[Freesurfer] very high/low values in the mri_glmfit results

Hi FreeSurfers,

I'm running a group-level analysis of the fMRI data (beta-maps of individual subjects normalized onto fsaverage). One example would be like:

mri_glmfit --y grouprfx/lh.con_0001.norm.mgh --surf fsaverage lh \ --glmdir grouprfx/lh.con_0001.osgm --osgm

I understand that this is simply performing a one-sample t-test on each vertex. However, the resulting image (lh.con_0001.osgm/osgm/sig.mgh) contains some values that are extremely high or low (1e11 or 1e-11). I guess this is a representation of Inf and -Inf, but this is strange because when I run one-sample t-test manually in Matlab, the resulting t-values should be within an interpretable range. I have many subjects (close to 250), but I don't think that should be the reason.

Any clues on why this is happening and how to resolve it?

Thanks in advance as always!

Joon