Most of my participants have 2 resting state fMRI files. There are two time points (pre and post), thus most participants have a total of 4 files/4 sessions. However, there are a few participants who have only 1 resting state fMRI file for a time point instead of 2. For these "1 file instead of 2" participants, they have the same amount of data as the 2 file participants (the total number of slices is the same, it's just in one file). I know that I can adjust the amount of sessions for each participant when setting up the design in CONN, but how can I tell CONN that the two post files are really post, because they will labelled as 2(pre2) and 3(post1).

For example, let's say sub 01 has 4 files. Pre has two files assigned to it (sub_01_pre1; sub_01_pre2) and post has the same amount (sub_01_post1; sub_01_post2). Sub 02 has 3 files. 1 file for pre (sub_01_pre) and 2 files for post. When I look at it in CONN, sub 02 now has 3 sessions, and the two post sessions are now session 2 and 3, when they should be 3 and 4. Do I treat session number 2 as 'missing?' or is there a better way to go about this?

Thanks for you help,
Brian