The only time I have seen a study use multiple thresholds on the same
data was in the following paper:
Burton et al. Cortical Network for Vibrotactile Attention: A fMRI
Study. Human Brain Mapping. 29:207–221 (2008).
"Four corrected F-statistic Z-score maps were computed
using different significance thresholds to capture both low
and high amplitude signals in, respectively dispersed and
focal clusters. The criteria for Z-scores with P ¼ 0.05 were
z ¼ 3.0, 3.5, 4 and 4.5 over, respectively, at least 45, 24, 12,
and 5 face-connected voxels. The different threshold zscore
maps were combined by retaining only the significant
Z-score from corresponding voxels, which thereby
indicated the distribution of significant activity irrespective
of cluster size. The combined task specific, thresholded Zscore
maps were binary coded and used to create conjunction
maps. Thus, for each participant there were F-statistic
Z-score maps for each of the tasks and corresponding binary
coded maps."
However, in that paper, the cluster threshold, from which the
inferences were drawn was always set to p<0.05. When you use FWE in
some regions and not others, neither the voxel nor cluster thresholds
are the same. To me this is a problem.
Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Postdoctoral Research Fellow, GRECC, Bedford VA
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
Office: (773) 406-2464
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On Sun, Jun 26, 2011 at 9:10 AM, Jonathan Peelle <[log in to unmask]> wrote:
> Hello,
>
>> Is any possibility to save T-map with FWE-correction in some region and
>> without FWE outside this region?
>
> There's not a straightforward way of doing this—I think you'd want to
> save 2 statistical maps thresholded differently (using the "save"
> button after getting results), and then combine them using imcalc
> (using some expression like i1+i2, after selecting these two
> thresholded maps).
>
> That being said, I think it can be dangerous to combine statistical
> thresholds without visually distinguishing between the two, since they
> may have very different interpretations. It probably depends on the
> particular question one is trying to address, but in general I would
> think rendering two separate statistical maps in different colors,
> clearly distinguishing the statistical thresholds, would be the best
> way to go.
>
> Hope this helps!
>
> Jonathan
>
> --
> Dr. Jonathan Peelle
> Department of Neurology
> University of Pennsylvania
> 3 West Gates
> 3400 Spruce Street
> Philadelphia, PA 19104
> USA
> http://jonathanpeelle.net/
>
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