[FieldTrip] A problem

[Robert Oostenveld]

Dear Ayda

On 19 Jan 2012, at 20:01, aida ghahremani wrote:
> I have the coordinates of the cortex. Would you please help me to locates the sources (dipoles) which best explain the EEG?

You can pass the cortical sheet to the ft_sourceanalysis function (or to the ft_prepare_leadfield function) to use all vertices of the cortical sheet as dipole locations. This is also the approach used in http://fieldtrip.fcdonders.nl/tutorial/minimumnormestimate#source_model. The vertex positions should be specified as cfg.grid.pos.

> How I can make their orientations normal to the cortex?

You'll have to determine the dipole orientation at each vertex outside of fieldtrip, but you can use the fieldtrip/forward/private/normals.m to help you with it. If you specify the dipole orientations as cfg.grid.mom, then the leadfield will computed for a dipole in that direction. See line 227 in ft_prepare_leadfield.

best
Robert