Spurious response and comment triggers added

[alexander9]

Hi,
In my latest recording a lot of markers/triggers have been added. 100,000+ markers with "Comment Speed mode x" have been added to the last two blocks of my recording (out of 10 blocks). Moreover, thousands of response markers have been added although I do not have a response marker in my study. The stimulus markers which I sent and were part of the study are there as well.

However, I have no idea why these additional markers have been added. Moreover, because of the vast amount of markers added, the file becomes problematic. It struggles to open. Fuinctions such as Edit markers are not available as there is not enough memory

any advice on this would be much appreciated
bw,
alex

[Coen]

If you do not use response switches, then please check that the 5th line in your CFG is:

RespSwitch=0 //0: standard ergo, 1: ergo 1 & 2 coupled to trigger 9 & 10, 2: switch input coupled to trigger 9 & 10

If RespSwitch is on 1 or 2, without switches connected, then that could explain lots of spurious triggers on lines 9 and 10.

Best regards, Coen (BioSemi)

[alexander9]

Dear Coen,
Thanks for your reply. I've checked and this does not seem to be the problem, the RespSwitch = 0 in the CFG file.

However, I think the problem is something else, hardware or battery related. I have now tested two participant and it has happened twice. At around 5010 seconds these spurious markers are added. Mainly Comment markers and Speed Mode Markers. I tried to attach a file with the exported matrkers for Subkject 1 but apparently .txt extension not allowed here. What format can I upload? There is even a Batterry low marker which makes me think it could be the battery, but the battery was fully charged and the experiment is only a couple of hours.

I really do not know what to do and need to get this sorted asap
bw
alex

[Coen]

Since the CFG is correct, the far most likely cause is a problem with the optical link (error bits, but not enough to cause an sync error popup). You probably see a few spikes in the EEG channels too.

Try to blow out the optical transmitter and receiver with compressed air, and try to test with another optical fiber. If the problem remains, than we will have to check (and replace) the optical transmitter in the AD-box and the optical receiver in the USB-receiver (the decreased output on the transmitter is the most likely cause). Please sent the AD-box, optic fiber and USB-receiver to us for services.

One further point: are you testing with or without extra Analog Input Box (AIB) ?

Best regards, Coen (BioSemi)

[alexander9]

Hi,
Thanks for getting back to me.

Yes, there are a lot of spikes in the EEG together with these spurious triggers

I can try compressed air, however, I do not have another optical fibre cable to try. As the problem only is apparent after 85 min it will take some time to try out. I can run a script with triggers for that long but not with the electrodes connected. So, if spurious triggers do not appear after 85 min, I will not know for certain whether they will appear next time I test a participant and everything is connected.

If I send the equipment back to you, when could you return it? Time (as always) is of its essence here!

If easier you can call me on Tel: +44 (0)208 411 6328
bw
alex

[alexander9]

HI
I'll ship it back hopefully today, is there any name I should put on the box other than the following

BioSemi B. V.
WG-Plein 129
1054SC Amsterdam
Netherlands


bw
alex

[Coen]

The above is fully OK, best regards, Coen (BioSemi)

[Coen]

We let your system run through the weekend, but the ActiView software could not detect a single spurious trigger on any of the 16 lines during the full 250,000 seconds. We are therefore quite sure that this is not an error caused by the hardware or ActiView acquisition software.

Please use the file cropper tool (http://www.biosemi.com/download/ToolsFo ... pper86.zip) to isolate a smal section of BDF file were the problem starts (e.g. select to extract a file starting at 5000 seconds, and ending at 6000 seconds). Test whether you see the spurious triggers also in this new smaller file. If no, then the problem is surely caused by your review software (what are you using ?).

Best regards, Coen (BioSemi)

[alexander9]

Thanks for your support. I does seem as though the issue is with the analysis software, or some hardware-software compatability issue. I use Brain vision Analyzer 2 for my analysis. Brain Products are currently looking into the problem and the issue apparently persists when opening the file in EEG lab as well, but not in CARTOOL. Potentially the issue is with the high sampling rate and the length of the recording. The additional markers are added after 85 min of recording.

So, it is not clear what the issue is but if the data is cropped and split into two, then the markers disappear. If the data is then merged then the file is ok.

Thanks again for being quick in testing the equipment and sending it back to me

bw,
Alexander Jones
Middlesex University London