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

[Daniel Goldenholz]

People that read EEG "by hand" use multiple references because it gives
different views of the data.
That is because humans can't see the physics.

Daniel Goldenholz MD, PhD
--------------------------------------------------------
http://www.nmr.mgh.harvard.edu/~daniel


On Thu, Mar 5, 2009 at 5:40 PM, Yury Petrov <y.petrov at neu.edu> wrote:

> 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
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>
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