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Location of CMS/DRL electrodes
Posted: Thu Sep 09, 2004 6:21 pm
by ales
Our group is interested mainly in signals generated from the visual areas in the occipital lobe. So I was wondering what the best placement of the CMS/DRL electrodes is to optimize the the signal from the electrodes in the back of the head.
Justin Ales
Posted: Wed Sep 15, 2004 12:48 pm
by Coen
The best Common Mode rejection is achieved for electrodes close to the CMS electrode. So, in your application, the best location of the CMS electrode would be the back of the head. The DRL electrode can be located anywhere on the body.
In practice, the location of the CMS and DRL electrodes is not very critical because the slightly higher Common Mode voltage for electrode located far away from the CM electrodes is still effectively canceled during the reference process (reference signal is subtracted from electrode signals, see
http://www.biosemi.com/faq/cms&drl.htm).
Beware of a gel bridge between CMS and DRL electrodes, since this would reduce the total CMRR with 40 dB (do not place the CM and DRL too close together).
Best regards, Coen