Dear Rafael,
We had the same issue a few months ago and the following discussion
helped us to understand what was going on:
https://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0702&L=SPM&P=R5143 . You
could also have a look at this part of the answer :
https://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0702&L=SPM&P=R7112
I Hope this helps,
Camille
--
Camille MAUMET
Unité/Projet VisAGeS U746
IRISA-INRIA Rennes
Campus de Beaulieu
35042 Rennes Cedex
France
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Rafael Lüchinger wrote:
> Dear SPM users
>
> I want to compare neuronal activation (positive contrast) and deactivation
> (negative contrast) between two groups. In my analysis both the positive as
> well as the negative contrast is of interest (1st-level con.imgs as [1 0
> ...] and [-1 0 ...] respectively).
>
> I realized that comparing the two groups [1 -1] in terms of positive
> contrast is the same as comparing the two groups the other way around [-1 1]
> based on negative contrasts. This is not good. I want to see both group
> comparisons (A<B and A>B) separately for the activation maps and
> deactivation maps respectively. This should result in 4 different results.
> Why is there this redundancy?
>
> How can I test the two groups for differences in the activation maps and
> deactivation maps separately?
>
> May the fog burns off due to your wellcome input
>
> RL
>
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