Re-referencing 128 EEG data to averaged mastoids

Hi, I have 128 channels EEG data recorded with reference Cz. The data also have A1 and A2 electrodes. Now I want to re-reference the recordings to averaged mastoids and reduce to 10-20 system (19 electrodes) from 128 electrodes. How I can do this in matlab?

Thanks Hafeez

Answer 1

[Star Strider]

That takes far more knowledge of the technology of EEG recording than I have, so I can’t help you on the technical details. You would likely first have to re-reference them and then interpolate to estimate the potentials at the 10-20 sites. Perhaps the File Exchange contribution eegplot can give you some ideas.

I would go to the software on the equipment you used to acquire your EEG data to see if it has the capability to re-reference your records and remap them to the 10-20 system.

[Hafeezullah Amin]

Thanks for reply. We have EGI netstation software and it can be re-reference to mastoid as it have the A1 and A2 channels.

[Star Strider]

My pleasure!

If you can have it re-reference your EEG, you can then use interpolation (that MATLAB can do reasonably easily) to do the interpolation to estimate the electrode potentials of a 10-20 system.

It would first be necessary to know if any nonlinearities due to tissue conductivity have to be accounted for in the interpolation, or if you could simply do relatively straightforward (perhaps linear) interpolation. With your current data being from a 128-electrode recording, you can likely do linear interpolation to your 10-20 sites. However, I would use the information in eegplot to guide your choice of interpolation methods.