Hello! 

I realize this is an older post but I am trying to run this same type of analysis and I have not found answers on this forum yet.

Is the correct contrast for analyzing the effect of age on connnectivity within a group: Select GroupA and Age_GroupA and use the contrast [0, 1] ?

Should Age_GroupA be mean-centered, and if so, do I use AllSubjects or GroupA to center it?

Thank you for any and all clarification!

Best,

Madison