Mauro -
> The problem is, as Matthew correctly points out, that people (1) tend
> to shorten the statement to "area X is activated by task A" and (2)
> may go beyond the data concluding "area X differs from area Y for
> task A". Concerning (1), authors should change their habits (make
> their constrats really explicit and avoid incomplete statements) and
> reviewers shouldn't accept fuzzy statements.
Absolutely. More convincing evidence for your claim (2) would be a
Region-by-Condition interaction (ie, gets round thresholding effects
on the two "simple effects" in regions X and Y).
[In fact, I think there are a few more criteria too, which if you are interested,
are spelled out in:
Henson, R.N.A. (2005). What can functional imaging tell the experimental
psychologist? Quarterly Journal of Experimental Psychology, A, 58, 193-233.
(let me know if you want a copy)].
Such interactions with Region cannot be tested in SPM, which is a mass univariate
approach (ie space is itself not "factorised"). It is easily done if you extract the
data for a few ROIs. What would appear slightly more complicated is to test such
interactions over the whole brain (i.e, how to factorise all voxels). Here multivariate
approaches may be more fruitful.
Rik
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Dr Richard Henson
MRC Cognition & Brain Sciences Unit
15 Chaucer Road
Cambridge
CB2 2EF, UK
Tel: +44 (0)1223 355 294 x522
Fax: +44 (0)1223 359 062
http://www.mrc-cbu.cam.ac.uk/~rik.henson
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