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I have a statistical question about how to approach reporting results from
FreeSurfer analyses containing three groups. I ran a group effect (F-test)
and then post-hoc tests looking at pair-wise comparisons between the three
groups. My question is why is that we run separate vertex-wise analyses for
the post-hocs rather than extracting the values from significant clusters
and running post-hocs in a statistical software for just the regions where
a significance difference was found (ie the clusters)? As a post-hoc vertex
wide analysis can lead to different results.

For example in my group effect contrasts I found a cluster in the parietal
lobe. Whereas in my post hoc-vertex wide analyses one of them found two
clusters 1) within the parietal 2) within the frontal lobe. If I choose to
run these post-hoc analyses via freesurfer (ie vertex-wise) rather than
extracting the results to analyze in a statistical program, is it standard
to report the second cluster? Even though it didn't come up in the group
model? If so is there a paper that people reference that uses this approach?

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