Thank you very much for your quick response Francois.
The scouts are defined on the default anatomy and comes from FreeSurfer/HCP. The default anatomy I'm using is a fsaverage on which I imported the HCP-MM atlas from Glasser et al., 2016 (https://www.nature.com/articles/nature18933). Thus everything (registered spheres etc..) are available. However, I don't have the atlas in the individual surfaces.
As for the interpolation matrix, for another project where I was using Fieldtrip, I computed it using the same approach as in the Matti's MNE manual (morphing) and used it to switch from individual to group space by matrix multiplication. Is it computed differently in Brainstorm? How I'm supposed to project my results for a group analysis?
Thanks !
D.