Bjorn,
> I am using SPM99, I also have wfu_pickatlas and marsbar installed.
> I have a study with four conditions including baseline, and we are
> interested in knowing which areas are activated in all cases realtive to
> the baseline. So something like this:
>
> (C4>C1) /\ (C3>C1) /\ (C2>C1)
>
> where /\ is intersection.
> (actually, we are interested in confirming that a particular region is
> activated in all these regions, so we are restricting our analysis to a
> particular ROI, in case it matters).
>
> It seems the right way to do this is to select the three contrasts (which
> represent C4>C1, C3>C1 and C2>C1) in the results section. Assuming this is
> right, I am not sure what to say in response to spm's question "Null
> Hypothesis to assess". The options are "Conj'n," "Intermediate," or
> "Global". Will "Global" give me the intersection of these contrasts? Am I
> way off base? Also, does the orthog. order really matter? Thanks in
> advance!!!
If you would like to conclude that the effects corresponding to
all three of these contrasts are simeltaneously "real", then you
want to use the "Conj'" null.
Regarding orthogalization, *yes* order does matter. But note
that no orthogonalization is needed with the use of Conjunction
Null.
For more, see http://www.sph.umich.edu/~nichols/Conj and the
two articles on Conjunctions on the "In Press" section of
NeuroImage website.
-Tom
-- Thomas Nichols -------------------- Department of Biostatistics
http://www.sph.umich.edu/~nichols University of Michigan
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-------------------------------------- Ann Arbor, MI 48109-2029
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