Yes, you can just set up the contrast as you describe, ie,

mkcontrast-sess -a 1 -a 2 -c 3

will average conditions 1 and 2 and compare the average against 3.

You can recode your par file if you want, but it probably won't make any difference unless you are using an FIR model.

doug

Cameron Ellis wrote:

Hi, I have three conditions specified in my paradigm files that I have been comparing to one another. Two conditions I would like to combine and compare to the third in one contrast and was wondering if this would require modifying my paradigm files to refer to these two conditions with the same number or if I can just positively weight the two I want to combine in mkcontrast-sess and negatively weight the other. That's all. Thanks, Cameron _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer