[FieldTrip] Reading in .bdf files

[Ricarda Braukmann]

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
>>>
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>>> fieldtrip mailing list
>>> fieldtrip at donders.ru.nl
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>>
>>
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>
>
>
>
-- 

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
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