How can I manually set a reference electrode from the Brainstorm interface?

[Francois]

I am a new Brainstromer, and I would like to know if it is possible for me to set manually a pair of electrodes from my custom Emotiv EPOC+ EEG cap as 2 reference channels.

If you want to re-reference your EEG recordings to the average of the P3+P4 electrodes:

• For display (linked ref): https://neuroimage.usc.edu/brainstorm/Tutorials/MontageEditor#Re-referencing_montage
• For further computations: https://neuroimage.usc.edu/brainstorm/Tutorials/Epilepsy#Average_reference

Now, I would like to compute a head model using DUNEuro FEM (volume) that generates a 14-rows Gain matrix, with the two missing rows corresponding to P3 and P4.

The EEG inverse solutions are always computed from EEG recordings in average reference. No matter which referencing scheme you transform your data into before, the data will be re-converted to an average reference before the computation of the minimum norm solution.

Reference of the gain matrix - EEG OPENMEEG BEM in Brainstorm

Hi Rasheeda, This depends of what you are doing. The forward models (the .Gain fields) that are produced by Brainstorm and OpenMEEG are calculated for an arbitrary reference. It doesn't matter much what reference you are using as long as you are using the same for the EEG recordings and the forward operator. Before using this Gain matrix, you need to convert it to the same type of reference your recordings are using. Because it's quite complicated in terms of interface to handle multiple re…