What were the spatial characteristics of the "activation" which you
added? Were they "strong" enough that you would expect to see them using
cluster thresholding with a Z of 2.3 and a p<0.01? Obviously this depends
on both the magnitude of the activation as well as the spatial extent, and
of course depends critically on the number of resels in the data set.
I know SPM2 defaults to using voxel statistics but then provides
corresponding cluster info in the columns on the left. I didn't recognize
the other package you mentioned so I don't know what it uses. So one
possibility could simply be that you're seeing a fairly typical
thresholding effect due to the specific values chosen as defaults across
the various packages.
Joe
--------------------
Joseph T. Devlin, Ph. D.
FMRIB Centre, Dept. of Clinical Neurology
University of Oxford
John Radcliffe Hospital
Headley Way, Headington
Oxford OX3 9DU
Phone: 01865 222 738
Email: [log in to unmask]
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