Dear SPMers,
I am working on an analysis of a PET activation study (8 subj, 2 cond, 3
repl).
Multi-subject: conditions x subject interaction model was chosen
and two contrasts were used for generating SPM maps.
Contrast1: 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1
Contrast2: p1 -p1 p2 -p2 p3 -p3 p4 -p4 5 -p5 p6 -p6 p7 -p7 p8 -p8
Where pi the mean of an electro-physiological parameter of ith subject
(these parameters were measured during all PET scans)
These parameters were also used as indicators of the subjects in the
subject selection procedure.
The result given by Contrast2 was better then Contrast1:
the t-values of cluster-maximums were higher and
the sizes of clusters were larger.
My questions are:
- Is the Conrast2 correct? (as factorial approach)
If it is:
- Can we say that the activation of these clusters have a parameter-dependent
augmentation?
Many thanks in advance
Miklos
