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Hi. On Fri, 22 Mar 2002, Antti Korvenoja wrote: > I have a question concerning conjunction analyses. Or at least I believe it > should be applied in my problem. If I have experimental conditions A1, A2 and > B1,B2 and I want to determine what areas are significantly activated both in > contrasts A2-A1, B2-B1, how do I set up this in FSL? I think you are asking - where is A2>A1 AND B2>B1 - yes? Then you want to take the cluster mask images from the A2-A1 (let's call this contrast 1) contrast and the B2-B1 contrast (contrast 2) and BINARY_AND (ie multiply) them together: avwmaths cluster_mask_zstat1 -mul cluster_mask_zstat2 -bin combined_mask this gives the desired binary mask image. > Or if my desire is to find > areas that are differentially activated in these two contrasts? Do you mean (A2-A1)-(B2-B1)? that contrasts will give you where the first contrast gives greater difference than the former. However - note that you might well want to only look for differential activation like this where both contrasts are also positive - in that case then mask this result with the cluster masks (binarised to 0/1) from the individual contrasts. Hope this makes sense! ttfn, Steve. Stephen M. Smith Head of Image Analysis, FMRIB Oxford University Centre for Functional MRI of the Brain John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK +44 (0) 1865 222726 (fax 222717) [log in to unmask] http://www.fmrib.ox.ac.uk/~steve