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Dear Cyril and Helmut, I proceeded to do the following contrasts at both the first and second timepoints. 1) LR - L – R aka [ 1 -1 -1 0] 2) (LR + REST) – (L + R) aka [1 -1 -1 1] 3) (LR – L) ∩ (LR – R) aka select both [1 -1 0 0] [1 0 -1 0] There is little to nil activation in all contrasts for both timepoints... except for a very bizarre result for contrast 1 at the second timepoint. I have attached 3 screenshots: for contrast 1 at both timepoints and LR-REST. How is it possible that contrast 1 at timepoint 2 yielded so much more activation than LR-REST? I have re run the entire analysis 3x. Other contrasts appear to make sense except for this. Additionally, all these contrasts seem to show over-additive effects. How do you show under-additive effects? In my experiment, I'm trying to map out how different if any (whether more or less) LR is to sum of L and R. Thanks! Pei Ling