[Eeglablist] Doubt about provided data (first analysis)

Tue Mar 19 10:42:02 PDT 2013

Dear Juan,

I downloaded your data to replicate the problem. I could not. It just
worked. Follow these steps.

1. Download the latest version of EEGLAB.
2. File - Import data - Using EEGLAB functions and plugins - From Neuroscan
.cnt file

I saw your photos. Apparently you failed in importing the data.

Makoto

2013/3/19 Juan Carlos Haro Vicente <jharovicente at gmail.com>

> Dear Makoto;
>
> I am thinking that the data provided is not correct. Trying what you
> said I obtain next results:
>
> http://www.flickr.com/photos/94067049@N03/8572065878/
>
> And, if we focus on channels one by one, we can see a different
> between odd and couple channels:
>
> http://www.flickr.com/photos/94067049@N03/8572065998/
>
> http://www.flickr.com/photos/94067049@N03/8572066088
>
> After filtering:
>
> http://www.flickr.com/photos/94067049@N03/8572066054
>
> http://www.flickr.com/photos/94067049@N03/8572065968
>
> http://www.flickr.com/photos/94067049@N03/8572065936
>
> I have asked the person who gave me the data and they said this is a
> valid EEG signals. Maybe, It is because the way I use for importing,
> those are .CNT files and I am only able to import them using "From
> other formats using FILE-IO toolbox" and then I obtain next warning:
>
>
> ------------------------------------------------------------------------------------------------------------------------------------------------------------
> Warning CNTOPEN: month and day were mixed up 2007-15-5-13-17-37
> WARNING SOPEN(CNT): OVERFLOWDETECTION might not work correctly. See
> also EEG2HIST and read
>    http://dx.doi.org/10.1016/S1388-2457(99)00172-8 (A. Schlögl et al.
> Quality Control ... Clin. Neurophysiol. 1999, Dec; 110(12): 2165 -
> 2170).
>    A copy is available here, too:
> http://pub.ist.ac.at/~schloegl/publications/neurophys1999_2165.pdf
> Warning CNTOPEN: month and day were mixed up 2007-15-5-13-17-37
> Reading data in CNT format...
> Warning SREAD(CNT): could not read 2.053672e+006 samples, only 2053672
> samples read
>
> ------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> I have uploaded one of these files to dropbox in case someone wants to see
> it:
>
> https://www.dropbox.com/s/9an7cl7mhzv8smx/isabel_parp_correg.cnt
>
> Regards and thanks again
>
> Juan Carlos
>
>
>
> 2013/3/19 Makoto Miyakoshi <mmiyakoshi at ucsd.edu>:
> > Dear Juan,
> >
> > Amplitude level of -110 dB/Hz^2 is like 100000 times smaller than my
> data.
> > Something is wrong.
> >
> > Please follow these steps for diagnosis.
> > 0. make sure you are using the latest EEGLAB
> > 1. import your data straight from your raw data
> > 2. copy and paste these lines
> >
> > figure; bar(std(EEG.data,0,2));
> >
> > This is to see standard variation for all channels. In the plot, the
> unit is
> > microvolt.
> >
> > figure; plot(EEG.data(1,:))'
> >
> > This is to see time series of one channel. Here 1 is channel number.
> Change
> > it to other channels to see the difference. In the plot, the unit is
> > microvolt.
> >
> > 3. apply 1 Hz (0.5 is fine) high-pass for all channels and run the above
> > test 2 again.
> >
> > What do you see?
> >
> > Mikolaj's initial guess is right: if the data were DC recorded, the data
> can
> > contain huge baseline drift (several thausands) that can completely mess
> up
> > spectopo plots.
> >
> > Makoto
> >
> > 2013/3/15 Juan Carlos Haro Vicente <jharovicente at gmail.com>
> >>
> >> Dear EEGLAB list;
> >>
> >> This is my first post, I am a student from Spain who is doing a thesis
> >> about signal processing using EEGLAB. First of all, I want to say
> >> thank you for all the info and help that I found here. It has been
> >> provided to me data from different subjects in an experiment about the
> >> process of different languages. Once I export this data to EEGLAB I
> >> have 66 channels of information which look like EEG signals. I extract
> >> my epochs and here, it comes the problems. When I represent the
> >> channel spectra and maps it shows me next picture:
> >>
> >> http://www.flickr.com/photos/94067049@N03/8558863353/
> >>
> >> Which, as I think, it is very differents from what I have to expect.
> >> If I see a channel, I obtain what I think is normal:
> >>
> >> http://www.flickr.com/photos/94067049@N03/8559971178/
> >>
> >> And the channel ERP scalp map shows me a signal without sense:
> >>
> >> http://www.flickr.com/photos/94067049@N03/8558863377/
> >>
> >> After seeing this, I continued with ICA analysis, once I did, I
> >> obtained next result for spectra maps:
> >>
> >> http://www.flickr.com/photos/94067049@N03/8559971126/
> >>
> >> Again, far away from what I expected. If I represent components ERP in
> an
> >> array:
> >>
> >> http://www.flickr.com/photos/94067049@N03/8558863349/
> >>
> >> where we can see what it looks like ERPs, but very contaminated by
> noise.
> >>
> >> After say my situation, I would like to ask you if you have any idea
> >> about what it is the problem with the data. I trust your experience
> >> with the software and good management of these situations
> >>
> >> Thank you very much
> >> Regards
> >>
> >> Juan Carlos Haro
> >> _______________________________________________
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> >
> >
> >
> >
> > --
> > Makoto Miyakoshi
> > JSPS Postdoctral Fellow for Research Abroad
> > Swartz Center for Computational Neuroscience
> > Institute for Neural Computation, University of California San Diego
>

-- 
Makoto Miyakoshi
JSPS Postdoctral Fellow for Research Abroad
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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