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Dear Krishna, Thanks for your reply. My experiment has 2 contrasts A and B in one spm.mat, two other contrasts C and D in second spm.mat and similarly E and F in third spm.mat. All I need to do is a conjunction of A to F. Given this scenario, can you please elaborate a little more on the first approach of Random effects analysis. Atesh > Dear Atesh, > > The conjunction principle as in Nichols et al. paper is that the minimum t > value of all the contrasts will become the t value of the conjunction. > Hence the correct method of doing conjunction is to do a random effects > analysis and use the contrasts [1 0 0], [0 1 0] and [0 0 1] and do a > conjunction between them. The alternative option is to do three one-sample > t-tests, threshold them and do an imcalc to get a map where all the three > overlap. if you want to know how much is the overlap, example in contrast > A, the t-value may be 5 where as in contrast B, the t value may be 3. This > you can do by using MRIcron or slover by projecting blobs of different > colors e.g. red, blue, green and selecting the transparency of the colors, > you can get the overlap areas using the usual RGB combinations. In general > the Random effects analysis will be useful if you want to further probe > into the results of your experiment such as finding the difference between > contrasts A and B etc. > > The other methods like implicit masking should not be used for > conjunctions, because the t-value you get are from the main contrast > selected. Masking only filters out voxels not active in the second > contrast. > > HTH > >