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Dear Chris and Julie, You should adjust your data for anything that is a known confound, e.g. realignment parameters. If you deliberately zoom in on a particular set of experimental manipulations and disregard other manipulations, then the latter could be regarded as confounds and removed through adjusting your data during VOI extraction. I would be a little careful with this though since it questions the rationale of the experimental design that you chose in the first place. There may be very good reasons to do this but it always depends on the specific application. I'd say there is no general rule here (except that all sessions should be treated identically in this regard). BTW, congratulations on your recent DCM paper in Science, Chris! All the best Klaas At 08:21 06/12/2006, you wrote: >Hi Klaas and other experts, >when defining a VOI, SPM asks whether we want to "adjust data for... >effects of interest" and several mails on this list indicate that it >is important to >do this when defining a VOI for DCM. >e.g. >http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind05&L=SPM&P=R580878&I=-3 > >Our question is: in the situation >where you have several regressors in your design matrix, but not all of >them are included in your DCM model, should you correct for effects of >interest across ALL regressors, or only those which you want to include? > >Similarly, given that the VOI is defined on a session-by-session basis, >should you correct for effects of interest only for that single session, >or for all the sessions in your design matrix? > >And what are the various implications and assumptions of making these >different types of correction? >with thanks >Chris Summerfield and Julie Grezes > > > >Christopher Summerfield >[log in to unmask]