Hi Mike,
a couple of things. One is that creating your own average will give you a
better ability to see what the true anatomical localization of your effects
are. Another is that you can re-register your subjects to your own atlas,
and possibly obtain better registration, particularly if your population is
substantially different from the ones in our atlas (e.g. young kids maybe).
cheers,
Bruce
On Thu, 27 Mar 2008, Michael Harms wrote:
Hello,
There have been numerous posts recently related to the creation of a
study specific "average subject". I have a question about the
purpose/motivation of this for surface-stream analysis/visualization
that I was hoping someone could clarify.
Specifically, my understanding is that the annotation/labels for any
derived study specific average subject are determined by the "buckner40"
gcs file (for the case of the desikan atlas). And similarly, the
average surface (e.g., white, pial) and curvature-format files (e.g.,
curv, sulc, thickness) are registered across subjects via sphere.reg,
which is determined by ?h.curvature.filled.buckner40.tif?
So, since the annotation and registration for any study specific
"average subject" is going to be determined by the "buckner40" set of
subjects regardless of the specific subjects in a particular study, what
is the purpose, advantage, or necessity for creating a study specific
average subject? Or stated differently, since the whole FS approach for
registering surfaces (and by extension parcellating the cortex) is based
on the assumption that the "buckner40" set of subjects is an appropriate
registration and parcellation target for ALL studies, what is the point
of creating a study specific average rather than using the default
'fsaverage' (which has the advantage of being created from the same set
of 40 subjects that drive the registration itself)?
Please help me understand what I'm missing here.
thanks,
Mike H.
P.S. Am I correct in presuming that the same 40 subjects were used for
the Desikan GCS atlas and for deriving the spherical registration (.tif)
target?
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