Dear Haoran,
You should include all sources in all models but if you don't connect
them you don't have to draw them in your diagrams. That's probably
what happened in that paper. Your BMS is only valid if data identity
verification does not give an error.
Best,
Vladimir
2011/7/19 飞鸟 <[log in to unmask]>:
> Dear Vladimir,
> Thank you for your advice! It didn't work when I set the 'verify data
> identity' to 'yes'. However, in this paper(Dynamic causal modeling of
> subcortical connectivity of language), the author did BMS, though each
> family didn't include all sources. Then as you said, its BMS would be
> invalid?
> Best regards.
> Haoran.
>
> At 2011-07-18 17:28:07，"Vladimir Litvak" <[log in to unmask]> wrote:
>
>>Dear Haoran,
>>
>>When you are doing your model selections, there is an option 'Verify
>>data identity'. It's false by default. Set it to 'yes'. You might then
>>get some error messages when you run BMS. That would mean that you
>>model comparison was not valid. What you should do is include both
>>Amygdala and the hidden source at [300 300 300] in all your models and
>>connect either one or the other. So you models should only differ in
>>the connectivity section and all the rest should be the same. Also
>>make sure that you use the ECD option (and not IMG) and your SPM is up
>>to date. If you do everything correctly then I would expect that if
>>two families only differ in whether the disconnected source is hidden
>>or not they should get exactly the same model evidence.
>>
>>Best,
>>
>>Vladimir
>>
>>2011/7/17 飞鸟 <[log in to unmask]>:
>>> Dear Vladimir,
>>> The difference between family A and C was the disconnected source's
>>> coordinate. For family A, the hidden source's coordinate was [300 300 300],
>>> for family C, the amygdala's coordinate was [-24 -8 -16].
>>> Haoran.
>>>
>>>
>>> At 2011-07-17 04:05:19，"Vladimir Litvak" <[log in to unmask]> wrote:
>>>
>>> Dear Haoran,
>>> So what was the difference in the disconnected source between family A and
>>> family C? On your scheme it was present in both cases, but only for C you
>>> call it 'Amygdala'. What was the difference?
>>> Vladimir
>>>
>>>
>>>
>>> On 16 Jul 2011, at 16:05, "飞鸟" <[log in to unmask]> wrote:
>>>
>>> Dear Vladimir,
>>> There's an error in the last letter. The detailed models in family A and
>>> family C were not absolutely same. However, this made few effects on the
>>> final BMS results(RFX). I meant that family A was always much better than
>>> family C.
>>> Considering the reliability, I did BMS (both RFX and FFX) again. This
>>> time Family A and family C, family B and family D had the same models in
>>> details.
>>> Family A included three models: A1(modulation on backward connection
>>> from DLPFC to ACC ), A2 (modulation on forward connection from ACC to DLPFC
>>> ), A3 ( modulation on both backward and forward connection between DLPFC and
>>> ACC). Family C was the same with family A except for the disconnected
>>> source.
>>> Return to my former question: if disconnected source doesn't affect
>>> the model, and if family A and family C have the same models except for the
>>> disconnected source. In this case, I think family A and family C will get
>>> similar performances. However, family A turned out to be much better than
>>> family C. It was this that confused me much. How do you think about this
>>> question?
>>> May you a happy weekend!
>>>
>>> Haoran.
>>>
>>> At 2011-07-15 20:22:14，"Vladimir Litvak" <[log in to unmask]> wrote:
>>>
>>>>Dear Haoran,
>>>>
>>>>From your schemes it's not clear what is the difference between A and
>>>>C or between B and D. Also it's not clear how the models within each
>>>>family differed so one thing you need to make sure is that you did
>>>>your comparisons correctly. However, assuming the result is valid I
>>>>would definitely interpret it with your interpretation (2). Namely,
>>>>there is no evidence for the necessity of the hidden source to explain
>>>>the data. Disconnected hidden source does not affect the model so your
>>>>model A could as well be without the hidden source at all (but you
>>>>were right to include the source without connecting it).
>>>>
>>>>Vladimir
>>>>
>>>>
>>>>
>>>>2011/7/15 飞鸟 <[log in to unmask]>:
>>>>> Dear SPM's users,
>>>>> I got some results using dynamic causal modeling (DCM for ERP,MEG).
>>>>> However, I was surprised at the results. I built four basic families of DCM
>>>>> (see attachment DCM_Model.jpg), expected the best model would appear in
>>>>> family B or D. To my surprise, family A turned out to be the best (see
>>>>> attachment bms_family). Then I inferred:
>>>>> 1. The hidden source might latently present several other subcortical
>>>>> sources which might closely related to my experiment. Moreover, family A had
>>>>> the least limitations of the connections between hidden source and other
>>>>> non-hidden sources. Finally, it became the best family of the four.
>>>>> 2. Family A was had much less connections relative to Family B and D, so
>>>>> its model complexity was lower. Finally, it became the best family of the
>>>>> four.
>>>>> Are the inferences above reasonable? Or what's the role of the hidden
>>>>> source when it has no connections between other sources in DCM? Any of your
>>>>> help will be greatly appreciated.
>>>>> Thank you!
>>>>>
>>>>> --
>>>>> Haoran LI (MS)
>>>>> Brain Imaging Lab,
>>>>> Research Center for Learning Science,
>>>>> Southeast University
>>>>> 2 Si Pai Lou , Nanjing, 210096, P.R.China
>
>
>
>
|
