[Freesurfer] normal vector in gm

Hello users,

My colleagues and I are trying to create a gray matter electric conduction model where a preferable conduction direction is aligned with the normal direction induced from the pial and white surface normals.

Freesurfer reconstruction already gives pial and white matter surface normals and correspondences between them. Now I want to have the freesurfer surface normals projected on the mri volumes and interpolated for gray matter voxels (regions between the pial surface and the white surface), such that each voxel of gray matter can have a normal direction.

Is it possible to do the job with freesurfer scripts ? If so, what scripts might work for this?

Thanks in advance,

Seok