Hi Valentina,

This may be perhaps caused by the age variable not being centered?. To clarify, when controlling for age in a single-group analysis you need to specify the age-level at which you would like to estimate your effects (e.g. average connectivity). Often one selects the average age in your sample as the reference age-level, which is typically accomplished by centering the age variable (subtracting its mean) before entering it in your second-level analysis. 

In CONN you can do this for example by first going to 'Setup.Covariates (2nd-level)' and creating there a new "AgeCentered" variable. In the 'values' field of this new AgeCentered covariate you may enter the formula "age-mean(age)" without quotes, so that it is not necessary to calculate those centered values elsewhere/explicitly. Then enter in your second-level model the effects 'AllSubjects' and 'AgeCentered' and select the same [1 0] contrast to evaluate the average connectivity at the zero-level of your AgeCentered variable (which corresponds to the average age within your sample).

Hope this helps

Alfonso

Originally posted by Valentina Meregalli:

Hello Alfonso,

I'm following up on this post because I have a question about controlling for age within a single group of patients in a seed to voxel analysis. What I have done so far is to include the following contrast: Group, Age [1,0]. However, I noticed that nearly all the effects I observed without controlling for age disappear. I wanted to ask if this approach is correct, or if it would be better to use another strategy or not control for age at all?

Thank you, 

Valentina