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Dear Marta, > I'm looking for a way to extract the average signal of a cluster (of > activation map) > in order to analyse it. Is it possible within SPM99 do this? > I would like to add some additional questions to the above request, > though perhaps it's already implied in the previous message. > Is it possible within SPM99 to plot the average behavior of all > significant voxels in a small cluster rather than plotting for just a > single selected voxel? And it is possible analyse separatly the signal > of > two or more adjacent clusters? Yes, yes and yes. To make SPM99 extract a signal from a cluster, you need some update to spm_regions.m, which I just copied into the update-section. ftp://ftp.fil.ion.ucl.ac.uk/spm/spm99_updates/ You'll need three files: spm_regions.m spm_filter.m spm_dcm_display.m In the results section, click onto the 'V.O.I.' button and follow the instructions. SPM will then extract the first eigenvariate from a cluster, which is similar to its average signal, but provides a better representation of what is going on in the cluster over time. The extracted first eigenvariate can be accessed as variable Y in the matlab workspace. Stefan -- Stefan Kiebel Functional Imaging Laboratory Wellcome Dept. of Cognitive Neurology 12 Queen Square WC1N 3BG London, UK Tel.: +44-(0)20-7833-7478 FAX : -7813-1420 email: [log in to unmask] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%