Hi Freesurfers,
For this analysis I plan to do, I want to map resting-state data in native (T1) space to the pial surface. The command I use for this is:
mri_vol2surf --src fMRI_nat.nii --regheader subjID --hemi lh --projfrac-avg 0 1 0.05 --surf pial --o fMRI_2surf.mgh
So the intention is to average the resting state data over the cortex and to map this to the pial surface. However, if I'm not mistaken the --projfrac-avg option projects along the outward pointing surface normal. Therefore, when using the pial surface, I expected that the proper call would be --projfrac-avg 0 -1 -0.05. However, this command does not run, whereas the command given above does, and yields (sensible) output. So is the command given above correct after all? And does this imply that for the pial surface, the volumetric data is actually projected along the inward pointing normals?
Best regards,
René