Thank you for your reply. Having earlier read some past posts on this and part of the
useful document at
I am now ready to comfortably conclude from your 1st and 3rd sentences that I have the
confirmation I was asking for. I appreciate your other comments that are a concise
summary of important details about the other two options.
On Tue, 14 Jul 2009 02:34:14 -0500, MCLAREN, Donald <[log in to unmask]>
>The con_*.img, ess_*.img, spmT_*.img, and spmF_*.img are not effected in
>anyway by None/FWE/FDR selection or changing the spatial extent.
>Selecting None/FWE/FDR only changes what is shown in the results display.
>None makes no voxel-wise correction. FDR does not take into account the
>spatial resolution, it simply uses a formula based on the number of voxels
>in the image. FWE takes into account the spatial resolution/smoothness in
>computing the voxel-wise correction. Both correction methods are correcting
>for the significance at the voxel level.
>The spatial extent threshold is completely separate of the the correction
>above. Anytime you set the extent threshold above 0, it looks for clusters
>that have at least that many (edge-connected, I believe) contiguous voxels.
>The results display will be unchanged if all the clusters in the image were
>larger than the spatial extent threshold set compared to when it was set to
>Hope that answers your question.
>On Mon, Jul 13, 2009 at 4:38 PM, Yaman Aksu <[log in to unmask]> wrote:
>> For None (among None/FWE/FDR), I would like confirmation that the inference
>> that is
>> computing spmT_*.img is indeed on an entirely voxel-by-voxel basis (i.e.
>> makes no use of
>> spatial relations of voxels). This is to mainly confirm that Random Field
>> Theory, which I am
>> aware is used by FWE, is definitely not being used by None.
>> P.S.: When using None, as a useful thing I checked spmT_*.img was not
>> affected by the
>> choice of Extent Threshold value (e.g. 0 or 10), but I believe this check
>> is not sufficient for
>> the confirmation I'm asking for.
>> Thank you.
>Best Regards, Donald McLaren
>University of Wisconsin - Madison
>Neuroscience Training Program
>Office: (608) 265-9672
>Lab: (608) 256-1901 ext 12914
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