BioSemi.nl

Hi. I'm using Biosemi ActiveTwo system.

I'm going to make an experiment environment for P300 speller, and I want to use the average signals from the two mastoid for referencing.

Now I have some questions.

If I placed CMS and DRL electrodes on each mastoid, does it mean that the average signals from the two mastoid will be used for referencing? If it is not correct, I should use other electrodes for referencing. Then, How can I set the reference channel in the Matlab. Is there any functions or variables in the code(InitBiosemi.m)?(I can easily find reference menu from the ActiView, but I usually use Matlab for making environment of experiments.)


In summary, how can I use the average signals from the two mastoid to be used for referencing in the Matlab?

Use two extra electrodes (for example: EX1 and EX2) on the mastoids. In your file reading software, use the average of these two extra channels as the reference for the scalp electrodes. Locate CMS and DRL on the scalp.

The "CMS/DRL as a reference" issue has been discussed extensively here, please use the search function.

Best regards, Coen (BioSemi)

Yes you need to utilize additonal electrodes as the reference, I do this.