Dear freesurfer experts,I have a question regarding correction of cortical measures or global measures (ICV, total surface area). As I understand from literature and the freesurfer wiki, a model for thickness should not be corrected for ICV (since thickness does not scale with total brain volume), but surface area should be corrected since is does scale with total brain volume. Three questions:1. should I use ICV or should I use total surface area (TSA) as covariate in the model to correct surface area (by the way, average ICV and TSA do not differ between the groups to compare )?2. does lGI also need correction? does it scale with volume? If so, do I need to correct for ICV or for TSA? Usually I see no correction but some do use ICV...3. even if the average of certain measures (like ICV/TSA, or gender, or age) does not differ between groups, should they be added to the model? If I do not correct for gender, for example, my results change and most papers do use age and gender as covariates if they compare groups despite a lack of differences between groups... Thanks,Maaike