[Mne_analysis] Re-referencing EEG electrodes in MNE

[Alexandre Gramfort]

Hi Alan,

I moved the discussion to :

https://github.com/mne-tools/mne-python/issues/784

let me know if you want to give it a try.

> the raw stage, the rationale being that re-referencing might reduce the
> number of epochs that are rejected by amplitude threshold. I don't want to
> do this with an average reference, since I know that I have some noisy
> channels that I need to exclude.

you should mark your channels as bad first

> I was playing around with this yesterday and I came up with a crude
> solution. I've attached my python code.
>
> Although I eventually want to move to source modeling, right now I'm
> interested in using MNE to do ERP and spectral analysis, instead of using
> something Matlab based like EEGLAB. Would you recommend re-referencing in
> this context?

yes if you want to see something that matches the ERP topography

> While I'm on the subject, EEGLAB recommends specifying a reference channel
> when import eeg data from a .bdf file. Their rationale ...
>
> %                  WARNING! Biosemi Active II data
> % are recorded reference-free, but LOSE 40 dB of SNR
> % if no reference is used!. If you do not know which
> % channel to use, pick one and then re-reference after
> % the channel locations are read in. {default: none}
>
> Is this also a problem with mne_edf2fiff ?

I don't know. I guess it's due to limited precision used for storing
floating point values

hope this helps

Alex