On Mon, 20 Apr 2009 20:25:19 +0000, Yune Lee <[log in to unmask]>
wrote:
>Dear SPM users,
>
>I'm trying to figure out the loci of the actived voxels is on the sulci or
>gyri.
>The voxels come out from the group level analysis and the image was only
>normalized (not smoothed) to the MNI EPI.
>How do people usually find out the exact loci of the MNI coordinates?
>Any help/ advice would be greatly appreciated.
>
>Thanks,
>YSL
There are many ways to do this. Generally:
* Things like the Talairach daemon (though for that itself you have to be
careful whether the "atlas" you're using is in Talairach or MNI coords)
* Overlaying activation on a T1 image
* Simply taking the coordinates and looking them up in a published atlas in
book form.
However, no method is "exact," insofar as there's a great deal of error in
localization in fMRI:
(1) Measurement of BOLD itself can be spatially imprecise ("draining veins,"
etc)
(2) There is error between a particular subject's activation and his own native
T1 because of EPI distortion
(3) Group studies usually involve warping to canonical space, and the warping
for any given subject is going to be imperfect
I'm no expert on neuroanatomy, so the following advice should be taken with a
grain of salt:
Given the inexactitude, it's not clear you can decisively conclude that an
activation is in a gyrus and not a sulcus (or vice versa). The smaller the
structure, the more difficult it is to confidently make such a classification.
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