Conversion from MNI/Talairach to 10-10 EEG

Discussions
1

Hello everybody,

I’ve seen a similar discussion on how to convert standard 10-10 EEG coordinate into the MNI space, but I could not figure out how to do the opposite: converting MNI or Talairach coordinates into the closest EEG position.

In the past there was the Münster T2T converter that did that, but that’s not available anymore. I was wondering whether BrainStorm does that as well.

Thank you
Giuseppe

2

Hi Giuseppe,

You can use the function cs_convert to get the MNI coordinates in “Brainstorm coordinates”:
http://neuroimage.usc.edu/brainstorm/CoordinateSystems#Converting_between_coordinate_systems
P_scs = cs_convert(sMri, ‘mni’, ‘scs’, P_mni); % MNI coordinates => SCS

Then look for the close electrode:
[minDist, iClosest] = min(sum(bsxfun(@minus, [ChannelMat.Channel.Loc], P_scs’) .^ 2, 1));

Cheers,
Francois

3

Hi Francois,

thank you for the suggestion.

I’m afraid I could not make it work. I used the ICBM 152 and I successfully obtained P_scs.
But when I run
[minDist, iClosest] = min(sum(bsxfun(@minus, [ChannelMat.Channel.Loc], P_scs’) .^ 2, 1));

I do not understand what I need to use as [ChannelMat.Channel.Loc]?

What I would like to have as output is something like “the position corresponds to midway between P4 and P6”. I don’t know if I was clear.

Thank you again
Giuseppe

4

Hello Giuseppe!

The conversion of the MNI coordinates to scalp sites is a significant challenge. Recently, we have developed a probabilistic mapping from any cortical MNI coordinates to a standardized scalp (CPC) system. Based on the properties of the CPC system, it is possible to quickly and accurately place tDCS electrodes or TMS coils. Our work has been published in the journal Brain Stimulation (doi.org/10.1016/j.brs.2023.11.011), and we have also developed a free online tool for querying any cortical MNI coordinates to the optimal scalp site (transcranial-brain-atlas.org/MNI2CPC). We warmly welcome everyone to use our method. If you have any questions, please do not hesitate to contact me.

Farui

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