[FieldTrip] Reading in .bdf files

[Raquel Bibi]

Hi Ricarda,
Some suggestions:
1. Did you include your EXG electrodes in the re-referenced channels?
Perhaps you could remove these?

2.Review and exclude bad channels before re-referencing?  I used the
Biosemi Viewer before analyzing the data in Fieldtrip.

3. Re-reference to a single channel, like CZ(A1).

I haven't worked with bdfs in a while, I had the same problems you're
describing initially with my data.  Here are a few solutions I remember
offhand.  I was able to resolve them without converting them to .cnt.

Best,

Raquel

On Tue, Sep 23, 2014 at 11:11 AM, Ricarda Braukmann <
r.braukmann at donders.ru.nl> wrote:

> Hi Rachel,
>
> Yes, I was wondering about the re-referencing because I indeed read that
> this was the necessary first step for Biosemi data.
> What would one usually re-reference the data to?
>
> I tried re-referencing to all electrodes (since no mastoid etc. has been
> collected) but this did not solve the issue for the .bdf file.
>
> It works for the converted .edf file in which the data looks much better
> from the start but I am not sure whether everything is going correctly.
> The data is quite noisy and also when trying to apply a high-pass filter
> later Matlab gives an error of unstable poles. I am not sure whether this
> is due to the actual properties of my data or whether it is still related
> to the way I read it in, so any suggestions are very welcome!
>
> Thanks a lot!
> Best,
> Ricarda
>
>
> On Tue, Sep 23, 2014 at 4:33 PM, Raquel Bibi <bibi.raquel at gmail.com>
>> wrote:
>>
>>> Hi Ricarda,
>>> The Biosemi system uses CMS & DRL during acquisition as the common mode
>>> for the ground electrode.   Are you re-referencing your EEG signals, before
>>> viewing them in ft_databrowser?
>>>
>>> Best,
>>>
>>> Raquel
>>>
>>> On Mon, Sep 22, 2014 at 10:43 AM, Ricarda Braukmann <
>>> r.braukmann at donders.ru.nl> wrote:
>>>
>>>> Hi everyone,
>>>>
>>>>
>>>> I have a question regarding reading in Biosemi .bdf files.
>>>>
>>>>
>>>> I followed the example on the ft website to read in a .bdf file, and -
>>>> although it does not give an error- , the data looks very odd. In the
>>>> ft_databrowser for example the vertical scale is [ -178000  178000 ]
>>>> which seems very werid to me.
>>>>
>>>>
>>>> I  tried re-referencing the data, like in the example, using channel
>>>> 'EXG5', but this did not help.
>>>>
>>>>
>>>> Is there anyone who has experience with reading in biosemi files who
>>>> could give me some advice?
>>>>
>>>> It would also be great if someone could explain to me what these EXG
>>>> channels are exactly.
>>>>
>>>>
>>>> I have for now turned to converting the .bdf file to .edf file (using
>>>> the converter from www.biosemi.com/download/
>>>> <http://www.biosemi.com/download/ToolsForRuntimeEngine861/Converter86.zip>).
>>>> Then the data looks normal, but it created some other issues with my
>>>> markers and I would rather not use the converted files.
>>>>
>>>> More than anything, I am very curious what is going on with the
>>>> original file, so any help is much appreciated!
>>>>
>>>>
>>>> Thanks in advance!
>>>>
>>>> Ricarda
>>>>
>>>>
>>>> --
>>>>
>>>> Ricarda Braukmann, MSc
>>>> PhD student
>>>>
>>>>
>>>> Radboud University Medical Centre & Baby Research Center
>>>>
>>>> Donders Institute for Brain, Cognition and Behaviour,
>>>> Centre for Neuroscience & Centre for Cognition
>>>>
>>>> Room B.01.22
>>>> Phone: +31 (0) 24 36 12652
>>>> Email: r.braukmann at donders.ru.nl
>>>>
>>>> _______________________________________________
>>>> fieldtrip mailing list
>>>> fieldtrip at donders.ru.nl
>>>> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>>>>
>>>
>>>
>>> _______________________________________________
>>> fieldtrip mailing list
>>> fieldtrip at donders.ru.nl
>>> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>>>
>>
>>
>>
>>
> --
>
> Ricarda Braukmann, MSc
> PhD student
>
>
> Radboud University Medical Centre & Baby Research Center
>
> Donders Institute for Brain, Cognition and Behaviour,
> Centre for Neuroscience & Centre for Cognition
>
> Room B.01.22
> Phone: +31 (0) 24 36 12652
> Email: r.braukmann at donders.ru.nl
>
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>
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