N_(chan) x (3*15000) (in the case of 15000 vertices). If I do that for all subjects, does the index of each source is related to the same anatomical region for every subject? So, can I just (at the end of my calculation), directly average my results to obtain my group analysis?

I hope the question if clear enough, otherwise I can explain it differently.

Thanks a lot

2

If you compute a deformation to an MNI template for all your subjects (https://neuroimage.usc.edu/brainstorm/Tutorials/TutWarping#Warping_the_template_anatomy), the cortex topology is the same for all the subjects. A given vertex index corresponds to the same brain region for all the subjects.
Therefore you do not have any additional registration step to go through, you should be able to average/compare directly your results across subjects.