[Mne_analysis] Estimates using mne_volume_source_space

Matti Hamalainen msh at nmr.mgh.harvard.edu
Fri May 22 22:02:17 EDT 2009
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Hi Andrés,

On May 22, 2009, at 6:14 PM, Andres Felipe Salazar Gomez wrote:

> Hi MNE users,
>
> I have used the mne_volume_source_space command to get a source  
> space of 6
> dipoles. After getting my estimates I get a total of 18 sources
> orientations. I would like to know which sources correspond to what
> dipoles.
>
> If I have 18 sources, are they arrange so that the first 3 elements  
> are
> for the first dipole, the second third for the second dipole and so  
> on?
>
> I think it is so but I want to confirm it.
>
> Thank you very much for your comments and suggestions.

The data are arranged exactly as you describe. The forward matrix A =  
(a_1 a_2 a_3 .... a_3N) where N is the number of sources and column  
a_1 is the the field of the dipole oriented in the x direction at  
location 1, a_2 is the field of the dipole oriented in the y direction  
at location 1, a_3 is the field of the dipole oriented in the z  
direction etc.

If the --mricoord option was specified when the forward solution was  
computed, the x, y, and z axes are those of the MRI (RAS) coordinate  
system. In the absense of this option, the orientations are defined by  
the MEG head coordinate system.

I hope this helps

- Matti


---------

Matti Hamalainen, Ph.D.
Athinoula A. Martinos Center for Biomedical Imaging
Massachusetts General Hospital

msh at nmr.mgh.harvard.edu






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