 |
 |
Hi Steve, thank you for the reasurrance that my designs are ok. However, I am still confused about the contrast masking. As I mentioned previously I have read the manual and also other postings on the issue, but remain confused and was hoping you could clarify. For example I want to look at Pre (Left > Right) Vs Post (Left > Right). I therefore want to know where the Pre group had greater activation than the post group when looking at Left vs Right. so if I assume that if I have the contrasts C1 = Pre (left>right) C2 = Post (left>right) C3 = Pre>Post C4 = Post>pre would I contrast C3 with C1 AND C2? And then do the same for C4? I am unsure as to when I contrast with one or both masks. And presumably if I use the Z>0 I am only looking at positive activation? Is this correct? Thanks in advance for any clarification and I again apologise for my basic understanding of analysis. Rebecca On Wed, 11 Mar 2009 06:37:15 +0000, Steve Smith <[log in to unmask]> wrote: >Hi, > >You can certainly run any contrasts between these groups with FEAT, >but I'm still not sure in what way it makes sense here to use the >controls, given that you didn't also give them the treatment. You can >run the following contrasts that make some sense: > >controls-patientsPRE (unpaired t-test model) >controls-patientsPOST (unpaired t-test model) >patientsPOST-PRE (paired t-test) > >See the FEAT manual for example models. >Hopefully this will give you the results you need? > >Cheers. > > > >On 10 Mar 2009, at 08:30, Rebecca Leigh wrote: > >> Hi Steve, >> sorry I should have been clearer about my groups. >> >> My controls are healthy volunteers, my training group consist of >> patients. >> I therefore want to examine how patients differ to healthy controls >> prior to >> training and how they differ after training. >> Do my FEAT analysis seem reasonable if this is what I want to examine? >> > > >-------------------------------------------------------------------------- - >Stephen M. Smith, Professor of Biomedical Engineering >Associate Director, Oxford University FMRIB Centre > >FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK >+44 (0) 1865 222726 (fax 222717) >[log in to unmask] http://www.fmrib.ox.ac.uk/~steve >-------------------------------------------------------------------------- -