Dear SPM list:
We are performing a VBM analysis on gray matter tissue from two conditions
C1; control; C2; disease
For the two groups. we have a categorical covariant named "S" (1=male.
2= female).
Our goal is to see whether S interacts with condition to make the
results different
We used a "single subject conditions and covairates" model
We selected 2 conditions (C1, C2) and one covariate (S)
We then got a contrast matrix as attached figure
There are four columns of the matrix
1#= condition 1
2#=condition 2
3#= sex@ condition 1
4#= sex @ condition 2
we think
1, -1, 0, 0 = difference between C1-C2
but what is
0, 0, 1, 0,
0. 0. -1. 0
and
1. -1, 1, 0
We are quite puzzle about the interpreation.
Please help, thanks
Sincerely
MT Wu
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