[Eeglablist] Trouble with dipole locations using standard MNI channel locations: No co-registration produces dipoles that appear to be rotated 90 degrees.

[Arnaud Delorme]

Dear James and Makoto,

it is not a problem. We have been fighting with Makoto over that.
The BEM and the Spherical models use different coordinate systems, that's all (and they are rotated with respect to each other). EEGLAB can adapt to any model orientation and should detect most montage automatically and rotate them accordingly.
Thanks,

Arno

On Sep 10, 2012, at 8:11 PM, Makoto Miyakoshi wrote:

> Dear James,
> 
> You are right. This is a well-known 90 degree rotation problem.
> Please coregister your channels to the model, or manually rotate your
> montage to 90 degree to recover the original position.
> 
> Makoto
> 
> 2012/9/10 James Schaeffer <schaefj3 at gmail.com>:
>> Dear eeglablist,
>> 
>> I am source localizing with dipfit2 in eeglab 11.0.3.1b with a 128 biosemi
>> system and have renamed my channel labels to their closest match in the
>> 10-20 system. After re-naming, I loaded the standard MNI channel locations
>> through 'look up locs' under 'edit:channel locations' in the GUI so I could
>> use them in dipfit. I thought that if I did this, there would be no need for
>> me to co-register my channels with the dipfit head model (as the tutorial
>> suggests). However, if I do not co-register, (by selecting 'no coreg' in the
>> head model settings) my dipole locations appear to be rotated 90 degrees
>> clockwise (when viewed from above), relative to their scalp maps. If I do
>> co-register the standard MNI channel locations, and warp the montage, the
>> dipole locations appear where they are expected (I think). I tested this by
>> fitting dipoles to what I believe to be an eye artifact in a few datasets.
>> Without co-registration, the dipoles appeared in the right inferior temporal
>> lobe; with co-registration (and warping), the dipoles appeared in the left
>> eye (as I expected).
>> 
>> Has anyone else encountered this? Am I missing an important step when using
>> standard MNI locations without co-registration? Is co-registration and
>> warping required even when using the standard MNI locations? Any help would
>> be greatly appreciated.
>> 
>> Thanks in advance,
>> 
>> James
>> 
>> 
>> 
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> 
> 
> 
> -- 
> Makoto Miyakoshi
> JSPS Postdoctral Fellow for Research Abroad
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
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