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> Why don't you want to get ts with variance related somehow to your task(s) and regress out effects of no interest? Yes I agree - it does seem odd to want to regress out task-related variance Steve On 27 Aug 2011, at 20:32, Dr I.J. Bohr wrote: > There are a couple of points remaining here: > > 1. weights for F-contrast (unlike T-contrast) are defined as a matrix with as many rows as effects of interest (eof): ones attributed (you compare everything with everything else in both direction, so all significant variance related to these regressors is extracted. > > 2. what is the point of defining constant term as your eof, it's just a scalar: mean signal for the whole session, so there is no variance there at all? > > Why don't you want to get ts with variance related somehow to your task(s) and regress out effects of no interest? > > Iwo > > On Aug 27 2011, Steve Fleming wrote: > >> Hi Peter, >> >> Yes I think for your purposes it would be the latter (zeros(1:11) 1). >> As Iwo pointed out, the "adjust data" option removes the null space of your F-contrast, i.e. the zeros, from your timeseries. See lines 143-153 in spm_regions. >> >> Hope that helps >> >> Steve >> >> On 27 Aug 2011, at 19:11, Peter Michalsky wrote: >> >>> Hello Iwo, >>> first let me thank you for your reply. You understood correctly that I want to regress out all nuissance factors while extracting a time-series from a VOI. However, I also want to regress out the task variance (first two regressors in the design matrix). Hence, I want to regress out all 11 regressors and only keep the mean time-series. Do I do that by ones(1:11) zeros(12) or by zeros(1:11) ones(12). If I understood you correctly the correct solution should be to define an F-contrast with all zeros except for the constant (zeros(1:11) 1). Maybe you could explain to me why the opposite (ones(1:11) 0), which I thought would be right is wrong. Thanks again for your help. >>> Peter >> >> ____________________________________ >> Stephen M. Fleming PhD >> Wellcome Trust Postdoctoral Fellow >> http://web.me.com/stephen_fleming/web/Welcome.html >> ____________________________________ Stephen M. Fleming PhD Wellcome Trust Postdoctoral Fellow http://web.me.com/stephen_fleming/web/Welcome.html