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Hello, I have a few (ok, I admit, a lot of) questions concerning contrasts in SPM. We have done a study on 25 subjects, with a block design of 2 conditions + baseline. When I do a analysis with a [1 0 1 0 ...] t-contrast vector to test cumulative effects of condition A, is this the same as [1/25 0 1/25 0 ...], or should I always normalise (sum to 1) these kind of contrasts ? Is this correct for a multiple subject analysis, or only appropriate for combined effects within the same subject ? Does this contrast mean I'm testing a H1:"at least one subject activates for condition A significantly" ? When I'm using a differential contrast, e.g. [1 -1 1 -1 ...] for effect A > effect B, I get a lot of activation. Should I mask with the A>0 contrast to filter out B < A < 0 (both effects below baseline) ? If yes, how are the superfluous B < A < 0 area's to be interpreted. They are below baseline, but according to the analysis they do differ significantly for effects A and B, so there is something happening that differs for A and B. Thanks to anyone willing to help me out here, Peter Clerinx, Physicist, MR department AZ-VUB, Brussels.