[Freesurfer] question about painting SPM results onto Freesurfer

Hello everyone,

I just read the information about "paintig SPM results onto Freesurfer" ( http://surfer.nmr.mgh.harvard.edu/fswiki/SpmPainting). It shows how to painting SPM results from statistic step (ex. spmT.img) to surface space. I tested the procedure and it worked. But I don't understand what is displayed on Freesurfer surface. Are all the significant differences from SPM statistic results are displayed on this surface? or some part of t values are displayed (which part)? As cortical thickness displayed on surface, each thickness value is painted on each vertex. But here t-value image from SPM is volume image, how to paint it on surface?

Someone could give a little detailed explaination??

Thanks in advance

Karry