Dear Haakon
I am not aware of any issues with having disconnected nodes (but then again I've never tried it!). You don't mention why you want this - it's quite a strong hypothesis to say that two brain regions have no effective connectivity, but you may have good reason for that.
Note that if you're using the basic (deterministic) task-based DCM for fMRI, then you'll have no dynamics in disconnected regions unless they receive driving inputs.
Best
Peter
-----Original Message-----
From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]] On Behalf Of Haakon Engen
Sent: 31 May 2018 17:11
To: [log in to unmask]
Subject: [SPM] Unconnected nodes in DCM A matrix
Hi again all,
I’ve a question regarding A matrix specification. I’m running a 4 node DCM with a bunch of models, separated into families with different A-matrix setups. In some of these models, one or two nodes are “disconnected” from the network, like models 1-6 + 8 and 9 in the attached image.
Is this an issue? Should I rather leave the A-matrix fully connected and then just test modulations of connections?
Any help much appreciated,
Haakon
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