[Eeglablist] Re-Referencing Question

[Robert Lawson]

Earlier in the thread, someone mentioned the problems with ear 
reference. I have read some theoretical papers claiming that linking the 
ears leads to a shunt and thence to inaccurate data. However, all the 
empirical studies I have seen found no difference between mathematically 
and physically linked ears. Does anyone know of any empirical data that 
shows physically linked ears are at all different from mathematically 
linked ears?

Robert Lawson

Joseph Dien wrote:

> 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
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