Hi Peter,
thank you very much for your (always) very helpful response!
I think I understood what you meant but just to be sure, can I ask you two other questions?
In your response you wrote "I would drive the DCM using just the active condition (leave the passive unmodelled)", but I thought it is not a good idea to leave conditions unmodelled. In this post https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=spm;555aca73.1803, you seem to recommend modelling everything in the DCM, or did I misunderstand?
If I decide to go for the more efficient modelling, should the my design matrix look like this for the active condition?
emot vs neu active PM(emot vs neu active) pos vs neg active PM(pos vs neg active)
Pos 1 Pos 1
Neg 1 Neg -1
Neg 1 Neg -1
Pos 1 Pos 1
Neu -1
Neu -1
Pos 1 Pos 1
... ... ... ...
where Pos,Neg and Neu are the onsets for those valence types, and PM the parametric modulator. I would have 4 columns in total (emot vs neu active, pos vs neg active and their corresponding parametric regressors). Or should I still include the passive condition in the design matrix (emot vs neu passive, pos vs neg passive and their corresponding parametric regressors), in which case I would have a total of 8 columns?
Thank you for your help!
Best regards,
Sam
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