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HC You might want to try some noise reduction techniques - including motion parameters in the model, improving registrations, ICA denoising etc. Cheers, Eugene -- Centre for Functional MRI of the Brain (FMRIB) | University of Oxford John Radcliffe Hospital | Headington OX3 9DU | Oxford | UK Ph: +44 (0) 1865 222 523 | Mob: +44 (0) 7946 362 059 | Fax: +44 (0) 1865 222 717 -- On 18 November 2010 07:48, Stephen Smith <[log in to unmask]> wrote: > HI - this is indeed the generally recommended approach - however, IF the > trend is truly linear then you will get a slightly more sensitive analysis > having only one EV (or one for mean and one for slope). Your residuals will > go up (unless things are perfectly linear), but so will your degrees of > freedom. I'd be surprised though if this makes things better. > Cheers > > > On 17 Nov 2010, at 21:04, HC wrote: > > Hello experts! > > I have a design in which I have 4 levels of a treatment: 1, 2, 3, and 4. I > predict that signal should be a monotonically increasing function with 1 > having the lowest signal and 4 having the greatest. What is the best way to > set up my EV files to test this? > > In the past, I have tried 1 EV per treatment level, and then used a contrast > of : > > level 1 level 2 level 3 level 4 > -3 -1 1 3 > > But this method seems to not be quite sensitive enough to detect the effect. > Any other suggestions? > > Thank you in advance for your help! > > > > --------------------------------------------------------------------------- > 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 > --------------------------------------------------------------------------- > > > >