[Eeglablist] Problem importing .eeg -Files and rereferencing data

[Stephen Politzer-Ahles]

Hi Matthias,

loadeeg() is actually for loading Neuroscan files, not Nihon; it's a little
confusing because these and several other systems all use ".eeg" as their
file extension. So your first error is probably because of this. I don't
have experience working with your data format, but see
http://sccn.ucsd.edu/pipermail/eeglablist/2008/002341.html .

As for your referencing issue, I'm not sure what could be causing the error
(could you give a little more specific information about exactly what
commands you have used?). If you're having trouble renaming channels, my
guess is you will have better luck using pop_chanedit() (Edit > Channel
Info in the graphical user interface) rather than pop_chanplot(). I just
wanted to point out, though, that I calculating average reference is
usually not recommended when you have only a small number of
electrodes--see the discussions in
http://sccn.ucsd.edu/wiki/Chapter_04:_Preprocessing_Tools#Re-referencing_the_dataor
in Luck (2005).

Best,
Steve

On Wed, Nov 7, 2012 at 7:22 AM, Wittayer, Matthias <
wittayer at students.uni-mainz.de> wrote:

> Dear experts,
>
>
>
> we have several problems analyzing our Dataset acquired by our Nihon
> Kohden 2100- System with just very few channels recorded referenced to Fz.
> We normally use BESA for analysis of our data, but however it doesn't work
> for a dataset with just a few channels, so we switched to EEGLAB and are
> very contented with its different features.
>
> The problems which occured are:
>
> The data is saved as .eeg- files. Importing it to EEGLAB produces an error
> (EEGLAB error in function loadeeg() at line 237: Undefined function or
> variable "chan_names".) useing default settings. Since I am not able to
> reconstruct in which way the variable is declared in this routine, I am not
> able to troubleshoot. We already tried to modify settings of the import-
> dialogue but failed. So we converted .eeg - Data to .edf- files and it
> worked out quite well.
>
> Now a new problem occured while rereferencing our data to linked mastoids
> (or at least trying to do so). The rereferencing routine works out fine for
> average reference but trying to rereference the data to any channel
> produces the error-message "Channel EEG not found".
>
> I assume, that these problems (at least the second one) occur because of
> our channel's names (they are coded such as "EEG Fp1" with a space
> character in between to discriminate them from Triggerchannels). We already
> tried to rename the channels but did not succeed (pop_chanplot) because the
> "rename selected channel"- procedure was not available. So we tried to
> rename them manually but failed again.
>
> In tutorials and troubleshooting- sites I was not able to find a problem
> similar to ours. All trying to solve it failed up to now.
>
> Does anybody else have similar problems? How can we rename our channels
> properly so we can rereference our data to these channels? And does this
> work useing the imported edf- data as well? How can we import our .eeg-
> Data directly?
>
> We would be grateful for some guidance or hints how to proceed.
>
>
>
> Kind Regards
>
>
>
> Matthias Wittayer,
>
>
>
> Mainz, Germany
>
> wittayer at students.uni-mainz.de<mailto:wittayer at students.uni-mainz.de>
>
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-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://people.ku.edu/~sjpa/
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