[Eeglablist] Issue with 3D Plotting

Makoto Miyakoshi mmiyakoshi at ucsd.edu
Fri Jul 12 20:52:07 PDT 2019


Dear Mariya,

> 1. Do you know why this rotation is occurring?

Three are two or three coordinate conventions, and they define X and Y
oppositely. This is why the coregistration process is important, it is
confirming which side is right and which side is left.

> 2. Can you please be more specific about how to enter -pi/2 to Yaw into
the co-registration? Would this correct the .ced file?

-pi/2 means 90 degrees to the right. It means 'Rotate the channels to the
right for 90 degrees'. The input uses radian, and 90 degrees is pi/2
(because pi radian is 180 degrees).

I would say you don't need to worry about these things as long as your
channels are correctly aligned to the head. Once you confirm the right
alignment, you can almost safely forget what they are. However, if you see
frontal dipoles in the right temporal area, you should remember this and
suspect if you screwed up the coregistration process.

Good luck!

Makoto

On Fri, Jul 12, 2019 at 1:58 PM Mariya Chernenok <mchernenok at ucdavis.edu>
wrote:

> Hi Makoto,
>
> Thank you for your reply! I just have a couple of follow up questions:
> 1. Do you know why this rotation is occurring?
> 2. Can you please be more specific about how to enter -pi/2 to Yaw into
> the co-registration? Would this correct the .ced file?
>
> Thank you so much!
>
> Best,
> Mariya
>
> On Thu, Jul 11, 2019 at 3:24 PM Makoto Miyakoshi <mmiyakoshi at ucsd.edu>
> wrote:
>
>> Dear Mariya,
>>
>> Most likely, your channel config is 90 degrees rotated against the head
>> model for coregistration.
>> My initial guess is that you enter -pi/2 to Yaw and it'll fix the problem.
>>
>> Makoto
>>
>> On Wed, Jul 3, 2019 at 12:57 AM Mariya Chernenok <mchernenok at ucdavis.edu>
>> wrote:
>>
>>> Hello,
>>>
>>> We are collecting ERP data using a 64 channel BrainCap collected with
>>> Neuroscan and are having issues with the 3D plots in EEGlab. All
>>> screenshots and files can be found here:
>>> https://drive.google.com/drive/folders/1KI5lpa94FllxEY6uKyCWSVsAhVbMYhvj
>>>
>>> When we plot the channel locations in 2D, it appears normal
>>> (see 2Dcoordinates_chanloc). And when we plot the 3D coordinates, it also
>>> appears normal (see 3Dcoordinates_chanloc).
>>>
>>> However, when we try to plot the channel locations in 3D, they appear to
>>> not be properly positioned on the head
>>> (see 3Dcoordinates_chanloc_2_back; 3Dcoordinates_chanloc_2). It looks as
>>> though the channels at the back of the head are shifted to the side.
>>>
>>> Once we add a spline file (included in link), this issue appears to be
>>> resolved (see 3Dcoordinates_chanloc_2000ms).
>>>
>>> I am also including the .ced file with our channel location coordinates
>>> and
>>> cap montage. We are wondering why our channel locations look distorted
>>> without the spline file and what is causing this problem? Adding in a
>>> spline file to re-assign channel locations appears to resolve this issue,
>>> however, how do we verify that our channel locations are in the correct
>>> location?
>>>
>>>
>>> Please let me know if you need any additional information!
>>>
>>> Best,
>>> Mariya
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>>
>>
>> --
>> Makoto Miyakoshi
>> Assistant Project Scientist, Swartz Center for Computational Neuroscience
>> Institute for Neural Computation, University of California San Diego
>>
>
>
> --
> Mariya Chernenok, M.S.
> PhD Student
> Human Development Graduate Group
> Neurocognitive Development Lab
> University of California, Davis
>


-- 
Makoto Miyakoshi
Assistant Project Scientist, Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego


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