apologies, the original posting wasnt included:
Hi, Ive begun exploring using the PEB framework for DCM of fMRI and have a few questions I hoping can be clarified..
1. I have a patient sample and a control sample that Id like to compare. Is it appropriate/valid to perform the first-level model estimations using the Full+BMR PEB option on the two groups separately (ie one GCM per group), and then concatenate these two estimated GCMs for the second-level PEB analysis (which includes the 1 -1 group regressor)?
2. Is it possible/meaningful to compare the fitness of PEB models? That is, I have a single full DCM model per subject that I search using PEB to prune connections, and would be interested to make the determination for example that a PEB model which includes age as a regressor fits better/worse than a PEB model without age included? On this note, is the PEB-resulting BMA.F an indicator of the model evidence of the reduced model, and thus if exp(BMA.F) is 0 then the BMA model may not be fitting/explaining the data very well?
3. Is it possible to recover subject-level parameters following the second-level PEB search? For example, if I see a strong evidence of a group difference for a particular connection, and wanted look at the group-averages, where would I find the Hz values for each subject (the BMA only appears to be storing sample means, unless Im missing where they are stored)?
Many thanks,
GS
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