Yes, it is. It is confusing when you talk about area and volume since these are not point measures like thickness (ie, what is the volume or area of a vertex?). The area of a vertex is computed as the mean of the adjacent triangles of the vertex. The volume is the mean of the neighboring truncated tetrahedra. When you run mris_preproc, it will apply a jacobian correction (like VBM). Otherwise, it operates the same as if you had a thickness value at the vertex, ie, same GLM, etc. Make sure to use permutation for correction of multiple comparisons.

On 2/21/2022 12:13 PM, Laura Willers de Souza wrote:

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Hello FreeSurfer Developers,

I would like to know if it is correct to perform volume and surface area analysis using freesurfer's GLM!?

In several mailing list questions I have already seen instructions for performing these types of analysis. But I understand that freesurfer does vertex-wise analysis in the 2D surface space. So, it is not clear to me how it is possible to evaluate a 3D measurement, as volume, with a 2D method!?

I've also read that surface area analysis via vertex-wise analysis doesn't make much sense. The best would be to do ROI-based analysis. Can you explain that to me?

Thanks in advance!

*Laura Willers de Souza *

Master Student in Biochemistry

Zimmer Lab - Federal University of Rio Grande do Sul

• Porto Alegre/RS - Brazil

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