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Dear SPM experts, I’ve checked the spm archives but I couldn’t find an answer to the following question: I’m using an event-related design, in which some events depend on the behavior of the subjects such that there are sometimes only 2 per run. Since I can not acquire the data in one long run, I would like to concatenate 5 runs (lets say each contains 200 images) to one long containing then images 1 to 1000. Right now I’m adding a constant for each run to correct for session specific effects as well as one extra covariate modeling the transition from one run to the next (not sure whether this is really necessary). I would like to highpass-filter the data and use the default SPM2 value of 128 s. If I apply this filter to the concatenated run, the “session specific-constants” are filtered too. This is clearly visible in the design matrix. My first question is: is this a problem?????? In the meanwhile, I’ve changed the spm code a little bit, such that the filtering is applied for each original run, i.e the filter is applied to image 1-200 of the concatenated data, then to image 201-400, then to 401-600 and so on. If I check the design matrix the constants look fine. Now question number 2: is this correct or do I overlook something important here? Thanks a lot, Nici _________________________________________________________________ Free blogging with MSN Spaces http://spaces.msn.com/?mkt=nl-be