Hi - some short questions:
1. We analyzing data from a multicenter study. To analyze data at a group level, we included an additonal covariate to model the effect "center". Each subject from center 1 got a "1", from center 2 a "2" and so on. Is that the right way?
2. To compare patients and control we used a paired t-test. Each pair consisted of a patient and his/her matched control. In the contrast "patients > controls" we found activation differences in the amygdala. To find out why these differences exist (Both groups show activation, but the patients show more activation? The patients show activation, but the controls deactivation? Both show deactivation, but the controls more deactivation?) I would normally define an additional F-contrast "Effect of interest" ([1 0; 0 1]) and look at the parameter estimates. SPM does not allow me to do that? Why is it not possible in paired t-tests?
3. When I looked at the con-, ß-, and t-images underlying the activagtion, I noticed something that looked peculiar to me: at the local maximum coordinate, there was a NaN entry in the ß-images, the con-image and the ResMS-image, but a normal number in the t-image. Since the t-image is calculated using the other images, I would be interested in understanding this phenomenon.
Best wishes
Henrike
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