Hi, FS experts: I'm scanning freesurfer pages about FSGD files here: http://surfer.nmr.mgh.harvard.edu/fswiki/Fsgdf4G1V and i'm interested in one contrast file(the example of Contrast 5 right-left.intercept.mtx). The original FSGD file is list as follows: GroupDescriptorFile 1 Title OSGM Class MaleRight Class MaleLeft Class FemaleRight Class FemaleLeft Variables Age Input subject1 MaleRight 30 Input subject2 MaleLeft 40 Input subject3 FemaleRight 50 Input subject4 FemaleLeft 60 The contrast file is : 0.5 -0.5 0.5 -0.5 0 0 0 0, meaning to exame the difference between Righties and Lefties regressing out the effects of gender and age. Now i consider gender as the covariate variable ('1' represents the Male and '2' represents the Female), and i setup a new FSGD file: GroupDescriptorFile 2 Title OSGM Class Right Class Left Variables Age gender Input subject1 Right 30 1 Input subject2 Left 40 2 I also want to exame the difference as suggested above, and I setup the new contrast file as :1 -1 0 0 0 0. My question is that : are the new FSGD and contrast files correct to exame the difference as suggested by original FSGD and contrast files?