Hi,

 I have generated two different functional connectivity maps for two different ROI-based seeds. These maps are based on group-average of the same subjects (generated by using separate isxconcat-sess commands ), and now I want to see the difference map. To do so, I used mris_calc as below. 

> mris_calc -o diff_map/rh.ces.nii   map1/rh.ces.nii   sub   map2/rh.ces.nii

Also, to generate the rh.cesvar.nii file I used this command:
 
> mris_calc -o diff_map1/rh.cesvar.nii    map1/rh.cesvar.nii   sub   map2/rh.cesvar.nii

But then when I used the glmfit with WLS option as below:

> mri_glmfit --y rh.ces.nii --osgm --glmdir rh.ffx.osgm.wls --nii --mask ../rh.mask.nii --yffxvar rh.cesvar.nii --ffxdofdat ../ffxdof.dat --surf fsaverage rh --wls rh.cesvar.nii

 I faced an error saying: "Error: MRInormWeights: values less than or eq to 0" which I assumed is related to an error in rh.cesvar.nii file (am I right?). Would you tell me how can I fix this problem?

P.S.: please note that sequence of subjects and all MRI parameters are exactly the same between the two maps.

--
Shahin Nasr

PhD in Cognitive Neuroscience
Martinos Imaging Center, MGH
Harvard Medical School