[Eeglablist] Re-Referencing Question

[Joseph Dien]

The only way to get an estimate of the left ear reference site activity  
is to compute an average reference but since, as you say, there are not  
enough channels, you would end up improperly imputing common activity  
at the recording sites to the reference site as well.  If you want to  
rereference to a mean ear reference, you add the left ear channel to  
the data array (the left ear referenced to itself is a flat line of  
zeros) and then subtract the mean of the left and right ear channels  
from the entire array.  You should be able to do this manually in  
Matlab if eeglab isn't set up to do this yet.  You might want to read  
my paper on referencing for more info:

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

Cheers!

Joe

> Our specific eeglab question relates to how (or maybe if), using
> eeglab's re-referencing pop-up window, both the above recording options
> could be correctly rereferenced to mathematically linked ears while
> obtaining/maintaining a recorded signal for all six locations Cz, C3,
> C4, Fz, F3, F4. The re-referencing window allows one to enter one or
> more (at least it appears that more than one can be used) channel
> number(s) for the new reference but in the above scenario (a) the left
> and right ears are not both available as channel numbers (for obvious
> reasons because Le ear was the reference).
>


------------------------------------------------------------------------ 
--------

Joseph Dien
Assistant Professor of Psychology
Department of Psychology
2007 Percival Stern Hall
Tulane University
New Orleans, LA 70118-5698

Office: Room 3061
Phone: (504) 862-3300
Fax:   (504) 862-8744
E-mail:jdien at tulane.edu
www: http://www.tulane.edu/~jdien/Dien.html

Starting Fall 2003:
Department of Psychology
426 Fraser Hall
1415 Jayhawk Blvd
University of Kansas
Lawrence, KS 66045-7556
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