On 05/02/2016 07:39 AM, maaike rive wrote:
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:
- 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 )?
Not sure. They will be different models. ICV should not change over the lifetime whereas total surface area will.
- 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...
I don't know, perhaps Marie will weigh in
- 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...
They can still reduce intersubject variance. doug
Thanks,
Maaike
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