Help with dipolesimulation

[Vladimir Litvak]

Dear Luis,

What Jan-Mathijs was saying is that you can use the dipolesimulation
function to project any arbitrary source waveform to the sensors.
There are some limited tools in the function to create such a waveform
on the fly (cfg.frequency) but a much more flexible way would be to
create the waveforms in your own script using Matlab tools and then
just use dipolesimulation to project them  (with cfg.dip.mom as JM
explained). Also since the summation of sources is linear, you can run
dipolesimulation several times with different inputs and then add the
resulting data. You can use freqsimulation function for generating
your source waveforms or use your own code.

Stanley is partially right that phase locking only makes sense for the
same frequency (although there might be more complex relations having
to do with phase across frequencies), but that's another issue.

Large part of Fieldtrip is about localizing oscillatory activity.
That's exactly what beamforming is for, particularly DICS.

Best,

Vladimir

On Sun, Apr 19, 2009 at 6:46 PM, Stanley Klein <sklein at berkeley.edu> wrote:
> Luis,
> Phase doesn't make much sense if frequencies are different.
> In your simulation are you doing stimulation with two frequencies (SSVEP)?
> If so then you can do the simulation with two dipoles each with two
> frequencies. If you aren't doing stimulation then I'd think you'd just want
> to choose one frequency (say with an octave banwidth) for doing your source
> localization.
>
> Does Fieldtrip have good tools for doing that sort of localization?
> Stan
>
> On Sun, Apr 19, 2009 at 10:22 AM, Luis Morán <lmoranr at gmail.com> wrote:
>>
>> But that doesn't solve my problem.  I've completed the simulation with 2
>> dipoles but using the same frequencies and phases. What I need is use a
>> different frequency in each dipole
>>
>> As I understand the dipolesimulation function at 'cfg.frequency' we can
>> specify only a value
>>
>> Any other advice?
>>
>> Thanks a lot in advance
>>
>>
>> 2009/4/19 jan-mathijs schoffelen <j.schoffelen at psy.gla.ac.uk>
>>>
>>> Dear Luis,
>>>
>>> I guess that the desired functionality is already there, the only thing
>>> which you have to do is specifying your input configuration meaningfully.
>>> The most relevant line is line 215, which states (more or less) trial =
>>> lf * dipmom * dipsignal;
>>>
>>> lf contains the leadfield (forward model) for the dipoles at the
>>> positions in cfg.dip.pos, and has dimensionality Nchan x (Ndipolex3), so it
>>> is a concatenation (in the columns) of the single position's leadfields.
>>> dipsignal is an NdipolexNtime matrix containing the dipoles' time series.
>>> For the matrix product to work, dipmom should be of dimensionaity
>>> (Ndipolex3)xNdipole (right?). This is the key to the solution to your
>>> problem:
>>>
>>> cfg.dip.mom should be something like  [orix1 0;oriy1 0; oriz1 0;0 orix2;0
>>> oriy2;0 oriz2], with ori(xyz)(1/2) specifying the moments of your dipoles.
>>>
>>> I hope this helps,
>>>
>>> Jan-Mathijs
>>>
>>>
>>> On Apr 18, 2009, at 12:20 PM, Luis Morán wrote:
>>>
>>>> Hi dear Fieldtrippers!!
>>>>
>>>> I'm trying to make a dipolesimulation with two dipoles. I need to use
>>>> different frequencies and phases for each dipole and I don't know very well
>>>> how to modify the dipolesimulation function.
>>>>
>>>> Any advice?
>>>>
>>>> Thanks in advance
>>>>
>>>> Best regards
>>>> --
>>>> Luis Morán Rodríguez
>>>>
>>>> Bioengineering Group
>>>> Universidad Politecnica Madrid
>>>> ----------------------------------
>>>>
>>>> The aim of this list is to facilitate the discussion between users of
>>>> the FieldTrip toolbox, to share experiences and to discuss new ideas for MEG
>>>> and EEG analysis.
>>>>
>>>> http://listserv.surfnet.nl/archives/fieldtrip.html
>>>>
>>>> http://www.ru.nl/fcdonders/fieldtrip/
>>>>
>>>
>>> ----------------------------------
>>> The aim of this list is to facilitate the discussion between users of the
>>> FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG
>>> and EEG analysis. See also
>>> http://listserv.surfnet.nl/archives/fieldtrip.html and
>>> http://www.ru.nl/neuroimaging/fieldtrip.
>>
>>
>>
>> --
>> Luis Morán Rodríguez
>>
>> Altentic
>>
>> lmoran at altentic.com
>>
>> ----------------------------------
>>
>> The aim of this list is to facilitate the discussion between users of the
>> FieldTrip toolbox, to share experiences and to discuss new ideas for MEG and
>> EEG analysis.
>>
>> http://listserv.surfnet.nl/archives/fieldtrip.html
>>
>> http://www.ru.nl/fcdonders/fieldtrip/
>
> ----------------------------------
>
> The aim of this list is to facilitate the discussion between users of the
> FieldTrip toolbox, to share experiences and to discuss new ideas for MEG and
> EEG analysis.
>
> http://listserv.surfnet.nl/archives/fieldtrip.html
>
> http://www.ru.nl/fcdonders/fieldtrip/

----------------------------------
The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/neuroimaging/fieldtrip.