Hi Alfonso,

Thank you for your quick response! I just want to confirm my understanding:

I need to create an age-centered variable separately for patients and controls, based on their respective mean ages (since patients are slightly younger than controls). Then, I ca perform two separate within-group analyses to investigate the seed-to-voxel connectivity of my ROIs in each group. Finally, to assess group differences, I use the original (non-centered) age variable and set the contrast as follows: patients = 1, controls = -1, age = 0. Does this approach sound correct?

Additionally, I have a clarification: if I want to assess the influence of a cognitive variable on connectivity in the patients group only while controlling for age, should I use the age-centered variable or the original age variable?

Thank you again for your time and guidance!

Best regards,
Valentina