This is a question about the biology. I.e., when you include mean thickness as a covariate, you are then measuring the difference between groups subtracting out the mean thickness of each individual. By using a hemisphere specific value, you might introduce (or remove) cross-hemispheric effects.
On 6/8/2019 11:33 PM, Pedro Rosa wrote:
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Dear all, I read previous threads on the list concerning the use of 'total measures' (e.g., mean thickness, total brain volune, total area) as covariates in FreeSurfer's group analysis Given that FreeSurfer analyses brain hemispheres separately, would it make more sense to use hemispheric values (i.e., lh total area in the lh area analysis and rh total area in rh area analysis) than the mean cortical value (e.g., mean between lh and rh total area in both lh and rh analyses)? Best, Pedro.
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