Yes that makes complete sense. However, it does not work for how I've set up my contrasts and the effects I'm looking for - are there any other ways?

Thanks!!

Eugene Duff wrote:

If you want to limit you results to regions where, say, the first regressor was associated with a positive response, you can use contrast masking.  Select contrast masking in the post-stats section and input the contrast where you tested for a positive response in that condition (e.g. the 1 0 contrast).  Selecting "Mask using z>0.. " makes the masking less severe, showing regions where the fit of the regressor was positive, but not necessarily significant.
I hope that makes some sense!
Eugene

2009/5/18 Vina Goghari <[log in to unmask] <mailto:[log in to unmask]>>

   Thanks for your response. What is the way to ask for activations > 0?

   Thanks!

   tEugene Duff wrote:

       Hi Vina,

       2009/5/18 Vina Goghari <[log in to unmask]

       <mailto:[log in to unmask]> <mailto:[log in to unmask]

       <mailto:[log in to unmask]>>>


          Hi,
          A couple of quick questions about when setting up contrasts:

          (1) If you have two regressors that at a lower level you
       set up:
          R1 0 1
          R2 1 0

          And then you contrast: -1 1. Do you still have to be
       worried that
          the contrast could stem from a difference that is below
       zero for
          both regressors?

       If I understand you correctly, then yes, this contrasts would
       identify differences in responses even if they are all
       negative responses (deactivations).             (2) When you have three groups can you set up your higher level
          contrast this way to sum 0 (1 1 -2)?

       This contrast will find regions where the responses modelled
       by the first two evs are significantly greater than those
       modelled by the third EV.  These regions may not necessarily
       remain signficant when only one of the first two evs is
       contrasted with the third.
       Best
       Eugene
                  Thanks!




       --
       Eugene Duff

       FMRIB Centre,
       University of Oxford
       John Radcliffe Hospital, Headington OX3 9DU  Oxford  UK

       Ph: +44 (0) 1865 222 739  Fax: +44 (0) 1865 222 717

       --




--

Eugene Duff

FMRIB Centre,
University of Oxford
John Radcliffe Hospital, Headington OX3 9DU  Oxford  UK

Ph: +44 (0) 1865 222 739  Fax: +44 (0) 1865 222 717

--