Hi Alfonso,

I have been using Conn for a few months, it is an amazing tool, thank you!
I have 2 questions regarding the "Between-subject contrast" in the Seed-to-Voxel analysis.
I have noticed that for comparisons between 2 groups ("patients" and "controls"), I can see some obvious visual differences in the Result previews when I select "Any effect (F-test)" in Between-subject contrast (image attached, subjects on the right). It seems like there is an obvious decreased connectivity in subjects compared to controls.
However, I don't find the same result when I compare patients and controls (Patients>Controls in Between-Subject contrast) with only small area of increased connectivity in patients.
What is the test performed if I select 2 groups and "Any effect" as between-subject contrast (in the result explorer box)?
Why the visual differences found when selecting "Any-effect" are not found when I select "Patients>Controls" in Between-Subject contrast? Do you think it could be due to insufficient statistical power?

Thank you very much for your reply!

Mickael Tordjman

Hi Mickael,

The "Any effect" contrast when selecting two subject-groups simply highlights those regions showing significant connectivity with the seed ROI in any of the two groups (i.e. Patients≠0 or Controls≠0), while the "Patients>Controls" contrast will highlight those regions showing significantly different connectivity strength between the two groups (i.e. Patients≠Controls). It is perfectly fine/common to observe "differences in significance" (e.g. an effect is significant in one group but it is not significant in a second group) that are not truly "significant differences" (e.g. the between-group differences is not significant)

Hope this helps
Alfonso
Originally posted by Mickael Tordjman :

Great, thank you very much for your reply!

Best,
Mickael