[Freesurfer] overlay problem

hi all

i have still a problem to load an activation map on a pial surface (colin27). here are the steps followed to this end :

first i run bbregister :

bbregister --s colin27 --mov /home/mlaouche/bashr/V8.nii.gz --init-fsl --reg /home/mlaouche/bashr/regester1.dat --bold --surf pial

then i used tksurfer to see the result which seems good: tkregister2 --mov /home/mlaouche/bashr/V8.nii.gz --reg /home/mlaouche/bashr/regester1.dat --surf

i used mri_vol2surf this way :

mri_vol2surf --src /home/mlaouche/bashr/V8.nii.gz --out /home/mlaouche/makh_free/v80.mgz --srcreg /home/mlaouche/bashr/regester1.dat --hemi lh

i used again tksurfer to load first colin27 :

tksurfer -colin27 lh pial

then file/load overlay  to load v80.mgz no overlay was mapped