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.
Another question I have is how can I create contrasts to control etiv between groups, like 2x2 comparison.
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