Dear Carlo,

You should look at the posteriors in DCM.Ep rather than at the priors.
In any case a more meaningful way to look at the results would be to
export the connectivity matrices to images.

Best,

Vladimir


On Mon, Aug 20, 2012 at 2:29 PM, Huber, Carlo A <[log in to unmask]> wrote:
> Dear Vladimir,
>
>
>
> Indeed the model captures the data very well, so I may keep it.
>
> DCM.M.pE. is the place to look for the Matrices, right?
>
> If I subtract the values of the A-Matrix from the B-Matrix than I have
>
> all zeros which corresponds to having not a "real" B-Matrix.
>
> Thank you for the reply,
>
> Best,
>
> Carlo
>
>
>
>
> Vladimir Litvak <[log in to unmask]> hat am 20. August 2012 um 15:12
> geschrieben:
>
>> Dear Carlo,
>>
>> If you have only one condition there should be no B matrix or it
>> should be all zeros. If you have the same A and B I could only explain
>> it if they are both all zeros and that would indicate failure of fit.
>> I suggest that you examine the model fit (time modes and
>> time-frequency) and see if the model captures any of your data
>> features before trying to interpret the connectivity matrices.
>>
>> Best,
>>
>> Vladimir
>>
>> On Mon, Aug 20, 2012 at 1:59 PM, Huber, Carlo A <[log in to unmask]>
>> wrote:
>> > Dear Vladimir,
>> >
>> >
>> >
>> > Thank you for your answers. Did I unterstand correctly that having only
>> > one
>> > condition in the DCM (e.g. slow finger movement) than the A-and B-Matrix
>> > have exactly the same values. Or is it something wrong with the data or
>> > the
>> > model that I get the same results for A and B-Matrix.
>> >
>> > Thank you for consideration,
>> >
>> > Best,
>> >
>> > Carlo
>> >
>> >
>> > Vladimir Litvak <[log in to unmask]> hat am 18. August 2012 um
>> > 15:22
>> > geschrieben:
>> >
>> >> Dear Carlo,
>> >>
>> >> On Fri, Aug 17, 2012 at 11:16 AM, Carlo Huber <[log in to unmask]>
>> >> wrote:
>> >> > Hej, Hej,
>> >> >
>> >> > I am working on a simple motor task and am trying to model
>> >> > connectivity
>> >> > patterns in core motor regions.
>> >> > Concerning DCM for induced responses, I have two basic questions and
>> >> > am
>> >> > happy for any consideration.
>> >> > .
>> >> > First, you have the option for several inputs when you define your
>> >> > model. I am considering a time window of 1000ms and
>> >> > the induced activity linked to movement starts around 150-250 ms
>> >> > (with
>> >> > trial-to-trial variability). I am thinking now if I may use
>> >> > several inputs, e.g. 100 200 300 400 500ms because 1. of the
>> >> > variability
>> >> > of the onset 2. the induced components are not nearly as sharp
>> >> > as an averaged ERP and 3. the movement needs to bei maintained
>> >> > steadily
>> >> > consciously which I interpret as ongoing input which I want to put
>> >> > into the
>> >> > model;
>> >>
>> >> You could also consider changing the width of the input pulse. This is
>> >> an option available in the latest SPM8 update. You could for instance
>> >> have one input in the middle of your hold period with sd wide enough
>> >> so that there will be some input throughout that period + maybe
>> >> something for the onset, you can play with it and do model comparisons
>> >> to find the optimal input configuration. I think it's preferable to
>> >> multiple discrete inputs which will generate 'bumps' that the model
>> >> will have to try to suppress by dynamics.
>> >>
>> >> > I don´t have any results with just one input, which might be due to
>> >> > the
>> >> > prior for the A-Matrix (see DCM.M.pE.A), so that the modell reaches
>> >> > very
>> >> > early convergence?? The other thing that prevented too fast
>> >> > convergence was
>> >> > changing the scaling factor in the spm_cond_units.m script (e.g. to
>> >> > fixed
>> >> > number of 1000) though I am not completely aware of the effect of
>> >> > this.
>> >> > .
>> >>
>> >> This just scales the data. I would try changing the inputs with the
>> >> scaling as it was. All those things have been optimized to work
>> >> together by Karl mostly by trial an error so by changing some random
>> >> bit in the code it's much easier to break it than to fix it.
>> >>
>> >> > My second question: When I am only analyzing one condition, the
>> >> > values
>> >> > for the A- and B-Matrix are the same. Is it therefore advisable in
>> >> > general
>> >> > to use a second, contrasting condition (e.g. rest). I think that I
>> >> > should
>> >> > not use a similiar condition (e.g. fast and slow finger movement). In
>> >> > general, when I am sure about the sources I am using in the modell
>> >> > and that
>> >> > these are engaged in the task, is it even better to use only one
>> >> > condition
>> >> > without the contrast to a control condition.
>> >> > .
>> >>
>> >> In general it is more interesting to look at the condition effects (B
>> >> matrix) as they are more likely to reveal something interesting.
>> >> However, I don't think having rest as the second condition is a good
>> >> idea as rest doesn't have any interesting dynamics to model so for
>> >> DCM-IR the best thing to do is just to leave the coupling at zero
>> >> which is not very interesting. Fast and slow finger movements are more
>> >> interesting to compare, the only issue is how to keep the timing in
>> >> the trial comparable. In general there are many things you can do, but
>> >> only a small subset of them is likely to yield interpretable  results
>> >> and that's what I'd suggest you to focus on.
>> >>
>> >> Best,
>> >>
>> >> Vladimir
>> >>
>> >> > Dear all, thank you very much for reply. All considerations are
>> >> > welcome.
>> >> > Carlo
>> >> >
>> >> > (Carlo Huber, University Hospital Cologne, Neurology, Germany)
>> >> >
>> >
>> > Carlo A Huber
>> > Assistenzarzt Neurologie
>> > Wissenschaftlicher Mitarbeiter
>> > AG Bewegungsstörungen und Tiefe Hirnstimulation
>> > Klinische Forschergruppe 219 (DFG)
>> > Klinik und Poliklinik für Neurologie
>> > Universitätsklinikum Köln
>> > Kerpener Str. 62
>> > 50924 Köln
>> > Germany
>> >
>> > Tel: +49-(0)221-478-97602
>> > Fax: +49-(0)221-478-97819
>> > email: [log in to unmask]
>> >
>> >
>> > http://neurologie-psychiatrie.uk-koeln.de/neurologie/forschung/ag-bewegungsstoerungen-tiefe-hirnstimulation
>> >
>> > The contents of this email and any attachments are confidential. They
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>
> Carlo A Huber
> Assistenzarzt Neurologie
> Wissenschaftlicher Mitarbeiter
> AG Bewegungsstörungen und Tiefe Hirnstimulation
> Klinische Forschergruppe 219 (DFG)
> Klinik und Poliklinik für Neurologie
> Universitätsklinikum Köln
> Kerpener Str. 62
> 50924 Köln
> Germany
>
> Tel: +49-(0)221-478-97602
> Fax: +49-(0)221-478-97819
> email: [log in to unmask]
>
> http://neurologie-psychiatrie.uk-koeln.de/neurologie/forschung/ag-bewegungsstoerungen-tiefe-hirnstimulation
>
> The contents of this email and any attachments are confidential. They are
> intended for the named recipient(s) only. If you have received this email in
> error please notify the system manager or the sender immediately and do not
> disclose the contents to anyone or make copies.