Yes, the regressor order is in the order of the classes and varialbles as listed in the FSGD. For DODS (the default), there will be a regressor for each variable for each class. If you have any doubts, you can look at the Xg.dat file created by mri_glmfit. This is the design matrix which should make very clear which regressor corresponds to which class/variable.

doug

On Fri, 7 Sep 2007, Juergen Haenggi wrote:

Dear Freesurfer users

In order to be absolutely sure about the direction of a contrast I have the following question:

gamma = 1*beta1 + -1*beta2 + 0*beta3 + ....

Does beta1 always correspond to the class that is entered most superior in the fsgd file and beta2 to the class that is entered as the second class in the fsgd file?

Do the other betas correspond to the variables listed from left to right in the fsgd file?

Thanks for your confirmation. Best regards Juergen Haenggi

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Juergen Haenggi Ph.D. (Dr. des.) Division of Neuropsychology Institute of Psychology University of Zurich Binzmuehlestrasse 14, PO Box 25 8050 Zurich, Switzerland 0041 44 635 73 97 (phone office) 0041 76 445 86 84 (phone mobile) 0041 44 635 74 09 (fax office) BIN 4.D.04 (office room number) j.haenggi@psychologie.uzh.ch (email) http://www.psychologie.uzh.ch/neuropsy/ (website) http://www.juergenhaenggi.ch (private website)

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