Dear Doug and FreeSurfer experts,

Thnak you so much for all your lasts responses!.

I did ran succesfully all the pre-processing for the interhemispheric comparisons on FS. Now I have a couple questions:

given the command for interhemispheric comparisons:
mri_glmfit --y lh.lh-rh.thickness.sm05.mgh --glmdir glm.lh.lh-rh.thickness.sm05 --osgm --surf fsaverage_sym lh;

A) This read all subjects to construct X and C as one-sample group mean, this means that as result I get the difference across hemispheres and across my subjects in a population, right?

B) But, what if I have two groups? controls and patients, I'm wondering if is it possible to examine regional differences of thickness asymmetries between those two groups? or more?

C) If I want to examine effects of group or sex, while controlling for age and other factors how do I introduce them into the glm model? If so, do I set the contrasts as normally for mri_glmfit? I mean as any other thickness study? or there is any other thing that I should do?

The command for multiple comparisons correction is:
mri_glmfit-sim --glmdir glm.lh.lh-rh.thickness.sm05 --cwpvalthresh .5 --cache 2 abs
Which performs only cluster-wise corrections,

D) is there any other way to correct for multiple comparisons, something like permutation tests or anything else?


Many thanks in advanced,
Gabriel