[FieldTrip] Generate a source model where dipoles are perpendicular to the cortex surface

[Eelke Spaak]

Hi Ying,

In addition to this, of course first you would need a model of the
cortical surface for your subjects. See
http://fieldtrip.fcdonders.nl/tutorial/minimumnormestimate for how to
obtain such a model (using FreeSurfer) and getting it into FieldTrip.

Best,
Eelke

On 22 May 2014 10:56, "Jörn M. Horschig" <jm.horschig at donders.ru.nl> wrote:
> Hi Ying,
>
> when computing the leadfields you can set the option cfg.reducerank, which
> 'nulls' the dimension(s) which explain(s) the least variance (this is not
> quite true, but figuratively speaking). I think this is what comes closest
> to what you are looking for. There is no way to explicitly set desired
> orientations to zero apart from modifying the leadfield structure yourself.
> But that should be easily achievable, right?
>
> Best,
> Jörn
>
>
> On 5/22/2014 10:26 AM, Ying Li wrote:
>>
>> Dear all,
>>
>> I tried to use fieldtrip to generate a source space and calculate lead
>> field matrix. I found that the dipoles in the source space has x, y, z
>> orientations. Is it possible to generate a source model where the dipole is
>> perpendicular to the cortex surface?
>>
>> Actually this can be very helpful, since it will reduce the unknown
>> variables and make the inverse problem easier to solve. Also, there are some
>> inverse algorithms which require the dipole to be perpendicular to the
>> cortex surface.
>>
>> Thanks a lot!!!
>>
>> Best,
>>
>> Ying
>>
>>
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>
>
>
> --
> Jörn M. Horschig
> PhD Student
> Donders Institute for Brain, Cognition and Behaviour
> Centre for Cognitive Neuroimaging
> Radboud University Nijmegen
> Neuronal Oscillations Group
> FieldTrip Development Team
>
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