[Freesurfer] Computing relative cortical measures maps instead of absolute cortical measures maps

External Email - Use Caution

Hi,

I am referring to a paper of Vuoksimaa et al. 2016. The authors used relative instead of absolute cortical measures (cortical thickness and surface area) to compute individual vertex-cognitive ability correlations throughout the cortex.

To compute individual relative cortical thickness and surface area maps of each individual subjects, the authors divided the surface area value at each vertex by the total surface area (sum across all vertices for each subject) and subtracted the mean cortical thickness value (for each subject) from the thickness at each vertex.

I would like to use the same approach (relative CT and SA maps instead of absolute maps) for one of the projects of our lab. In the Freesurfer mailing list, I found that the command "fscalc" can be used for simple mathematical transformations of mgh files.

Therefore my question: Would it be correct to use “fscalc” with the option “sub” resp “div” to compute these relative cortical measures maps for each of my subjects?

Thank you for helping me with this question

Angela