Dear Aggie,
you can find more detailed information in some older discussions about that issue:
https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=spm;99df675e.1006
https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=SPM;ab54c69d.1005
https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=spm;164f0e2c.1005
Best,
Christian
________________________________________
Christian Gaser, Ph.D.
Departments of Psychiatry and Neurology
Friedrich-Schiller-University of Jena
Jahnstrasse 3, D-07743 Jena, Germany
Tel: ++49-3641-934752 Fax: ++49-3641-934755
e-mail: [log in to unmask]
http://dbm.neuro.uni-jena.de
On Wed, 30 Jan 2013 19:28:13 +0000, Aggie McMahon <[log in to unmask]> wrote:
>Hi all,
>
>I have an argument that I've found evidence for on both sides: When analyzing to find GM differences between groups, and using VBM8 with the modulated m0 images, is it theoretically sound to not use TIV as a covariate?
>
>from http://dbm.neuro.uni-jena.de/?s=statistical+model we have our suggestion but I'd like to know more details behind this, if possible.
>"The idea behind this option is that scaling of affine normalisation is indeed a multiplicative (gain) effect and we rather apply this correction to our data and not to our statistical model. These modulated images are indicated by “m0″ instead of “m” using the VBM5.1 toolbox. If you decide for this option there is no further need to correct for different brain size in the statistical model."
>
>thanks!
>
>Aggie
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