When I run the command for smoothing, should I replace --cortex with  --label-trg? In other words, for ROI analysis, should we smooth only the target mask?

mri_surf2surf --hemi lh \
  --s fsaverage \
  --sval lh.gender_age.thickness.00.mgh \
  --fwhm 10 \
  --cortex \
  --tval lh.gender_age.thickness.10B.mgh


I followed the instructions from here:
https://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/GroupAnalysis 
https://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/AnatomicalROI 
https://surfer.nmr.mgh.harvard.edu/fswiki/mri_glmfit
http://freesurfer.net/fswiki/mri_surf2surf

Thank you!

Mihaela