A lower threshold such as 2 or 2.5 would still give
valid corrected results (if you have some). It also
depends on what you're looking at: if you expect
strong effects related to a model of neurodegenerative
disease in your monkeys for instance, a too liberal
threshold might be more difficult to be accepted by
the reviewers...
Cheers,
Gwenaelle
--- Brittany Copp <[log in to unmask]> a écrit :
> I was hesitant to change the threshold since I
> didn't want to go any lower
> than is generally accepted for this kind of
> analysis. What is usually
> expected for this kind of voxelwise analysis?
>
> Brittany
>
> On Jan 9, 2008 1:02 PM, Gwenaëlle DOUAUD
> <[log in to unmask]> wrote:
>
> > Hi Brittany,
> >
> > from what I can see, what you've done is just
> fine. I
> > am not sure that you've got the same problem as
> David
> > Gutman, as you do not seem to have *blank*
> > FWE-corrected results (the fslstats -R option
> would
> > then return a: 0.0 0.0 and, in this instance, that
> > would be a problem to be solved by Matt), but
> results
> > that are lower than 0.95.
> > This is not surprising as the FWE correction is
> pretty
> > conservative. I've seen that you've also run the
> > cluster-based correction. Do you have any
> significant
> > results? If not, you might want to adjust the
> value of
> > the -c option (have a look at your tstats maps to
> have
> > a feeling of the most appropriate threshold...).
> >
> > Hope this helps,
> > Gwenaelle
> >
> >
> > --- Brittany Copp <[log in to unmask]> a écrit :
> >
> > > Hey all,
> > >
> > > I ran TBSS with our macaque data and everything
> > > seemed to work well, except
> > > that the FWE-corrected images do not show
> anything.
> > > It is possible that no
> > > differences survived after the correction, but I
> > > wanted to make sure it
> > > wasn't a scripting error. There were 10 control
> > > subjects and 9 experimental
> > > subjects, and I am just interested in whether or
> not
> > > there are differences
> > > between the two groups. I am attaching all of
> the
> > > command lines that I
> > > used. Thanks in advance for your help!
> > >
> > > Brittany
> > > > ##The following were run in a directory
> containing
> > > all of the subjects' images (named
> > > CON_01_dti_data_FA.nii.gz….
> > > CON_10_dti_data_FA.nii.gz and
> > > MAL_01_dti_data_FA.nii.gz….
> > > MAL_09_dti_data_FA.nii.gz)
> > >
> > > tbss_1_preproc \
> > > tbss_2_reg –n \
> > > sh tbss_3_postreg_noMNI.sh -S target.nii.gz
> > > tbss_4_prestats 2000
> > > design_ttest2 design 10 9
> > > randomise -I all_FA_skeletonised.nii.gz -o tbss
> -m
> > > mean_FA_skeleton_mask -d design.mat -t
> design.con -n
> > > 5000 -c 3 -V
> > >
> > >
> > >
> >
> >
> >
> >
> >
>
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