Dear SPM experts,

 

In my experiment I have 4 sessions with 3 runs and two conditions of interest per subject. I’m interested in the condition x run interactions within session and across sessions. I want to set up the first level analysis in a way that I can do statistical tests of all interaction effects on the second level with one-sample t-tests. I’d appreciate your help with respect to setting up the interaction contrasts:

 

1) Are these contrasts correct?

 

(across-)run (12) x condition (2) contrast (linear increase of condition A>B)

[1,-1; 9/11,-9/11; 7/11,-7/11; 5/11,-5/11; 3/11,-3/11, 1/11,-1/11; -1/11, 1/11; -3/11,3/11;-5/11,5/11; -7/11,7/11; -9/11,9/11; -1,1]

 

Within-session run (3) x condition (2) contrast (linear increase of condition A>B)

[1,-1; 0, 0, -1, 1; 1,-1; 0, 0, -1, 1; 1,-1; 0, 0, -1, 1; 1,-1; 0, 0, -1, 1]

 

2) How to build the session (4) x run (3) x condition (2) contrast? Do I just need to add the two interaction contrast vectors above?

 

Your help is much appreciated!

 

Chris