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Dear Alex, >I also get some contrasts that show no activation whatsoever. This is >strange since these are my main contrasts and the task is based on one >that has already been reported in the literature. This only happens for >some individuals (I'm just doing single-subject analyses atm), and I was >wandering whether this was just due to normal variation, or the symptom of >something more sinister that I'm not aware of? Just to add to Christian's response... If this is a cognitive task (rather than primary sensori-motor), the variability between individuals is typically rather high so not finding "significant" activations in some individuals is no surprise. If you don't find the activation you're expecting the group stats, then it is worth going back and checking the individuals to determine why. >On contrasts (and in subjects) where there is activation, the output only >seems to report results for very large (>100 voxels) clusters, when I can >see that there are also smaller clusters. Is there anyway to get the z >values and coordinates of the smaller clusters? Yes, this is what cluster statistics do. An activation is considered significant if its spatial extent is significantly larger than one would expect by chance. To reduce the size of the expected clusters, increase the Z value. To see more or less everything of potential interest, put the Z-value at some reasonably lenient level (like 3.1) and set p=1.0. Now you have uncorrected p<0.001 values with no extent threshold and you can see what's there. This is exactly equivalent to simply loading the zstat image into fslview and setting the minimum value to 3.1. In general, I would recommend that this is always a useful step in getting to know you're data. Hope this helps. Joe -------------------- Joseph T. Devlin, Ph. D. FMRIB Centre, Dept. of Clinical Neurology University of Oxford John Radcliffe Hospital Headley Way, Headington Oxford OX3 9DU Phone: 01865 222 494 Email: [log in to unmask]