Dear Freesurfer experts,
I am modelling multiple covariates (age, SES, nr of symptoms and nr of symptoms2) in one subject group. For the quadratic term I added a column in the fsgd-file. I want to visualize the effect of nr of symptoms, either their linear or their quadratic effects. I therefore made two contrasts:
The effect of symptoms:
0 0 1 0
And the effect of symptoms2:
0 0 0 1
I would like to model these two effects together in one contrast (to get the results of both contrasts overlaid on top of each other, but in one mgh file). I tried the following contrast:
0 0 1 0
0 0 0 1
But the result is very different from the two individual contrasts. I get large (non-overlapping) clusters of significant effect in the two separate contrasts, but with the combined contrasts I get none. In the examples I found online for F-contrasts, they always add up to zero, as they are comparisons between groups. What would be the appropriate contrast if I want to visualize all regions with EITHER a linear OR a quadratic effect of symptoms?
Thank you very much for your help!
Best wishes, Lizanne