Hi Freesurfer Experts,

   I am comparing a control group and 2 patient groups (HC vs Group1, HC vs Group2, Group1 vs Group2).  I am interested in seeing what is the most appropriate covariate to use for both a cortical thickness analysis and LGI analysis.  I do not expect major changes in brain shape etc, and at most maybe some more cortical atrophy in one of the groups)

I have seen several papers using ICV for cortical thickness analyses, however I am not sure if this makes the most sense.  Does ICV really scale with thickness as a global measure to account for brain differences?  To me something like left mean thickness and right mean thickness may make more sense, however, I am new to CT analyses and would like to get your feedback.

Along with CT, I was interested in what covariate makes most sense in an LGI analysis.  Since LGI may change depending on the location within the brain, does a global measure such as total surface area (or other measure) make sense?  Is there a suggested covariate to use for this type of analysis?

Are there any publications from your group regarind this issue?

Thanks,

Ajay