Dear Cyril and Helmut,
I proceeded to do the following contrasts at both the first and second timepoints.
1) LR - L – R aka [ 1 -1 -1 0]
2) (LR + REST) – (L + R) aka [1 -1 -1 1]
3) (LR – L) ∩ (LR – R) aka select both [1 -1 0 0] [1 0 -1 0]
There is little to nil activation in all contrasts for both timepoints... except for a very bizarre result for contrast 1 at the second timepoint. I have attached 3 screenshots: for contrast 1 at both timepoints and LR-REST.
How is it possible that contrast 1 at timepoint 2 yielded so much more activation than LR-REST? I have re run the entire analysis 3x. Other contrasts appear to make sense except for this.
Additionally, all these contrasts seem to show over-additive effects. How do you show under-additive effects? In my experiment, I'm trying to map out how different if any (whether more or less) LR is to sum of L and R.
Thanks!
Pei Ling
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