[Eeglablist] online reference

[Brittany Alperin]

Thanks Andreas

To clarify, I have 31 channels + ref (Cz) + ground. So 33 in total. I don't
expect to see the ground, so I'm really only "missing" Cz. I added Cz to my
channel locations and selected "add current reference channel back to data"
without re-referencing to anything else. I can now see Cz, but it isn't a
flat line. Am I incorrect in thinking that it should be totally flat?

Thanks,
Brittany

On Thu, Apr 23, 2015 at 5:29 AM, Andreas Widmann <widmann at uni-leipzig.de>
wrote:

> Hi Brittany,
>
> this sounds like two different problems:
> If you record from 32 channels + Ref + Ground the imported file should
> have 32 channels (but not your Cz Ref channel). Please reconfirm that your
> Pycorder setup really records from 32 data channels (34 electrodes). In
> case there is really a channel missing, please, submit a bug report to the
> bugtracker including a short sample file.
>
> If you want to keep the implicit online reference (Cz) as a new channel
> after re-referencing the data to another channel you have to use the „Add
> current reference channel back to the data“-option (GUI; 'refloc‘ on
> command line). To use this option you have to first append a (Cz-) channel
> in the GUI channel editor (appearing in EEG.chaninfo.nodatchans) which you
> can subsequently select during re-referencing. The „new“ Cz-channel is the
> inverse of the channel the data were re-referenced to (now missing in the
> data or being flat if "Retain old reference channels in data“ was selected).
>
> Please note that the „Add current reference channel back to the
> data“-option should not be used for systems where common mode rejection is
> applied offline (e.g. Biosemi).
>
> Hope this helps,
> Andreas
>
> > Am 22.04.2015 um 21:59 schrieb Brittany Alperin <balperin07 at gmail.com>:
> >
> > Hello
> >
> > I'm using a 32 channel brain vision system and am recording with
> PyCorder. When I import my data using the brain vision recorder plugin,
> only 31 channels are present. I'm recording with Cz as an online reference
> and Cz is the channel that is missing. I can re-reference, but Cz is still
> absent.
> >
> > Has anyone had an issue with recording with an online reference and not
> having that data import into EEGlab? Or does anyone have a different way to
> import brain vision data?
> >
> > Thanks,
> > Brittany
> >
> >
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