Dear SPMers,
a small question on DCM.
Let's suppose that I have the visual stimulation consisting of neutral
and fearful faces
and I want to assess the modulation of fear on a given connection.
In the design matrix I would put a column with all the faces (fearful
and neutral)
(this would be u1 in the term Cu1), and a second
column with just fearful faces (this would be u2 in the term
Bzu2).
But someone instead suggested to me to put in the second column a
parametric modulation (SPM.sess.U.P) with ones corresponding
to onsets of fearful faces and -ones corresponding to onsets of neutral
faces?
Is this correct, better, or the same?
Thank you very much.
Best,
iole
