[Eeglablist] dipole localizaton

[Arnaud Delorme]

Dear Jung,

the tranformation was done by coregistering the template MRI head with 
the sphere model as explained on this tutorial page

http://www.sccn.ucsd.edu/eeglab/dipfittut/dipfit.html#topoplot

The transformation is embeded in the function dipplot().
The new DIPFIT2 that will be released (very soon hopefully) has a 
function that convert spherical coordinates to closest MNI coordinates 
using the following homogenous tranformation matrix.

besa2SPM = [
   0.0101   -0.9400         0    0.5588
    1.1889    0.0080    0.0530  -18.0041
   -0.0005   -0.0000    1.1268    1.8045
         0         0         0    1.0000 ];

test_spherical_point = [10 10 10]; % sphere radius is 85 mn

transformed_mni_point = besa2SPM * [test_spherical_point 1]';
transformed_mni_point = transformed_mni_point(1:3)'

You may then transformed the MNI coordinates to talairach coordinates 
using other matlab scripts, for example:

http://www.mrc-cbu.cam.ac.uk/Imaging/Common/mnispace.shtml

containing the short function

function outpoint = aff_mni2tal(inpoint)
Tfrm = [0.88 0 0 -0.8;0 0.97 0 -3.32; 0 0.05 0.88 -0.44;0 0 0 1];
tmp = Tfrm * [inpoint 1]';
outpoint = tmp(1:3)';

or

http://godzilla.kennedykrieger.org/sw/mri_toolbox/mri_toolbox/mni2tal.html

Hope this helps,

Arno

Jung, Ki-Young wrote:

> Dear all
>
> I'd like to know which method used to do transposition of the dipoles 
> from the spherical head model to the standard MRI template in dipfit 
> function.
>
> Any references or comments will be welcome.
>
> Many thanks
>
>  
>
> Jung, Ki-Young
>

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