Hi SPMers,
as I am quite new to SPM, I am, once again, in desperately seeking advice....
I am trying to set up a PPI-analysis for multi-session data. Our experiment consists of four runs, each comprising 338 scans (total 1352). In order to set up the PPI-analysis and not to concatenate the sessions; I followed Darren Gitelmans instructions in
https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind06&L=spm&P=R380429&1=spm&9=A&I=-3&J=on&d=No+Match%3BMatch%3BMatches&z=4
Everything worked out fine, except that in the multiple regressions analysis SPM did not accept the covariate vectors for the single sessions. My guess was, that that was the case, because each vector had 338 digits only (single session). So my idea was to pad the vectors with zeros for the images of the other runs (eg. for session one: ["vector"; zeros(1014,1)], session two: [zeros(338,1); "vector"; zeros(676,1)],...).
So far, this analysis did run, but produced a lot of activated clusters outside the brain, in CSF,... So finally, my question ist, whether this procedure is valid????
Any help would be appreciated!
Thanks,
Dorrit
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