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Hi, On Tue, 15 Mar 2011 13:29:34 +0000, R. Duke <[log in to unmask]> wrote: >Hello SPM Experts, > >I am reading the VBM8 toolbox manual and just wanted to confirm that I understand this. > >Under Modulated Normalized, Non-Linear Only is equivalent to: > >1. Affine + Non-linear with "No" overall grand mean scaling and "Proportional" Normalization. >2. Affine + Non-linear with ICV as a nuisance covariate. Neither 1 nor 2. It is equivalent to Affine + Non-linear with proportional scaling with the (inverse of the) affine scaling. The affine scaling parameter is a good approximator for ICV, see http://surfer.nmr.mgh.harvard.edu/fswiki/eTIV. > >Q1: If so, does that mean that I do not use "Proportional" Normalization when using non-linear only? >Q2: If so, does that mean I do use "Overall Grand Mean Scaling" when using non-linear only? Please do not use additional "Overall Grand Mean Scaling" or "Prpportional Scaling". If you decide for the "non-linear modulation" option this is equivalent to correct for ICV (or at least an approximator of that) and no additional correction is necessary. Regards, 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 > >I am currently using Non-linear only without ICV as a covariate, without "Overall Grand Mean Scaling," and without "proportional" normalization. Is this recommended? > >Cheers!