The --fwhm on mri_vol2surf smooths in the volume, not the surface.

func2sph-sess calls mri_vol2surf and also smooths in the volume.

sphsmooth-sess calls mri_surf2surf and smooths on the surface (uses mri_surf2surf).

There are some important (and poorly understood) implications in performing smoothing in the volume or on the surface. In theory, you would never want to smooth in the volume when running a surface-based analysis. In practice, a little bit (~5mm) of smoothing can help as it can be hard to make the surface perfectly sample the functional.

Additional smoothing between the 1st and 2nd level (both in the vol and on the surface) can also help improve the intersubject registration.

doug

On Thu, 14 Dec 2006, Cameron Ellis wrote:

Hi, I am trying to smooth fucntional data on the spherical surface and I see that there are a few options for how this can be done and was wondering if anyone has any suggestions for an optimum smoothing technique. I see one option is implementing smoothing as a tag in mri_vol2surf but I also see sphsmooth-sess as another option. Does mri_vol2surf call sphsmooth-sess and work off the same algorithm? If not, when would I use sphsmooth? I also see that func2sph offers the option of smoothing before resampling. When would this be a good idea? Thanks, Cameron _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer