Dear
SPM'ers,
to
complement Marco question, I would propose an alternative way, but I am not sure
if it is fully correct :
1) at
1st level, compute separately every individual contrasts lets say A : [Cond1 vs
Cond2] AND B : [Cond3 vs Cond4]
2)
forward the resulting A and B *con*.img at the 2nd level using Basic models --
multiple regression without the constant term design
3)
estimate the effect of A inclusively or exclusively masked by
B
Practically, it works (SPM propose the masking option) , but
theoretically ? Did the SPM experts agree with the procedure ?
Philippe Peigneux
Dear SPMers,
there have been a couple of similar questions on
this topic a while ago:
but I couldn't find no clear answers to
them.
I also would like to perform some masking of
contrasts at a second level RFX analysis. Could someone please specifiy
whether the following procedure is correct:
1) At the first level, compute for every single
subject the statistical map of say contrast x (Condition 1 vs Condition 2)
masked with contrast y (Conditions 3 vs Condition 4).
2) Write filtered the maps obtained by step
1.
3) Perform a second level RFX analysis (e.g.
one-sample t-test) on the images obtained by step 2.
Thank you a lot for your help!
Best wishes,
Marco Tettamanti
Istituto Scientifico San
Raffaele
Medicina Nucleare
Via Olgettina 60
I-20131
Milano
Italia
tel. 0039 - 02 - 26 42 34 60
fax. 0039 - 02 - 21 71 75
58
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