[FieldTrip] Reading in .bdf files

Nishant Jain N.Jain at tudelft.nl
Fri Oct 10 14:10:30 CEST 2014

Hi Ricarda,

I’m currently using .bdf files. EXG is for external signals like eye blinks or even EMG.

You want to ideally remove the really bad channels from your signals first, then re-reference them to all electrodes (common average rereferencing).

The really high vertical scale you’re seeing is due to digital trigger signals, I think.

Just get rid of EXG, GSR etc electrodes, keep only the EEG electrodes. Then proceed with channel/trial rejection!

Best of luck,

Nishant Jain.
TU Delft, Netherlands.

From: fieldtrip-bounces at science.ru.nl [mailto:fieldtrip-bounces at science.ru.nl] On Behalf Of Raquel Bibi
Sent: dinsdag 23 september 2014 16:34
To: FieldTrip discussion list
Subject: Re: [FieldTrip] Reading in .bdf files

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?



On Mon, Sep 22, 2014 at 10:43 AM, Ricarda Braukmann <r.braukmann at donders.ru.nl<mailto: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 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<mailto:r.braukmann at donders.ru.nl>

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