In order to figure out what may have gone wrong, I would begin by checking how well
the spatial normalization has worked by typing something like:
spm_coregister /somewhere/spm/templates/T1.img /another/directory/normalized_image.img
at the matlab prompt. This won't actually do anything except produce a display
of how well registered the template image and normalized image are.
How are you determining that the results are moving? If you are looking at Talairach
co-ordinates, then these can be a few millimeters out. If you are superimposing the
results on to co-registered structural images then you must check that the co-registration
has worked OK. This can be a problematic step if you are doing fMRI without any
form of distortion correction (since a rigid body registration can not account for
the gross non-linear distortions found in most fMRI datasets). Try superimposing the
blobs on the mean of your normalized functional images. This should give you the best
idea of where things are really happening.
Regards,
-John
> Hello, we're running a study with 36 scans per subject in a transverse plane
> through the premotor cortex area of the brain. When we attempt an analysis of
> these images, our results are moved to another area of the brain. It also
> appears that the area that the results are moved to is the same area of the
> brain we have analyzed in a previous study (using the same participants but
> different images, obviously). Something is clearly not working correctly
> - could it be we have to re-set some variables, or reset the origin or
> something? We're stumped.
>
> Thanks very much in advance for your help!
>
>
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