[Eeglablist] importing channel locations from NDI Krios

[Clement Lee]

Hi Sofia,

Looks like I accidentally dropped the EEGLAB list in my last reply, so let
me add everyone back.

Good thing you have the fiducials recorded! I suggest processing them using
the same methods you applied to your other electrodes. After all is said
and done, you should check your fiducials to see if their locations are as
expected (on the correct plane or axis). The expectation is coordinate
system dependent, sometimes the nasion is (+X,0,0), sometimes the left ear
is +X, but sometimes the ears are only approximately on the axis,
etc. Check what coordinate system the NDI Krios uses. The FieldTrip wiki
page here might be useful:
https://urldefense.com/v3/__http://www.fieldtriptoolbox.org/faq/how_are_the_different_head_and_mri_coordinate_systems_defined/__;!!Mih3wA!UvbuEPuVYnXV6sclakBYqpnQUy5vREmnbZliBLks3CyjvqLYVFiaZTslRfX12FmWrwDnog$ 
).

Best,
Clement Lee
Applications Programmer
Swartz Center for Computational Neuroscience
Institute for Neural Computation, UC San Diego
858-822-7535


On Wed, Sep 2, 2020 at 2:39 AM Sofia Moraresku <sofi.moraresku at gmail.com>
wrote:

> Dear Clement,
> thank you for your reply. There was the native digitizer program (I'm not
> sure it was CURRY 8) on the computer which was used for the EEG experiment,
> but now for a while, I don't have access to it. As I remember,
> during digitizing the electrodes, the 3-D plot looked normal without
> rotation. Apart from electrode positions, I also have the coordinates of
> the fiducial locations (x,y,z) in the final csv file. Is it possible
> somehow to use these fiducial locations in EEGLAB to adjust electrode
> positions?
> Thank you.
>
> Best,
> Sofia
>
> пн, 31 авг. 2020 г. в 19:55, Clement Lee <cll008 at eng.ucsd.edu>:
>
>> Hi Sofia,
>>
>> I have not used the NDI Krios before, but have a suggestion. It sounds to
>> me that your importing methods are correct and that the axial rotations are
>> not because of your methods; afterall, you should only have rotations in 90
>> degree increments. It's possible that the fiducial locations (nasion,
>> left&right preauricular) have been recorded inaccurately when you first
>> digitized the electrodes. Do you have the native digitizer program that
>> comes with the NDI Krios (is it CURRY 8?). Does the 3-D plot there show the
>> 'correct' orientation or does it also seem rotated?
>>
>> Best,
>> Clement Lee
>> Applications Programmer
>> Swartz Center for Computational Neuroscience
>> Institute for Neural Computation, UC San Diego
>> 858-822-7535
>>
>>
>> On Mon, Aug 31, 2020 at 10:41 AM Sofia Moraresku <
>> sofi.moraresku at gmail.com> wrote:
>>
>>> Hello,
>>>
>>> Has anybody imported channel locations file from NDI Krios (Compumedics
>>> NeuroScan)? As this format is not supported by EEGLAB, I tried to do it
>>> manually using Matlab .xyz format for importing and changing slightly txt
>>> file such as X = -Y, Y = X, Z = Z. After importing to EEGLAB, I
>>> also optimized the head center. However, on the 3D plot, it still seems
>>> that all channels are located on the wrong positions, probably turned to
>>> some angle on all axes. I do not know how to figure out the exact
>>> angle. Could somebody advise on how to adjust channel locations or maybe
>>> recommend another way of importing this file format?
>>> Thank you in advance.
>>>
>>> Best regards,
>>> Sofia
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>>