Hi, sorry for the late response. No, there is nothing else you have to
do. Using perm is a really good idea with volume and area, so glad to
hear that is what you are doing.
best
doug
On 3/10/2022 8:21 AM, Laura Willers de Souza wrote:
External Email - Use Caution
Of course!
To do GLM for volume and surface area analysis, is there any change in
commands in relation tocortical thickness analysis? 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.
Many thanks!
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On 3/09/2022 15:20 PM, Douglas N. Greve wrote:
Can you just ask the question again so I don't have to sort it out myself?
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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.
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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.
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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!
Att,
*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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