Hi Xuehu,

You may want to check out some of the other posts on this forum that discuss the design matrix for longitudinal designs.

In brief, your design matrix would comprise:

1. A separate column for each subject. Each of these columns would include two ones corresponding to the two visits for that subject, while all other entries would be zero

2. A single column of ones and zeros indicating the time of visit (first=0, second=1)

3. An additional column for language score

4. The interaction between language score and time. You would element-wise multiply Columns 2 and 3 to get the interaction term. Note that you would need to remove column 3 if you want to study the interaction.

Another approach is to simply subtract structural connectivity at the first visit from structural connectivity in the second visit. You could then run the NBS on the DIFFERENCE in connectivity. This can be done with a simple design matrix comprising the language score (or it difference) and a column of ones.

Andrew


Originally posted by Xuehu Wei: