Dear Vladimir,
in some fMRI studies I've read that negative values in Ep.A represent
inhibitory effects while positive values represent excitatory
connections. Is this interpretation correct and is it similar in EEG?
As far is I understood all connections from one region to another
should be excitatory in the model since "it has been shown that
extrinsic cortico-cortical connections are exclusively excitatory"
(SPM book, p.418).
Thanks,
Nils
__________________
Dipl.-Math. Nils Rosjat
Universität zu Köln
Biozentrum
Zülpicher Straße 47b
50674 Köln
[log in to unmask]
Zitat von Vladimir Litvak <[log in to unmask]>:
> Dear Nils,
>
> See
>
> https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=SPM;ca3e9d95.0903
> https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=SPM;62842ebb.1107
> https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=SPM;32028f0c.1108
>
> Regarding your last question, the answer depends on whether you write your
> own equations or use SPM code such as spm_fx_erp. In SPM code the
> parameters are exponentiated (see around line 76) so the input you provide
> shouldn't be.
>
> Best,
>
> Vladimir
>
>
>
> On Thu, Jul 17, 2014 at 1:28 PM, Nils Rosjat <[log in to unmask]> wrote:
>
>> Dear SPM experts,
>>
>> I have a question concerning the DCM results for EEG (ERP). After
>> inverting the DCM you can review the coupling matrices A, B and C either in
>> the GUI as coupling(A), coupling(B) and coupling(C) or at the level of
>> MATLAB command lines in DCM.Ep.A, DCM.Ep.B and DCM.Ep.C. When you compare
>> these matrices they are not the same.
>>
>> My questions are:
>> 1.) What is the difference between the GUI and the command line matrices?
>> 2.) How do you get for example from coupling(A) to DCM.Ep.A?
>> 3.) Which one should be used for further analysis?
>> 4.) If I wanted to set up the equations for the neural mass model used in
>> DCM manually for numerical simulations which coupling strengths would I
>> use, the ones from the GUI or the ones accessed by the MATLAB command line?
>>
>> Thank you in advance,
>> Nils
>> __________________
>> Dipl.-Math. Nils Rosjat
>> University of Cologne
>> Biocenter
>> Zuelpicher Str. 47b
>> 50674 Cologne
>> [log in to unmask]
>>
>
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