Hi Doug, Thanks for the follow up. Do you recommend using a covariate such as mean thickness or is a covariate not necessary for cortical thickness analysis?

Thanks, Ajay

On Thu, Sep 8, 2016 at 2:00 PM, Ajay Kurani dr.ajay.kurani@gmail.com wrote:

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