Dear Group:
I have basic questions about the option of global normalization.
1. what is the indication for use of none, scaling for global normalization
in SPM99?
2. Why does the "ancova" in SPM96 be removed?
3. I compared the result of using scaling, ancova and none for a
somatosensory stimulation, with a realigned-only dataset for references;
please see the attached files
Fig.1 : the result of realigned, non-smoothed, non-normalized data with a
very simple correlation map
Fig.2: same of fig.1, representive slice showing right parietal activation
and its time-course.
Fig.3: render map with ancova normalization, the parietal activation is
there.
Fig.4: render map with scaling global normalization, the parietal activation
removed a lot, more deactivation spots now.
Fig.5 render map without global normalization. large activations noted.
>From figure 1, 2, my feeling is that there really have strong activation,
corresponding to somatosensory stimulation of left leg. it seems to be close
to that shown on the map with Ancova. The map with scaling seems to be too
restrictive, and have more deactivation (blue color) than other maps; Is
the deactivation true or not?
Thank you in advance
Sincerely
Ming-Ting
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Ming-Ting Wu, MD Tel: (O)886-7-3422121 ext 6205,
6235, 6212, 6201
Dept. of Radiology Tel: (H) 886-7-3461096 Fax:(O)
886-7-3468301
Kaohsiung Veterans General Hospital
386 Ta-chung 1st Rd. Kaohsiung 813, Taiwan
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