[Eeglablist] Re-referencing -- do I need to?

Joseph Dien jdien07 at mac.com
Mon Jul 26 17:24:07 PDT 2010

You might find my paper on the average reference to be of interest too.

Dien, J. (1998). Issues in the application of the average reference: Review, critiques, and recommendations. Behavior Research Methods, Instruments, and Computers, 30(1), 34-43.

Short answer is that not having the channel with the mastoid voltages (really, the channel with their differences) just means that you lost the information in those two channels.  It doesn't really affect the decision on whether to shift to a different reference scheme.

Average reference will definitely give you a different result.  Whether it is warping the waveforms compared to the mastoids reference or whether the mastoids reference is warping the waveforms compared to the average reference depends a lot on your montage is relative.

The big questions are how many electrodes did you use and how well did they sample the scalp surface?
Also, how do you plan to analyze and interpret the resulting data?



On Jul 15, 2010, at 2:24 PM, Nick Bedo wrote:

> Hi everyone,
> My recordings were referenced to both mastoids, but I don't have a channel that contains those data.  Is re-referencing advised/necessary in my case?  I was playing around with re-referencing to the average, and it really warps the waveform amplitudes compared to the ERPs calculated with our original methods.  Any input would be helpful.
> Thanks in advance,
> Nick
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Joseph Dien,
Senior Research Scientist
Center for Advanced Study of Language
University of Maryland 
7005 52nd Avenue
College Park, MD 20742-0025

E-mail: jdien07 at mac.com
Phone: 301-226-8848
Fax: 301-226-8811

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