After trying some things out, the last problem that comes out is the following:
Warning: qform is already set. Nothing to do.
> In add_qform (line 69)
In load_nii_BIG_Lab (line 47)
In svreg_smooth_vol_function (line 34)
Error using imgaussfilt3
Expected Sigma to be finite.
Error in imgaussfilt3>validateSigma (line 379)
Error in imgaussfilt3>parseInputs (line 343)
Error in imgaussfilt3 (line 113)
Error in svreg_smooth_vol_function (line 46)
MATLAB:imgaussfilt3:expectedFinite
What does it mean?