On 12/21/2020 8:45 PM, Kayle Sawyer wrote:
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We are working on a manuscript revision for an fMRI project that was analyzed
with FS-FAST 5.3 years ago. We used mri_glmfit, and then we ran mri_surfcluster
(instead of mri_glmfit-sim) with a vertex-wise threshold of p<0.001 and a
cluster threshold of 100mm^2. We had applied 8 mm smoothing at the group-level,
and the voxel size was 3.125x3.125x5 (resampled to fsaverage surface and to
MNI305).
1. One reviewer asked us to provide a rough estimate of the family-wise error
rate (FWER) that a cluster threshold of 100mm^2 is equivalent to, or
alternatively, to re-analyze everything with mri_glmfit-sim permutation. It
would be simpler to provide the FWER estimate. To get the FWER estimate, we
referred to Woo et al (2014). However, their simulations were for volume
analyses, not surface analyses. What is the FWER (roughly) for a primary
threshold of p<0.001 and cluster threshold of 100mm^2? (Obviously, we are
hoping for a number less than 0.05.)
Why not run mri_glmfit-sim and just see what the p-value is for that cluster?
2. For the volume, we used mri_surfcluster with a primary (voxel-wise)
threshold of 0.001 and a size threshold of 300mm^3. If I’m understanding
correctly, Figure 2 from Woo et al. (2014) suggests a FWER p<0.05 might roughly
correspond to a cluster size threshold of 200 to 985 voxels (1600 to 7880
mm^3), depending on intrinsic smoothness. That would likely put our threshold
of 300mm^3 well above p<0.05. Is this correct?
Again, you can just run mri_glmfit-sim. I would use the version 7 for this one
though as I think the volume-based GRF might have changed since 5.3. You can do
the same for the surface-based above, but I think the 5.3 version should be ok
Thanks,
-Kayle
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