Hello fellow SPM users,
With some investigation into con images, my lab found that con images appear to be sums of the beta images that one specifies depending on the weight that is assigned (i.e. 1 0 0 0 0 1 0 0 0 0 - you would add the two beta images together). This appears to be the way it is calculated instead of a mean value. So does SPM account for the fact that subjects will have varied block counts, such as one subject having 5 sessions and another having 2 sessions? Or is the subject with 5 sessions going to contribute 2.5 times as much at the group level as the subject with two sessions? For it to be valid, does one have to put in a contrast vector like 1/5 0 0 0 0 1/5 0 0 for the 5 session subject and 1/2 0 0 0 0 1/2 0 0 for the 2 session subject?