How to estimate the positions of 64 EEG channels from 19 EEG channels position that has been digitized?

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I have acquired EEG data using a 64 channel cap and I have digitized only 19 EEG channels. I would like to estimate the position of the rest of the channels using the EEG positions of the digitized 19 channels. I do have the MRI of the subjects.

Is this possible?

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hi @hmkhoo

Brainstorm does not have a dedicated interface for this particular case.

However, you can use a standard 64-channel cap template (provided by the manufacturer or available in Brainstorm), and then align it to your subject using the 19 digitized electrodes.

Concretely:

  • Load the full 64-channel template

  • Compute a registration (rigid transformation) between the 19 digitized electrodes and their corresponding positions in the template

  • Apply this transformation to the entire 64-channel template

This gives you an estimated position for the missing electrodes on the subject’s head.

If you also have the MRI, you can then project these electrodes onto the scalp surface for better anatomical accuracy.

You can also use the recent Brainstorm features for 3D scanners that help the digitization process.

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Hi tmedani,

Thank you for your kind response.

Would you mind to tell me how to compute a registration (rigid transformation) between the 19 digitized electrodes and their corresponding positions in the template?

Is there such an interface for this in Brainstorm?

Thank you.

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Hi @hmkhoo

Can you have a look here :

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Hi tmedan,

Thank you for the information.

I have tried the methods in the tutorial you have sent.

It does not provide a rigid transformation; rather, it applies the location of the 19 electrodes that I have digitized to the EEG recording from all 64 electrodes.

The location remains to be [0,0,0] for the remaining 45 electrodes.

Could you please explain me if there is anything else that I can try?

Thank you.