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Dear SPMers, My doubt is regarding the rfx plot toolbox. I am using it to calculate percent signal change (PSC) in my ROIs. My paradigm has four conditions (two active, one low level baseline and one high level baseline) A1, A2, B1, B2. I have defined A1, A2, and B1 explicitly in the GLM (meaning I have three regressors defined). Now, for rfxplot one needs to open an unbiased rfx contrast, which in most of the cases is an average contrast. Now, because I want to compare PSC for A1 and A2, I have the following two options- 1) [1 1 -2] OR 2) [1 1 0] So, which of the above mentioned contrasts should be used? And what are the pros and cons with respect to each? Any help would be highly appreciated! Best, D S Xanthate