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Hello Doug,

Any advantages of surface-based smoothing of the gm thickness maps beside increasing signal to noise ratio? I read the paper and based on the results and conclusion, mcz with higher threshold and fwhm should be fine (though permutation is recommended) for thickness.

best,

paul

On Wed, Sep 30, 2020 at 10:37 AM miracle ozzoude <miracooloz@gmail.com> wrote:

Thank you very much Doug. I appreciate it. I guess we will have to redo our analyses based using permutation and hope the results are the same
On Wed, Sep 30, 2020 at 10:22 AM Douglas N. Greve <dgreve@mgh.harvard.edu> wrote:
For statistical analysis, the reviewer is right, see https://pubmed.ncbi.nlm.nih.gov/29288131
We are recommending permutation analysis, see

https://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/MultipleComparisonsV6.0Perm
or
https://surfer.nmr.mgh.harvard.edu/fswiki/FsPalm

On 9/30/2020 9:23 AM, miracle ozzoude wrote:
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Hello Experts,

I have a question regarding grey matter thickness map and signal to noise ratio. Does smoothing of the map increase signal to noise during surface based cortical thickness analyses? if yes or no, why? This question was asked by a reviewer in one of our manuscript because he/she thinks that one of the reasons to perform smoothing is to comply with random field theory hypotheses, when controlling for multiple testing.

We did apply multiple comparison corrections using monte carlo simulation with cluster threshold of 2, 5000 iterations, and bonferroni.

Thanks alot.

best,

Paul
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