You can pass custom design and contrast matrices to mri_glmfit, so you can pass the same matrices to mri_glmfit that you would use with spm. Alternatively, you can set up an fsgd file with a 3rd continuous variable that is the produce of the first two.

doug

Jerry Yeou-Wei Chen wrote:

Hello,
I would like to know how to examine an interaction between continuous variables.
In SPM, my understanding is that a new interaction regressor, comprised of the product of the two continuous variables of interest, can be coded and entered into the model.
Would this be appropriate for CTA group analysis in FreeSurfer? Is there any difference if I use the old command line method or the QDEC GUI?
Thanks,
- Jerry
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