Dear FreeSurfer Group,
Sorry for interrupting.
I am Hui Li, a researcher fron Beijing, China, interesting in sMRI of mind disorder. Recently, I am working on some data about schizophrenia. I compared the patients and healthy controls, and found that the main difference between these two groups is the index of "meancurv". So I searched online for the papers described "meancurv" of using FreeSurfer package, however, most of the papers reported an index---gyrificaiton, some of the gyrificaiton was calculated from "absoult mean curvatura", for example articles from Dr. Luders (A curvature-based approach to estimate local gyrification on the cortical surface, NeuroImage, 2006, 29, 1224). Then I looked for how to calculate "meancurv" in FreeSurfer, I found that "The curvature in general is measured as 1/r, where r is the radius of an inscribed circle. Since mean curvature is the average of the two principal curvatures it has the units of 1/mm. The Gaussian curvature is the product of them, so it is 1/mm^2". I am confused about these two concepts of "mean curvatura", could you help me to understand the "mean curvatura" in FreeSurfer? What is the biological meaning of this index, does it share the same anatomical meaning with Dr. Luders'? Could I use "mean curvatura" from FreeSurfer represent Gyrification Index?
Thanks all of you so much.
Hui Li