Dear SPM Developers / Users!
I estimated a model of the Attention to Motion dataset (model: 3 nodes, 3 external inputs, deterministic, one-state, bilinear DCM) to try out the post hoc optimization method for DCM. Is it possible to get invalid models out of the optimization results? And although the results seem mathematically correct, how can a model like in my example be interpreted?
I attached my example as an image. Here I estimated a full model of this network (A), and the results are the parameter estimates in (B). I tried to optimize this model with post hoc optimization option in DCM, and got the results in (C). Some connections in the A matrix are zeroed out (or resetted to prior values) like A(3:1), while some inputs still modulate this connection. Can I consider the optimized model invalid, as it seems like that some connections which are modulated should not be present? Or can models like this be interpreted somehow?
Best regards,
Csaba Aranyi
|