Hi Julie
> Thank you for your detailed responses and references.
>
> Regarding Dr. Peelle's comment:
>
> 3) For many studies we need not obsess over whole-brain results and
> whole-brain corrections for multiple comparisons. Spatially
> restricting hypotheses (in a manner independent of the data being
> tested) is an excellent way to increase sensitivity to specific
> effects. This could include ROI analyses or using an explicit mask to
> focus on a subsection of the brain.
>
> Two questions:
> 1) If I were to use an explicit mask of WM (e.g., average of all subjects WM sementations) when performing tensor-based morphometry, would I still need to be concerned about correcting for multiple comparisons?
>
> 2) When should the explicit mask be used, i.e., within the second-level stats model or during specification of results output?
ok I'll try to answer for Jonathan ...
1) yes you are still concerned for multiple comparison, your mask only
reduced the search space which nevertheless still contains few thousand
voxels (and thus as many comparisons)
2) well I don;t know for TBM but in general I would go for the stat
model so that smoothness is accounted for this bit of the brain you are
analyzing ; in the other option smoothness would be whole brain and then
you mask the outputs reducing the nb of tests only (I think)
Cyril
> Thank you,
>
> -Julie
>
> Julie E. McEntee, M.A., C.C.R.P.
> Image Processing Technologist
> Center for Neuroscience& Regenerative Medicine, NIH/USUHS
> The Henry M. Jackson Foundation for the Advancement of Military Medicine
> NIH Clinical Center
> B1N264B
> 301-451-1869
> [log in to unmask]
>
> Department of Psychiatry- Neuroimaging
> Johns Hopkins University School of Medicine
> 600 N. Wolfe St./ Phipps 300
> Baltimore, MD 21287
> [log in to unmask]
>
>
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