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Dear FreeSurfer experts,
I simply do not understand the LME setup for longitudinal analyses.
Here is what I have: 3 groups each with variable longitudinal data (in terms of umber of time points and interval between timepoints). I am interested in detecting if the rates of longitudinal atrophy in each of the 3 groups and whether it is significantly different between the 3 groups.
1. My Qdec file contains: fsid, fsid_base, time, age, group, gender 2. I read in the relevant files with (output of surf2surf, lh.cortex, lh.sphere) 3. I read the Qdec file removed the first column, obtained the subject IDs, keep numerical data and get a sorted ‘M’ matrix 4. X=[intercept time grp1 time*grp1 grp2 time*grp2 grp3 time*grp3 age@timepoint1 gender] 5. After that, should I use voxel wise mass-univariate model or spatiotemporal mass-univariate model lme_mass_fit_vw or lme_mass_fit_EMinit? 6. After that I don’t understand the subsequent steps. Can you help me understand?
Any help is appreciated.
Thanks! Swati