[Mne_analysis] Advantages of using "average EEG reference" in mne_browse_raw?

[Yury Petrov]

Hi Andres,

In physics the reference point for electric potentials is usually  
chosen to be in the infinity, which is a nice choice, because it is  
unique and makes sense otherwise. However, choosing reference point on  
the head surface is necessary to remove electrical environmental noise  
from EEG. To simplify matters, let's assume that EEG activity recorded  
on the scalp reflects only the neuronal activity in the (small)  
underlying part of cortex. By using referencing you effectively  
compare the activity under a given electrode with activity elsewhere  
in cortex. What is better for your purpose: to compare it with average  
cortical activity, or with cortical activity in the vicinity of your  
reference electrode(s)? It's up to you to decide, really. In practical  
terms, referencing to one or two electrodes means that signal on  
nearby electrodes will be weaker and, thus, less informative than on  
remote electrodes. Also, keep in mind that the particular choice of  
reference is immaterial for source localization: the result will be  
the same.

Best,
Yury

On Mar 5, 2009, at Mar 5, 2009 | 5:18 PM, Andres Felipe Salazar Gomez  
wrote:

> Hi MNE users,
>
> This might sound a very naive question but I will ask it anyway  
> since I
> want to have it clear in order to avoid affecting all my analysis:
>
> When calculating the average signals in mne_browse_raw or  
> mne_process_raw
> I have the option of turning off the projection (usually the average  
> EEG
> reference). The basic idea of an average EEG reference seems to be a
> reasonable thing to do. Nevertheless, doing this changes, sometimes  
> very
> drastically, the waveforms.
>
> How strong would anyone recommend me to use the average EEG reference?
> Is there any situation in which using the average EEG reference is  
> not the
> appropriate path to follow?
>
> Thank you very much for your collaboration,
>
> -- 
> Andres F. Salazar
> Research Technologist
> Neuroscience Statistics Research Laboratory
> asalazar at nmr.mgh.harvard.edu
> 149 13th Street, Room 4005
> Charlestown, MA  02129
> _______________________________________________
> Mne_analysis mailing list
> Mne_analysis at nmr.mgh.harvard.edu
> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/mne_analysis