Hi Yifei,

Regarding your first question, that was a gui-bug which affected the display of the second-level covariates (but not the actual values used in the analyses). The last version of the toolbox (14a) that I just uploaded includes a fix for this issue.

Regarding your second question, you are right that if you want to perform a two-sample t-test controlling for age, you would select the 'HC', 'AD', and 'age' effects, and then enter a between-subjects contrast [1 -1 0]. This gives you differences in functional connectivity between the two groups controlling for potential age-differences between these two groups of subjects.

Last, for one-sample t-tests, if what you want is to show the average connectivity within each group "at the same age level" (despite potential differences in age between the two groups), you need to first create two new second-level covariates: one, named 'ageHC' for example, that contains the age of the HC group subjects and 0's for the AD group subjects; and a second, named 'ageAD', that contains the age of the AD group and 0's for the HC subjects. Then you would select 'HC', and 'ageHC', and enter the contrast [1 0] (and equivalently for the AD group). Note that it is typically important that in your second-level covariates you enter the age values after 'centering' (e.g. take the ages of ALL of your subjects and subtract their average). This is important because the zero-value of your 'age' covariate will be the age level at which you will be estimating the connectivity in your age-controlled one-sample t-tests (e.g. if the average age across both groups is 30, and you subtract 30 from the actual age values entered into the ageHC and ageAD covariates, then you can interpret the one-sample t-test results as the expected connectivity strength within each group at age 30)

Hope this helps
Alfonso


Originally posted by Yifei Zhang: