Referencing to all electrodes

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Referencing to all electrodes

Post by Judiths » Wed Sep 22, 2010 8:53 am

Hi all,

I just started an EEG project, and we're using a Biosemi 128 system.
Right now, we're using two external electrodes on the mastoid bones as references. I understand why references are required, and how to use them.
But in line to what my collegues have been doing we're also choosing the Reference to all 128 electrodes option in the Reference dropdown box in ActiView. I do not get how an online recording can be referenced to all 128 electrodes? And does it still make sense to use the externals as references as well?

Tips and clarification are both welcome!

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Post by Coen » Thu Sep 23, 2010 11:41 am

Referencing to all 128 electrodes means that each signal (voltage) is difference between the potential of a certain electrode and the average potential of all 128 electrodes. The reference is the potential at a virtual point in the center of all 128 electrodes.

Best regards, Coen (BioSemi)

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