[FieldTrip] Missing triggers with Biosemi EEG data

Vladimir Litvak litvak.vladimir at gmail.com
Thu Mar 1 16:02:28 CET 2012

Dear Mark,

I'm not sure what the reason is for not supporting downgoing triggers
in Biosemi, but there probably is one. I'm CCing your message to
Fieldtrip mailing list where it might be better answered. Are you sure
that the missing triggers are recorded correctly? Can you see them
with any other software you have? Sometimes there is a problem with
connectors which leads to incorrect assignments of trigger codes.


On Thu, Mar 1, 2012 at 2:54 PM, Mark Schram Christensen <markc at drcmr.dk> wrote:
> Dear Vladimir Litvak
> I am currently analysing some EEG data with SPM8 obtained with the biosemi
> system, and I am missing quite a lot of my triggers. I get the warning
> that only upcoing flanks are supported for biosemi, and I suspect that
> that is the reason. I can see that the status channel changes when ever I
> should have had the trigger.
> I guess it is related to the field trip file ft_read_event.m, which seems
> to have this biosemi exception, that even though it should look for both
> up and down flanks it only finds up with biosemi.
> Do you know if there is a possibility of also getting downflank triggers?
> Looking forward to hear from you.
> Best wishes
> Mark Schram Christensen
> _______________________________________________
> Mark Schram Christensen, MSc, PhD
> Copenhagen Neural Control of Movement &
> Danish Research Centre for Magnetic Resonance
> Department of Exercise and Sport Sciences
> Copenhagen University Hospital Hvidovre
> KettegÄrd Allé 30
> DK-2650 Hvidovre
> Phone: +45 3862 3407
> E-mail: markc at drcmr.dk
> http://www.ifi.ku.dk/
> http://www.cph-ncm.ku.dk/
> http://www.drcmr.dk/markc

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