Hi Gui,
The motivation comes from a discussion we had on the list a few months
(maybe more?) ago. FSL 3.1 used a more restrictive masking procedure
that ended up losing voxels that were clearly inside the brain. A few
of us complained that this was overly conservative and that the
original masking approach was better precisely because we don't lose
intra-brain voxels. The cost is the potential for false positives
with activation outside the brain, although in my experience, this was
not a serious problem, at least not at a group level. I take your
point, though, that it is labor intensive to fix such voxels if they
form significant parts of clusters, etc.
I think Steve and the FSL team are getting conflicting feedback -- too
restrictive or too lenient? Steve if you guys could just get it
perfect, the whole problem would just go away! :)
Joe
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