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

[Makoto Miyakoshi]

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