dear FSL users,
i am having trouble with the masks used for featquery.
i have two groups of subjects, a young group, and an old group. in order
to do an ROI analysis, i defined a mask in the standard space. when i
run featquery, the masks in the featquery folders of the young subjects
are close to the size of the original mask and at the correct location.
the masks in the featquery folders of old subjects, however, are either
zero everywhere, or only a 3-4 voxels and slightly off the target area.
i have checked the registrations from each subject to the standard space
(12 DOF) and they look correct. when i reduce the mask threshold in
featquery (with the -i option) to .3 for older subjects, the size of the
masks increase by a few voxels.
why are the masks for older subjects often zero every where. is this a
registration problem? is reducing the mask threshold the correct
solution here?
thank you very much for any advice,
paymon
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