On 2/19/2022 6:10 PM, fernanda rohrsetzer wrote:

        External Email - Use Caution        

Hi guys, 
I'm a beginner in Freesurfer and I want to perform an analysis of the difference between 3 groups in cortical thickness,volume and area having age, mean thickness and etiv as covariate.
my design matrix for 3 groups 
   comparison as "1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 (LR-HR)
                             1 0 -1 0 0 0 0 0 0 0 0 0 0 0 0 (LR-MDD)
                              0 1 -1 0 0 0 0 0 0 0 0 0 0 0 0 (HR-MDD)

If possible, I would like to know how my contrasts change when I wish to test the change in thickness with age, after removing the group effects.
It is just move the non-zero values in the contrast to the age columns, like
0 0 0    1 -1 0    0 0 0 0 0 0 0 0 0
Another question I have is how can I create contrasts to control etiv between groups, like 2x2 comparison.
I don't understand.
btw, you should normalize your covariates (ie, remove the mean, divide by the sqrt(sum(squares)))
I'm sorry if I was not clear...
thanks
Fernanda
my FSGD file is
GroupDescriptorFile 1
Title MyStudy
Class LR
Class HR
Class MDD 
Variables age meanThick totalarea eTIV
Input Sub001  LR  14.3 1350519.71 1954527.71 1552459.71
Input Sub002  MDD 15.7 1558515.86 1689767.98 1809809.87


_______________________________________________
Freesurfer mailing list
Freesurfer@nmr.mgh.harvard.edu
https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer