Re: [Freesurfer] grey matter thickness map and SNR

Only that the parametric assumptions are better met and so mcz controls the FPR better

On 9/30/2020 2:29 PM, miracle ozzoude wrote:

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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 mailto: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 <mailto: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:

...

            External Email - Use Caution

    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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