[FieldTrip] EEG reference

[Rodrigo Montefusco]

NeuroBoludo!!

welcome!

this is (I think) a book you have to read if you are working in EEG (at
least some chapters). It's from Paul Nunez
Electric Fields of the Brain: The Neurophysics of EEGIf you need more info
about authors, just write me an email.

Good to know about you! a big hug!


Y



On Tue, Jun 26, 2012 at 7:23 AM, Stephen Politzer-Ahles <
politzerahless at gmail.com> wrote:

> Eduardo,
>
> Steve Luck's (2005) book *An Introduction to the Event-Related Potentials
> Method* has a chapter discussing reference methods. If you search the
> archives of the EEGLAB mailing list there are also many recent discussions
> (including references) about this issue.
>
> I am not personally experienced with spectral analyses, but in general,
> the online reference you use during the recording does not matter very
> much, since you can re-calculate the data to any other reference offline.
> For example, in both labs where I have done experiments, we use various
> online references but always re-reference to the average of both mastoids
> during the offline analysis; this is a common procedure, if you want to do
> that all you need to do is make sure to buy a cap that includes mastoid
> electrodes. Another common procedure is to use the average reference (see
> Luck (2005) or the EEGLAB online wiki for detailed discussion about average
> reference); for that, the most important thing is for the cap to have
> sufficient electrodes, evenly covering enough of the head. Of course, there
> are also many other referencing procedures available.
>
> Best,
> Steve Politzer-Ahles
>
>
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Mon, 25 Jun 2012 12:09:35 -0300
>> From: Eduardo Schenberg <eduardoschenberg at gmail.com>
>> To: fieldtrip at science.ru.nl
>> Subject: [FieldTrip] EEG reference
>> Message-ID: <7D53A322-3BF0-46F4-8D4B-B72E5B973EEC at gmail.com>
>> Content-Type: text/plain; charset=us-ascii
>>
>>
>> Hello all,
>>
>> I am new to this list, as I just started ding EEG experiments. I did some
>> pilot tests with a BrainProducts/Brain Vision with an Acticap and I am
>> doing some preliminary analysis using EEGLab/fieldtrip. I am now planning
>> to buy my own EEG form Brain Products, but I am bothered by the fact that
>> in most cap configs they sell, the reference is near Cz, usually FCz. As
>> far as my knowledge goes, if I want to study power spectrum alterations and
>> coherence in different frequencies between different electrodes, a
>> reference in the head can be a problem, specially if some of the regions of
>> interest are synchronous with the reference itself in the given frequency
>>
>> Can anyone point me to some good review or chapter about these issues so
>> I can study them better and buy the best config available?
>>
>> Many many thanks for all
>>
>> eduardo schenberg
>>
>>
>>
>>
>>
>> ------------------------------
>>
>> Message: 2
>> Date: Tue, 26 Jun 2012 11:31:32 +0200
>> From: Marcel Heers <marcel.heers at googlemail.com>
>> To: fieldtrip at donders.ru.nl
>> Subject: [FieldTrip] Source localization using DICS for EEG data from
>>        combined MEG/EEG recordings
>> Message-ID:
>>        <CAMq9WnPig4WAhsiM5ogwnXrPcPWj34TyWv8JuTAus5f=
>> xNecrA at mail.gmail.com>
>> Content-Type: text/plain; charset=ISO-8859-1
>>
>> Dear all,
>>
>> I am trying to perform source localization in the frequency domain
>> from EEG data using DICS. The data were recorded combined with MEG
>> (Neuromag data format).  The volume conductor is a 3 shell realistic
>> head model created with bemcp.
>> When running DICS with the following settings
>>
>> cfg                   = [];
>> cfg.method       = 'dics';
>> cfg.grad            = elec;
>> cfg.frequency    = 14;
>> cfg.vol              = vol_eeg;
>> cfg.dics.projectnoise = 'yes';
>> cfg.dics.lambda       = 5;
>> source = ft_sourceanalysis(cfg, freq);
>>
>>
>> I am am getting the following error message:
>>
>> ??? Error using ==> svd
>> Input to SVD must not contain NaN or Inf.
>>
>> Error in ==> beamformer_dics>pinv at 568
>>  [U,S,V] = svd(A,0);
>>
>> Error in ==> beamformer_dics at 314
>>        filt = pinv(lf' * invCf * lf) * lf' * invCf;              %
>> Gross eqn. 3, use
>>        PINV/SVD to cover rank deficient leadfield
>>
>> Error in ==> ft_sourceanalysis at 584
>>      dip(i) = beamformer_dics(grid, sens, vol, [],
>> squeeze(Cf(i,:,:)), optarg{:});
>>
>>
>> and I am not sure what might be the cause.
>>
>> Maybe anyone can help me! Thank you in advance!
>>
>> Marcel
>>
>>
>> ------------------------------
>>
>>
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>> End of fieldtrip Digest, Vol 19, Issue 42
>> *****************************************
>>
>
>
>
> --
> Stephen Politzer-Ahles
> University of Kansas
> Linguistics Department
> http://www.linguistics.ku.edu/
>
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