[Eeglablist] Questions on function dipplot() and DIPFIT

[Arnaud Delorme]

Dear Young,

>    Question 1: DIPFIT uses function dipplot() provided by eeglab itself to plot dipoles in a 3D view. And dipplot() has draw a Ellipsoid coordinates to approximate the Talariach coordinates. The question is which Talariach axis is each ellipsoid axis corresponds to.

The elipsoid in Dipfit corresponds to the coregistration of the MNI
brain with standard EEG markers. For more details on the coregistration
see end of section A3.5 in
http://www.sccn.ucsd.edu/eeglab/dipfittut/dipfit.html

>    Question 2: How can I get a dipole Talariach Coordinates in eeglab?

You have to retreive the MNI coordinates of the dipoles from dipplot
(editing of code is required to return these coordinates). Then you have
to convert these coordinates to Tailairach (for instance use the
function http://eeg.sourceforge.net/mridoc/mri_toolbox/mni2tal_matrix.html).

>    Question 3: Further on question 1. What is the transformation between the four-sphere head model (eeglab default settings) and the MNI coordinates?

This is performed within Dipfit (line 549). In the future, we will allow
users to perform EEG/MRI coregistration and use homogenous matrix
transformation in dipplot (this is already possible if you use the
'coreg' option of dipplot; for beta use only).

Arno