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Thanks so much for your thoughtful response! sincerely, Chris Hardy Catalyst Agency LLC [log in to unmask] On Thu, Feb 11, 2016 at 1:48 AM, Anderson M. Winkler <[log in to unmask] > wrote: > Hi Chris, > > Please see below: > > > On 11 February 2016 at 00:20, Chris Hardy < > [log in to unmask]> wrote: > >> Hey FSLers, >> >> I have a multi-session question, for which I could not find an exact >> answer in the archives nor the multi-session / repeated measures example >> given in the documentation: >> http://fsl.fmrib.ox.ac.uk/fslcourse/lectures/practicals/feat2/index.html#multisession >> , although it is closely related to the example. >> >> Specifically, for each subject, I have three different conditions (A, B, >> & C), and each is it's own entire functional session (one run for A w/ no >> other EVs, one run for B and no EVs, etc). I simply want to end up with >> the group level copes A-B, B-C, & A-C. Judging from the example, I should >> run 3 levels of FEATs (since there is no multi-session functionality built >> in): >> 1) 3 separate FEATs for each subject - 1 for each session - and make a >> 'contrast' that is just 1 for the one regression since there's nothing to >> subtract against. This essentially is asking if the parameters measured >> are greater than 0. >> 2) a FEAT within each subject using these 3 1st level FEATs to create the >> contrasts. >> 3) a group-level feat >> >> Essentially just a paired t-test where the variables are different >> session blocks. >> > > Yes, everything fine until here. Note that the multi-level in FEAT is > precisely for multi-session, so there is a such built-in functionality. At > any rate, please see below: > > >> >> My concern is that upon following this logic and running the level 1 for >> each subject is that my A-nothing contrast showed no significant voxels, >> but it seems like there absolutely should be, given the person was alive. >> > > Subject living or not, there may be no significant activity, even with a > simple contrast as this. This isn't really a problem. > > A suggestion is to continue with the analysis. It may well be that none or > very few of the subjects actually display activity, but at the group level, > some results may be seen (or still not). > > >> >> Previously, I had tried concatenating the runs into one functional, and >> then having A, B, and C in each subject's initial model, but from what I >> can tell about FSL (I come from SPM), that creates issues with movement b/n >> sessions and temporal filtering problems. >> > > Exactly. > > All the best, > > Anderson > > > >> >> Thank you for any input! >> >> >> sincerely, >> >> Chris >> > >