Also note that you must use the ECD option for that. It won't work with IMG.
Vladimir
On Tue, Jun 14, 2011 at 4:11 PM, Vladimir Litvak
<[log in to unmask]> wrote:
> Dear Haoran,
>
> 2011/6/14 飞鸟 <[log in to unmask]>:
>> Dear Vladimir,
>> With regard to hidden source, I still have several simple questions. In
>> the paper(David O, etc. 2011) you recommended to me the last time, David
>> specify the hidden source's coordinate as [0 0 0]. However, you suggest that
>> we can specify the position further that 200mm from
>> the origin (like [300 300 300]). Are there any differences between [0 0 0]
>> and [300 300 300]?
>
> That research was done with older SPM. The [0 0 0] trick works only
> with single sphere model for MEG, but setting coordinates to a large
> number works for any head model and the effect is the same.
>
>> I don't know whether this is ture or not: as for any subcortical
>> regions, if I want to specify them as hidden sources, I just need to plus
>> 200mm to their coordinates respectively(e.g. Cingulate [0 36 28] , change to
>> [200 236 228] )?
>
> You just need to set the coordinates to a large number, like [300 300
> 300]. There is no need to use different coordinates for different
> sources, the effect will be the same.
>
>> Further, could I specify two or more hidden sources in my model? If so,
>> how can I specify the coordinates for them? Set both of them to [0 0 0] or
>> others?
>
> You can use [300 300 300] for all your hidden sources. You can have
> more than one but remember that you must also have non-hidden sources
> with some meaningful connectivity to the hidden sources. Otherwise you
> won't be able to get something meaningful from the model. I'd also not
> exaggerate with the hidden source. 5 non-hidden, 1 hidden is OK, but 5
> hidden 1 non-hidden is unlikely to work.
>
> Best,
>
> Vladimir
>
>> Thank you!
>> Best wishes to you!
>>
>> Haoran.
>>
>> At 2011-06-11 00:56:11,"Vladimir Litvak" <[log in to unmask]> wrote:
>>
>>>Dear Haoran,
>>>
>>>There are two answers to that. The first answer is that whether there
>>>is any signal in the MEG from amygdala or hippocampus is subject to
>>>debate and there is some evidence in favor of that but it's not
>>>conclusive. The second answer is that you can include sources in your
>>>DCM model even if there is no signal in the MEG/EEG from these sources
>>>and learn something about those 'hidden' source from their
>>>interactions with sources that are observed. As an example you can
>>>look at http://www.ncbi.nlm.nih.gov/pubmed/21325540 . You can either
>>>just place sources e.g. in the hippocampus the usual way or (in an
>>>up-to-date SPM) if you specify the position further that 200mm from
>>>the origin (like [300 300 300]) the lead field of the source will be
>>>set to zero and then it will be truly hidden source. You can compare
>>>the two ways with model comparison to see if there is really any
>>>evidence for the source being at particular location or not.
>>>
>>>Best,
>>>
>>>Vladimir
>>>
>>>2011/6/9 飞鸟 <[log in to unmask]>:
>>>> Dear spm's users,
>>>> Thanks for your concern! As DCM for EEG/MEG is based on nerual mass model,
>>>> I wonder that can I apply DCM for EEG/MEG to cerebral limbic system( such as
>>>> cingulate, hippocampus and amygdala etc). In other words, is it valid to
>>>> specify my model not only include cortex regions(e.g. frontal lobe, temporal
>>>> lobe etc.), but also include cingulate or other limbic system's regions?
>>>> Any help will be appreciated!
>>>>
>>>> --
>>>> Haoran LI (MS)
>>>> Brain Imaging Lab,
>>>> Research Center for Learning Science,
>>>> Southeast University
>>>> 2 Si Pai Lou , Nanjing, 210096, P.R.China
>>>>
>>>>
>>
>>
>>
>> --
>> Haoran LI (MS)
>> Brain Imaging Lab,
>> Research Center for Learning Science,
>> Southeast University
>> 2 Si Pai Lou , Nanjing, 210096, P.R.China
>>
>>
>
|