reference electrode

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caranico
Posts: 7
Joined: 11 Oct 2011, 04:33

reference electrode

Post by caranico » 02 Oct 2012, 05:37

Hello everybody!
i want to collect opinions on where is the best position for placing the reference electrode.

Recording with a reference electrode (for example ear-lobe or mastoid) and then use CAR is right?
Thank you

mellinger
Posts: 1065
Joined: 12 Feb 2003, 11:06

Re: reference electrode

Post by mellinger » 02 Oct 2012, 08:32

Hi,

when you plan to use a Common Average Reference, or Laplacian spatial filter, the contribution due to placement of the reference electrode will be removed by that filter, as long as signal quality is good. Placement of the reference electrode then only matters with regard to recording quality, i.e. it should be placed at the head, and not too close to sources of artifacts (eyes and muscles). Thus, ear-lobe or mastoid is optimal.

Note however that asymmetric placement of the reference electrode will result in asymmetries in the unfiltered signal. To be able to analyze the unfiltered signal, you may eiher choose to use a central position such as AFZ for the reference electrode, or to physically connect electrodes at both locations to the amplifier's reference input (e.g., "linked mastoids").

Regards,
Juergen

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