Can you just ask the question again so I don't have to sort it out myself?
On 3/2/2022 3:30 PM, Laura Willers de Souza wrote:
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Sorry about that!
I'm resending with previous emails.
The first message below is the one you didn't know how to respond to because you didn't have the previous e-mails.
On 2/22/2022 9:15 AM, Laura Willers de Souza wrote:
Thanks so much for the explanation!
There is something different in the analysis of volume and surface area in relation to the analysis of cortical thickness? Like some more command, or some other detail that must be changed (besides, of course, the flag that specifies the measure to be analyzed) - I'm already using permutation in the correction of multiple comparisons.
On 2/21/2022 15:20 PM, Douglas N. Greve wrote:
Yes, it is. It is confusing when you talk about area and volume sincethese are not point measures like thickness (ie, what is the volume orarea of a vertex?). The area of a vertex is computed as the mean of theadjacent triangles of the vertex. The volume is the mean of theneighboring truncated tetrahedra. When you run mris_preproc, it willapply a jacobian correction (like VBM). Otherwise, it operates the sameas if you had a thickness value at the vertex, ie, same GLM, etc. Makesure to use permutation for correction of multiple comparisons.
On 2/21/2022 12:13 PM, Laura Willers de Souza wrote:
Hello FreeSurfer Developers, I would like to know if it is correct to perform volume and surfacearea analysis using freesurfer's GLM!? In several mailing list questions I have already seen instructions forperforming these types of analysis. But I understand that freesurferdoes vertex-wise analysis in the 2D surface space. So, it is not clearto me how it is possible to evaluate a 3D measurement, as volume, witha 2D method!? I've also read that surface area analysis via vertex-wise analysisdoesn't make much sense. The best would be to do ROI-based analysis.Can you explain that to me? Thanks in advance!Best,
Laura.
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