Hi everyone,
From FreeSurfer manual and discussion forum, I found that volume and LGI
can be correlated using mri_glmfit command with -pvr flag.
For that, my fsgd file has age, gender as covariates and the file is as following:
GroupDescriptorFile 1
Class Male
Class Female
Variables Age
Input zerek1 Male 21
Input zerek2 Male 25
etc.
My concern is:
To run mri_glmfit command, I am not sure how to define my contrast matrix if I am interested in removing the effect of age and sex.
1st option I tried is: 0 0.5 0.5 0 1
Here, I think first 0 regresses out age, 0.5 0.5 should be averaging over males and females and last 0 1 correlates between volume and LGI. But this looks like it is not giving me correct correlations maps, although there is no error.
2nd option I tried is: 0 0 0 0 1
This looks like its working and maps look correct to me but I want to make sure this is the correct contrast matrix and I am not sure how this matrix is regressing out age and gender or 1st option is correct contrast matrix?
Thank you so much !
Best,
Sahil