Dear Charlotte,
On Tue, 17 Apr 2012 15:50:50 +0100, SUBSCRIBE SPM Anonymous <[log in to unmask]> wrote:
>Dear SPM users,
>
>I have a question about modulation and longitudinal process. I have read previous posts and I have understand that modulation was not necessary for longitudinal treatment . When I load the batch cg_vbm8_longitudinal.m, I see that for "modulated normalized", the option is "none"! (when I run the process, I obtain wrp images).
>But when I read explanations at the bottom, I read that it is better to use for "modulated normalized" the option "non linear only" (when I run the process, I obtain m0wrp images)! I don't know what is the better way to do?! Can somebody help me?
The explanation is rather thought for the cross-sectional VBM, where modulation is always necessary.
>
>My second problem is: do I have to put the TIV as covariate in my statistical model? for wrp images? for m0wrp images?
For cross-sectional data that were modulated with the non-linear terms only (m0wrp images) no additional TIV is necessary. Because we don't use modulation for longitudinal data we rather analyse absolute volume changes over time. If you intend to focus on relative volume changes over time the inclusion of TIV might help.
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
>
>Thank for all.
>All the best,
>Charlotte
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