Indeed - it sounds like the reviewer doesn't understand cluster-based
thresholding. The Z>2.3 is the cluster-forming threshold - the
resulting clusters are then tested for significance using random field
theory (see refs from Michael) with a final significance test of
P<0.05 corrected for multiple comparisons.
Cheers.
On 10 Apr 2009, at 20:54, Michael T Rubens wrote:
> Hi Jen,
>
> • Benjamini, Y. & Hochberg, Y. (1995). Controlling the false
> discovery rate: a practical and powerful approach to multiple
> testing. Journal of the Royal Statistical Society, Series B,
> 57:289-300.
> • Friston, K.J. (1997). Testing for anatomically specified regional
> effects. Human Brain Mapping, 5:133-136.
> • Genovese, C.R., Lazar, N.A. & Nichols, T.E. (2002). Thresholding
> of statistical maps in functional neuroimaging using the false
> discovery rate. NeuroImage, 15:722-786.
> • Worsley, K.J., Marrett, S., Neelin, P., Vandal, A.C., Friston,
> K.J., and Evans, A.C. (1996). A Unified Statistical Approach for
> Determining Significant Signals in Images of Cerebral Activation.
> Human Brain Mapping, 4:58-73.
>
> -Michael
>
> On Fri, Apr 10, 2009 at 12:41 PM, Jennifer Townsend <[log in to unmask]
> > wrote:
> Hi,
>
> I'm looking for a citation or two justifying the use of
> cluster-based thresholding for within and between-group results from
> FEAT. A reviewer has questioned the use of Z scores < 3 as being
> extremely leniently and sub-threshold. We used the default setting
> of Z>2.3 with corrected p=.05, but I can't find the citations
> explaining the use of cluster vs. voxel-based thresholding aside
> from the explanation on the website. Can you please point me in the
> direction of some papers explaining or defining this method?
>
>
>
> Many thanks
>
> Jen
>
>
>
> --
> Research Associate
> Gazzaley Lab
> Department of Neurology
> University of California, San Francisco
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FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
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