Hi Wen,
Brain volume has a good relationship with the overall surface area measured
in native space (so, irrespective to any kind of interpolation). We found
an R^2 of 0.856, which is higher even than the correlation of brain volume
with gray matter volume as measured via VBM-like methods.
However, even if the relationship between these measurements were poor,
include brain volume as a covariate hardly hurts the model, unless you have
only few degrees of freedom (say, a tiny number of subjects).
Another thing, and perhaps better, is to consider using global surface area
instead of brain volume as a covariate for a study of surface area, to
remove global and focus only on local effects.
All the best,
Anderson
2013/6/24 wen.zhang55
> Dear Freesurfer,
>
> I have checked the mail list, none could answer my problem.
> I added up the value of all vertxes in the .area or .area.pial files, find
> that brain size did not contribute much to that vertex-sum. However, some
> experiment used total brain volume as a regreesion coefficient to remove
> brain size effect. In these case, with the comparison of surface area in
> vertex-to-vertex, is it proper to use the above vertex-sum as the
> regression coefficient to remove different brain size?
> Thank you very much!
>
> Cowen
>
> 2013-06-24
>
>
>
> wen.zhang55
>
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