Dear Martin,
To my knowledge there are a number of papers on your last topic.
Synthetic data with different neural parameters (connectivity structures):
W.D. Penny, K.E. Stephan, A. Mechelli, and K.J. Friston. Comparing Dynamic Causal Models. NeuroImage, 22(3):1157-1172, 2004.
W. Penny (2011). Comparing Dynamic Causal Models using AIC, BIC and Free Energy. Neuroimage. Available online 27 July 2011.
Synthetic data with different hemodynamic models:
K.E. Stephan, N. Weiskopf, P.M. Drysdale, P.A. Robinson, and K.J. Friston. Comparing hemodynamic models with DCM. NeuroImage, 38:387-401, 2007
Best, Will
> -----Original Message-----
> From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]]
> On Behalf Of Martin Pyka
> Sent: 02 May 2012 12:41
> To: [log in to unmask]
> Subject: Re: [SPM] DCM fails to select model that generated the data
>
> > That makes sense that my problem might have something to do with the
> EM algorithm settling on a relatively poor local maximum for the
> correct model. How can one mitigate this risk? If the EM algorithm
> starts at an arbitrary point, then it would seem that increasing
> subject or run number would help. Are there properties of a specific
> model structure (or space) that would make one more or less susceptible
> to this?
>
> This is a good question. I don't know how important this problem in DCM
> actually is and (if it is important) how to avoid it. Maybe, there is
> already an article about it that I am not aware of.
>
> If you have more detailed pre-assumptions about the real neural and
> hemodynamic paramaters of your model it could help to start the EM with
> those values. If this is not possible, it can help to run the EM a few
> times with different starting positions.
>
> In general, I think, it is necessary to test if model selection works
> properly using synthetic data generated with various (!) neural and
> hemodynamic parameters. I would like to know if this has been done
> before.
>
> Best,
> Martin
>
>
>
> --
> SPM for programmers
> http://spm.martinpyka.de
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