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Dear Jon, >Not sure if this is a sensible question, I must admit that I am not sure what your question means. So I am certainly not going to be able to supply a sensible answer. >but here goes... >On the results page you may have a large blob, which contains >several bloblets each with their own coordinates. Well, several sub-peaks anyway. They all belong to the same 'blob' though. However, if you were to increase the statistical threshold they would split up into 'bloblets' I suppose. >Is it possible to find out what proportion of the total cluster size >is attributed to each of these sub-clusters? Every voxel in the cluster is significant in its own right, rather than because of its proximity to a peak. So in that sense it can't really be 'attributed to' one of the peaks. However (and it's a big however), your data has been spatially smoothed prior to statistical analysis. So some of the experimentally interesting variance in the voxel may really have been acquired from a neighbouring voxel during the smoothing process. This is mathematics beyond my rather primitive level of understanding, but I wouldn't imagine that you could recover from the smoothed data what this proportion of 'interesting' variance might be. After all, the high spatial frequency information has been lost. I imagine that you would have to go back to the unsmoothed data. If you took a particular voxel in your cluster and went back to the unsmoothed data, ran the statistics, and this voxel came out significant (at the uncorrected level say), then this would presumably indicate that the fact that this particular voxel cannot be 'attributed' to any of the sub-peaks, but is significant in its own right. So I reckon the answer is 'no', but I don't know if I have answered the question that you are really asking. Is it possible, from what I have written, for you to rephrase your question? Perhaps you could indicate the nature of the biological question that you are trying to address. Best wishes, Richard. -- from: Dr Richard Perry, Clinical Lecturer, Wellcome Department of Cognitive Neurology, Institute of Neurology, Darwin Building, University College London, Gower Street, London WC1E 6BT. Tel: 0207 679 2187; e mail: [log in to unmask]