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Dear DCMers, we have an n-back paradigm with two levels of working memory load (i.e. two of the three conditions in our blocked design). We'd like to enter a parametric modulator of these two conditions as an experimental modulation in the B Matrix. The respective DCM modulatory input is attached. It is probably just mean scaled (we entered 1 and 2 as pmod.param), but we are unsure how to interpret e.g. positive effects of this input function in the estimated DCM. Does a positive parameter estimate signify an increasing positive coupling with increasing working memory load (as intended)? It could also mean a decreasing coupling with low working memory load and a positive coupling with high load. If the first interpretation is correct, how will intervals with the input being zero (see picture) be interpreted? We would like DCM to test for changes in coupling only for the non-zero sections and specifically do not want them to be considered as an intermediate working memory load (between the positive and the negative values). It would be great if someone could help us to understand why the conditions are depicted like that and how resulting positive/negative parameter estimates should be interpreted. Many thanks, Elisa