Dear Thomas,
> we have a question regarding the contrast setup for the fmri statistic:
> Our experiment has 3 Conditions: Rest, Stim1 and Stim2.
> We build contrasts like this:
> C1: -1 1 0 to see effects of Stim1 against Rest condition
> C2: 1 -1 0 to see negative effects of Stim1 against Rest
> C3: -1 0 1 to see effects of Stim2 against Rest condition
> C4: 1 0 -1 to see negative effects of the above
> C5: 0 1 -1 to see effects of Stim1 that can not be explained through
> Stim2.
>
> Now the question:
> Does contrast 5 give me the areas activated by stimulus1 that are not
> activated by stimulus2 ?
More exactly it shows areas that are activated by stimulus1 relative
to stimulus2. Areas that are 'more' activated by stimulus1 implies
that both stimulus1 and stimulus2 activate relative to rest. These
areas would be identified by the conjunction (or masking of) C5 with
C1 and C3.
> How can I see the negative effects corresponding to contrast5 ?
Simply use
C6: 0 -1 1
With best wishes - Karl
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