Hello list, I would like to create a mask on fsaverage/surf/?h.pial that masks out the areas where the surface does not follow the cortex, but is just cutting across the mid line or across the brain stem. I know Freesurfer does this to maintain the surface toplogy, and I think it only does this in these two areas. Does a simple txt file with n vertices and a 0 or 1 value at each vertex exist somewhere? Has anyone on the list bothered to label this area manually and would be willing to share? thanks, mishkin