[Mne_analysis] Large mean voltages in BEM EEG forward model.

[Yury Petrov]

I think that the MNE forward matrix is just the distribution of  
potentials on your electrodes produced by a current dipole at a given  
location times all such locations. There is no reason for the sum of  
potentials over the electrodes to be always 0. For example, if the  
electrodes cover mostly the area of the scalp to where one pole of the  
dipole points, then the averaged potential will be quite different  
from zero. You could add a constant potential to turn the average to  
zero, but this would only work for one dipole out of many.

On Sep 30, 2008, at Sep 30, 2008 | 3:54 PM, Justin Ales wrote:

> Hi,
>
> I've been looking at the forward computations generated by MNE.  I've
> been generating my fif files from data I have in matlab. I have an
> average reference montage, and when I look at the forward model there
> are large variations in the average across channels.  Since it is an
> average reference montage I expected the forward model to have zero
> mean. I'm not sure if I don't understand the forward model output from
> MNE, or if I'm not importing my data correctly.
>
> Thanks,
> Justin Ales
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