Hi all

can you please let me know if there is a difference between these two cases:

1- making two contrast images in the first level using the contrast 1 or -1. Then taking the negative contrast images to the second levels for all subjects and perform a one sample t tests

2- making just one contrast images in the first level using the position contrast 1. Then taking the con images to the second level, performing a one sample t test and doing a negative contrast. 

In other words do I have to defined the negative contrast at the firstly level? 

Thanks

Aser