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Hi. We have an fmri dataset in which data were collected for three conditions (B=baseline,X=condition X, Y=condition Y) in the same scan, during both memory encoding and memory retrieval. let's call the encoding conditions eB, eX, and eY, and the recognition conditions rB, rX, and rY. What we'd like to do is a conjuction analysis in which we look for regions that were active for a certain condition (X or Y) across encoding and recognition, and another where we look for regions that are active for either encoding or recognition across both conditions (X and Y). this is in the context of a random effects analysis, for which I've created adjusted mean images of each of the 6 conditions for each subject. Thus the conjunctions that we'd like to do are: common encoding: (eX - eB) && (eY - eB) common recognition: (rX - rB) && (rY - rB) common X: (eX - eB) && (rX - rB) common Y: (eY - eB) && (rY - rB) The question that I have (ignoring for the moment the other recently discussed issues about conjuctions and random effects) is: How inappropriate is the first set of conjuctions, since the baseline is common across the two contrasts and the contrasts are thus not independent? thanks, russ ---------------------------------------------------------------------- Russ Poldrack Phone: (650) 725-0797 (NOTE NEW AREA CODE!) Dept. of Psychology Fax: (650) 725-5699 Stanford University Jordan Hall Email: [log in to unmask] Stanford, CA 94305 Web Page: http://www-psych.stanford.edu/~poldrack/ ---------------------------------------------------------------------- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%