Dear SPM community,
can anyone explain the following surprising smoothness estimates:
In an effort to assess the overlap between a group level contrast (3x3x3
mm^3 EPI voxel resolution) and an anatomical map (1x1x1 mm^3 voxel
resolution) I resliced the single subject contrast images via the SPM2
GUI ("coregister" & "reslice only" to the colin27 T1 image). Next I
included the resliced con images in a second level analysis and plotted
the default SPM glass brain. The t-maps look similar to those obtained
from the analysis of the original contrast images with 3x3x3 mm^3 EPI
voxel resolution - of course they are now much less grainy. However the
glass brain plot footer indicates that the estimated smoothness FWHM is
0.1x0.1x0.1 {mm} (see first attached screenshot). - How can this be
explained?
One other observation that might be connected to the aforementioned is
that the resliced contrast images are surrounded by a box of "NaN",
whereas directly at but outside of the brain the voxel values are "0"
(see second attachment screenshot).
Any suggestions? - Thanks,
Marcus.
--
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Dr. Marcus Wilms
Cognitive Neurology Group
Institute of Medicine
Forschungszentrum Juelich
52425 Juelich, Germany
Phone: +49 (02461) 61-6184
E-Mail: [log in to unmask]
Home: http://www.netwilms.net
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