Fwd: [FIELDTRIP] Reference electrode in lead field

[Robert Oostenveld]

Begin forwarded message:

> From: "Dr. Georges Otte" <georges.otte at telenet.be>
> Date: 1 October 2009 13:49:13 GMT+02:00
> To: r.oostenveld at FCDONDERS.RU.NL
> Subject: reference
>
> ...
> I have followed the discussion on reference and already contacted
> Dien. I agree but what about non ERP data ? Phase information and
> coherence. Can we safely use the averaged common reference for that.
> Robert Thatcher (neuroguide) quoting rappelsberger is opoosed to it
> and shows in his neuroguide package that in small channel systems
> (19-22) a ACR scrambles phase information between channels.
>
> Sincerely
>
> Dr. Georges Otte
> P.C dr. Guislain instit
> Gent
> Belgium
>
>
> PS How can I get back on the list ?
>
> Ransscipt
> no problem!  I haven't been working in the frequency domain and am
> not very familiar with spectral analyses so I can't say.  Sorry!
>
> Joe
>
>
> On Sep 30, 2009, at 2:20 AM, Dr. Georges Otte wrote:
>
>
> If the reference is not close to zero (fi using an average reference
> on to low an electrodeset fi 19 ch with prefrontal channels likely
> to be contaminated by occasional quite lagre eye blink or eye
> movement artifacts) what would be the effect on phase calculations ?
> From point to point the reference value that is substracted from
> each channel would be different from zero. Would that not wreck
> havoc to interchannel phase information or post stimulus coherence
> mapping ? Untrusthworthy ?
>
> Same qyuestion: if people use PCA or ICA to eliminate these
> artifacts and inverse reconstruct their EEG, can they still rely on
> phase calculations without errors ?
>
> Sincerely,
>
> Georges Otte
>
> PS Sorry to mail You personally but for some reason (perhaps change
> of email adres or long period of inactivity ) I seem to be  cutoff
> from the fieldtrip listserv
>
>


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