the average subject is constructed by specifically trying to normalize
out differences in folding so I wouldn't try to infer anything from it
cheers
Bruce
On
Tue, 2 Apr 2013, Klein, Holger wrote:
Hi Bruce,
Thanks for the quick reply. I took the individual surface values from every
subject's aseg-file and calculated the mean.
Visualization was made in tksurfer with the average subject.
Thus, I am still wondering about this discrepancy.
Any other hints?
Thanks, H
2013/4/2 Bruce Fischl <fis...@nmr.mgh.harvard.edu>
Hi Holger
how did you calculate the surface area? And how are you visualizing it? I
wouldn't use the surface area of
the average subject for anything other than visualization as the
coordinate system is not linear. You need to
compute the surface area in the individual subject coordinates or take
the jacobians into account.
cheers
Bruce
On Tue, 2 Apr 2013, Klein, Holger wrote:
Dear Freesurfers,
I averaged 42 subjects with make_average_subject focusing on Heschl's
Gyrus and finally got the image
attached (for both
atlases (Desikan = Atlas I, Destrieux = Atlas II).
Gray matter surface calculations for Heschl's gyrus showed the following
mean values (in mm^2):
Atlas I lh = 439 (SD 60), rh = 323 (SD 46)
Atlas II lh = 340 (SD 70), rh = 253 (SD 47)
Heschl's gyrus depicted in the attached image looks considerably larger
for Atlas II, but the surface
analysis gives me
smaller values for mean surface calculation (Atlas II < Atlas I)
How can that be explained?
Thanks in advance
[cleardot.gif]
Holger
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