Dear SPMers,
 
to test whether there is any difference (i.e. irrespective of the direction of signal change) between two conditions, is it valid to do an F contrast like this:
 
[-1 0;
  0 1]
 
?
 
...and extending this to two sessions (repeated conditions) in one design (let's assume, there are only 2 conditions/colums per session):
 
[-1 0;
0 1;
0 0 -1;
0 0 0 1]
 
?
 
It looked straight forward to me in the first place, but now I am confused.
 
Any help appreciated.
 
Thank you.
 
Helmut