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Hi Zarinah We have taken the approach of individualizing the subject ROI's. One way to do this is to calculate group statistics to get various maxima of activation. Then select individual subject ROI's with centers within some "acceptable" distance of the group activation. Depending on the site of the ROI and your hypotheses this could range from a few mm to perhaps a cm. We usually threshold the individual maps around 0.001 uncorrected so that the visible voxels likely have something to do with the contrast (vs. using a threshold of 1 where many voxels would have no relationship to the contrast). In some cases, however, subjects will not have any activations at the appropriate location. Those subjects may have to be dropped from the PPI analysis. darren ==============Original message text=============== On Thu, 13 Sep 2007 8:15:09 am CDT Zarinah Agnew wrote: Hi all, I am trying to carry out a PPI analysis on a data set and I have a question about how to apply the same ROIs to individual subject data. If I create 10mm ROIs from the maximal peak on the RFX analysis of 20, I cannot apply these to individual data because some subjects have no activation at these coordinates, even at a low threshold (0.05). How do I do this? Thanks in advance! Zarinah Zarinah Agnew Cognitive Neuroimaging Group MRC Clinical Sciences Centre Imperial College London Hammersmith Hospital Campus Du Cane Road London W12 0NN [log in to unmask] www.csc.mrc.ac.uk ===========End of original message text=========== -------------------------------- Darren R. Gitelman, M.D. Department of Neurology 710 N. Lake Shore Dr. #1122 Chicago, IL 60611 Voice: (312) 908-8614 Fax: (312) 908-5073 --------------------------------