Dear SPMers,
I have some questions concerning PPI analysis.
I tried to find the brain area correlating with TPJ, modulated by the psychological variable (other vs. self)
I used the other-self contrast in "spm.mat" to extract the VOI.
Then, I used the same SPM file to generate the PPI variables accroding to other-self contrast weight.
The point is ...
Is it ok to use the same contrast weight from the same "spm.mat" file during both extraction of VOI
and generation of PPI variable?
Actually, I have done the analysis already.
And I checked the colinearty between PPI-interaction regressor (column 1) and
Psychological variable regressor (column 3) from the design orthogonality menu in SPM8.
I can not find any colinearity for each participant.
However, I might be worried about the concept of PPI analysis.
So, Could you please tell me whether the analysis I have done so far is correct or not?
|