thank you for your useful comments!
On 02/10/2011 06:05 PM, Darren Gitelman wrote:
> You can deal with this by setting up the DCM file from the command
> line. If you set up a simpler DCM using the GUI you will see what
> fields you need. The 8 region limitation is mostly due to the gui (and
I was not aware of this possibility and it is good to know. On the other hand, I
would like to stick to the "relevant model space" principle as much as possible,
whereby I am much more interested in network-network than in within-networks
dynamics. But as you are pointing out, it may not be possible to study such
modulations with DCM, at least in its current implementation.
> I'm not sure how you could use a non-linear DCM in this scenario. You
> can't really setup a small DCM network as an input, per se. The two
> "subnetworks" would just be connected into the larger 4 region network
> perhaps through a common area. This would be through an intrinsic
> connection. DCM only accepts as inputs the condition-type vectors that
> it extracts from an SPM.mat file. You would also need other actual
> inputs into each of the subnetworks in order to drive overall system
> activity. Non-linear DCM's can be used to modulate an intrinsic
> connection, so perhaps you are thinking of using the 3 region
> subnetworks to modulate an external input into the 4 region network?
> However, I don't think you can modulate an input as DCM is currently
> set up, and you would still need to drive the subnetworks in some way.
One possibility I was wondering about is whether it would be possible to
constrain the within-network interactions, by modelling each netwtork as a
single VOI, i.e. extracting one VOI for network 1 based on a mask including the
activations of areas A,B,C,D, one VOI for network 2 including areas E,F,G and
one VOI for network 3 including areas H,I,J, and then study modality-dependent
bilinear modulations between networks in a simple model including these three VOIs.
Does this make any sense? Or do such multi-regional VOIs violate the biophysical
assumptions or any other assumptions in DCM?
Thank you again,
Marco Tettamanti, Ph.D.
San Raffaele Scientific Institute
Via Olgettina 58
I-20132 Milano, Italy
Email: [log in to unmask]
SOSTIENI ANCHE TU LA RICERCA DEL SAN RAFFAELE.
NON C'E' CURA SENZA RICERCA.
Per donazioni: ccp 42437681 intestato a Fondazione Arete' Onlus del San Raffaele.
Per informazioni: tel. 02.2643.4461 - www.sanraffaele.org