Hi SPM community,
this is a test set up question following up on previous responses.
Assume the following experiment design: block, one task, 2 sessions, 12 participants, one
custom regressor (R) that models the changing stimulus intensity of the task.
First level Analysis:
I have the following questions:
(1) Is there task related activity? I am setting this up as shown in the attached diagram
with a '1' for the task and all zeros for the rest of the parameters.
(2) Does the addition of the custom regressor (R) change my activation? That's a more
tricky question and I am not quite sure about it. Should I set that one up as a '1 1
followed by zeros' - contrast or a '0 1 followed by zeros' - contrast?
Alternatively, should I run 2 models, one including the custom regressor 'R' and one
without it and I am getting two .mat files in my 1st level analysis, how do I then set up
my model comparison in SPM? I understand that comparing nested models would be an F-
test, but how do I enter two .mat files in the contrast manager?
(3) If I figured out the proper way at the subject (1st) level, how do I use this information
at the second level. Presumably, this depends on the approach at the first level.
Thanks for you help and I hope this will be of interest two others.