oh, if the overlay vector is already computed on the downsampled surface then you are all set (it doesn't just downsample, but also maps to fsaverage)

cheers Bruce On Tue, 20 Dec 2011, Ecker, Christine wrote:

Many thanks for your reply.

Unfortunately the option -sval didn't work and it is still using the old sphere.reg file.

I was however wondering whether mri_surf2surf already sorts vertices and hence makes them comparable. For instance, is vertex 1 on the resampled surface the closest match to vertex 1 on the target surface? In that case, I would not even have to map data back to fsaverage6.

Best, Christine

On 20/12/2011 15:53, "Bruce Fischl" fischl@nmr.mgh.harvard.edu wrote:

...

Hi Christine

I think you do it the same way, just using -sval instead of -sval-xyz (since you are mapping a scalar field instead of the coordinates).

cheeers Bruce On Tue, 20 Dec 2011, Ecker, Christine wrote:

...

Dear FreeSurfer Experts,

I would like to down-sample the pial surface of individual subjects to have the same number of vertices as fsaverage6. I have done so using:

mri_surf2surf --hemi lh --srcsubject 'subjectID' --sval-xyz pial --trgsubject fsaverage6 --trgicoorder 6 --trgsurfval 'outputfilename'

This worked well and the pial output surface has 40962 vertices. I now have an overlay vector, which was computed on the down-sampled pial surface, which I would like to map back to fsaverage6 in order to perform a group comparison.

Please could you advise on how to do this as all scripts I am aware of (e.g. mris_preproc) use sphere.reg, which has ~150000 vertices.

Many thanks, Christine

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