Dear SPM users,
There have been questions similar to this posted in the list before, but I have doubts on a particular point I hope someone might clarify further.
I have a group of subjects where I want to compare activation in response to tactile stimulation before and after a treatment. Thus I have two identical sessions per subject. In each session there is only one condition (stimulation) which is contrasted to baseline. The design is a simple block design with blocks of 32 seconds.
I want to enter the two sessions in the same 1st level design for fixed effect analysis. When I do so I get a matrix where the first two columns represent a session each (see attachment). How then would I indicate when doing the contrast that I want to look at that effect (stimulation dependent activation) for that session? In other words
(stimulation pre - baseline pre) - (stimulatin post - baseline post)
Is that what I am getting if I enter the vectors 1 -1 0 0 ? For a single session I would just use  as vector for that contrast (stimulation - baseline). In this case however, that within-session contrast is not specified.
For the sake of clarification, let us say I wanted to look not at activation but deactivation during stimulation. For a sinlge session the vector would be just [-1], right?. How then would I compare deactivation between sessions?
Would it make sense to enter the rest periods as another condition? In that case, what would the contrast vectors look like?
Many thanks in advance.