No - that's fine - just consider them as if they were different conditions
at the group level - then you can compare them. I hope this makes sense!
Thanks, Steve.
On Wed, 16 Oct 2002, Tracy L. Luks wrote:
> OK, but what if my different EVs don't mean the same thing, and I
> specifically want to compare them? For example, we have an experiment
> in which subjects attended to different spatial locations in each
> run, so that an attention cue in run1 meant Attend Left, but in run2
> meant Attend Right. It seems to me that the only valid way to compare
> them is to include all conditions in the same first-level analysis.
> Is there another way?
>
> Thanks,
> Tracy Luks
>
>
> >Hi - not quite - in fact _theoretically_ one of the strengths of
> >multi-level FEAT analysis is that it is not necessary for the first-level
> >designs to be the same.
> >
> >In practice, as long as all the cope images that you input to the
> >second-level analysis MEAN the same thing (ie asked the same question at
> >first-level) then it doesn't matter whether irrelevant EVs were present at
> >first-level. For example, if cope1 always means "VISUAL-REST" at
> >first-level then the second-level analyses will make sense....
> >
> > Thanks, Steve.
> >
> >
> >On Tue, 15 Oct 2002, Tracy L. Luks wrote:
> >
> >> Hi,
> >>
> >> I'm interested in using fsl to analyze fmri data from an
> >> event-related study in which subjects performed multiple runs of two
> >> different task conditions (i.e. runs not only have different timing,
> >> but some different EVs). I understand that in order to use the
> >> three-level analysis approach, the second level analysis assumes that
> >> the EVs of the first-level design matrices are identical. Is there
> >> any other way to examine effects of these different EVs within
> >> subjects?
> >>
> >> Thanks,
> >> Tracy Luks
> >> --
> >> ********************************************************************
> >> Tracy L. Luks Ph.D.
> >> Dynamic NeuroImaging Lab
> >> University of California San Francisco
> >> [log in to unmask]
> >> Office: 415-514-2527
> >> Cell: 650-219-6927
> >> Home: 415-459-5046
> >>
> >
> > Stephen M. Smith
> > Head of Image Analysis, FMRIB
> >
> > Oxford University Centre for Functional MRI of the Brain
> > John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
> > +44 (0) 1865 222726 (fax 222717)
> >
> > [log in to unmask] http://www.fmrib.ox.ac.uk/~steve
>
>
> --
> ********************************************************************
> Tracy L. Luks Ph.D.
> Dynamic NeuroImaging Lab
> University of California San Francisco
> [log in to unmask]
> Office: 415-514-2527
> Cell: 650-219-6927
> Home: 415-459-5046
>
Stephen M. Smith
Head of Image Analysis, FMRIB
Oxford University Centre for Functional MRI of the Brain
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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