Hi,
On 25 Jun 2007, at 22:30, Jiansong Xu wrote:
> Dear Friends:
>
> I want to measure the volume of all regions showing activation at a
> contrast. Can I use the volumes of all the voxels surviving the
> voxel level
> threshold, e.g. p < 0.01, without correction?
It's up to you. If you think you will be required to report only
voxels that survive multiple comparison correction then you'll need
to do it.
You can easily get the volume of surviving voxels by running avwstats+
+ on the relevant thresh_zstat image.
> Because I'm searching the whole brain, any voxel has the same
> chance of
> false positive or false negative, so I do not use cluster extent
> correction,
> is it correct?
I'm not sure I follow. You would choose to use cluster-based
thresholding _if_ you want to increase sensitivity by taking spatial
extent into account.
Cheers, Steve.
>
> Thanks
>
> Jiansong
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Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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