[FieldTrip] Amplifier for EGI-data in fieldtrip???

Matt Mollison matt.mollison at gmail.com
Thu Sep 6 19:01:42 CEST 2012


Joe,

A few related questions:

Does using the "calibrate data" option when exporting to raw (simple
binary) correct for gain? Or is there a different solution/recommendation?
Does exporting to MFF (Net Station 4.5.x only) or EGIS have this issue? I
tend to use EGIS (faster to read than raw) and have no recollection of
seeing unusually large voltages.

Thanks,
Matt

--
Univ. of Colorado at Boulder
Dept. of Psychology and Neuroscience
matthew.mollison at colorado.edu
http://psych.colorado.edu/~mollison/

On Wed, Sep 5, 2012 at 7:17 PM, Joseph Dien <jdien07 at mac.com> wrote:

> The Simple Binary (.raw) files don't get corrected for gain when imported
> (I helped write them).  I've experienced occasional unpredictable bugs with
> NetStation export routines where the files are generated with amplitudes
> many times too large, even with text format files.  It's a bit
> disconcerting to say the least.  I could take a look at your files if you'd
> like confirmation.
>
> Joe
>
> On Sep 4, 2012, at 4:00 PM, Ingrid Nieuwenhuis <inieuwenhuis at BERKELEY.EDU>
> wrote:
>
>  Hi Daria,
>
> Also, did you try looking at your raw data (so before the ERPs are made)
> in FieldTrip and in Net Station? So open your .raw data in NetStation. You
> can just look at a random participant's data, and check if the scale is the
> same. I'm pretty sure no amplification takes place when reading in the data
> into FieldTrip, this check can confirm that. Hope this helps, and let us
> know what you find.
>
> Cheers,
> Ingrid
>
>
> On 9/3/2012 1:35 PM, Robert Oostenveld wrote:
>
> Hi Daria,
>
>  There might indeed be an incompatibility in the gain  value applied to
> the data.
>
>  If you are able to export the data using the EGI software in another
> format (e.g. EDF), you could read them both into FieldTrip and compare the
> timecourse aplitudes to check whether they are different. In case they are,
> I suggest to involve EGI support. They are aware of the FieldTrip reading
> functions and will know much more about the internals of their various file
> formats.
>
>  best regards
> Robert
>
>
>
>
>  On 3 Sep 2012, at 17:22, Daria Laptinskaya wrote:
>
> Dear Fieldtrippers,
>
> I analysed EGI-data (.raw-files, NetStation 4.3.) with the fieldtrip
> toolbox.
> The ERPs look perfect.
> The 'only' problem is, that my signals look to strong.
> It looks like if I get amplitutes (average) until 70 ┬ÁV.
> I think it must be an intern amplifier for the signals.
>
> Does anyone know this problem with EGI-data?
>
> Or does anyone know, where I can see the amplifier?
>
>
>
> Greetings,
> Daria _______________________________________________
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>
>
>
>
> _______________________________________________
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>
>
> --
> Ingrid Nieuwenhuis PhD
> Postdoctoral Fellow
> Sleep and Neuroimaging Laboratory
> Department of Psychology
> University of California, Berkeley
> California 94720-1650
> Tolman Hall, room 5305
>
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>
>
>
>
> --------------------------------------------------------------------------------
>
> Joseph Dien,
> Senior Research Scientist
> University of Maryland
>
> E-mail: jdien07 at mac.com
> Phone: 301-226-8848
> Fax: 301-226-8811
> http://joedien.com//
>
>
>
>
>
>
>
>
>
>
>
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