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Hello, I am doing an analysis that requires 3 EVs, with the third being an interaction between the first two. It asks you to "make zero" parts of the first two EVs. I kept the default values in for perfusion (which is what I am doing), and our data still looks wrong. The defaults for perfusion say to set EV 1 (the control-tag sequence) to "center" and EV 2 (the BOLD signal) to "min". We only get activation in our "negative perfusion" contrasts, and it looks like artifact (rings around the head). The wiki also mentions I should click a "Demean EV" button, which I do not see on FSL FEAT 5, which is what the wiki is written for. (http://www.fmrib.ox.ac.uk/fsl/feat5/perfusion.html). Which parts of the EVs do I set to zero and could someone explain what exactly it means to set parts of the EV to zero with more detail than the wiki (http://www.fmrib.ox.ac.uk/fsl/feat5/detail.html) ? Also, what is up with the non-existent "Demean EV" button? Thank you, Natalie Paul Duke-UNC Brain Imaging and Analysis Center Durham, NC, USA