[Eeglablist] double event markers from Biosemi .bdf files

[Jeff Johnson]

We frequently have this problem too, and we figure that it has something to 
do with either pausing/unpausing or clicking the mouse in Biosemi's 
acquisition program (in Labview). One way around it (although we haven't 
tried) might be to pause/unpause the acquisition by sending a byte (244 or 
245?) from your stimulus computer, instead of using the mouse.

To get around it in EEGLAB, we usually just epoch our data around the 
events that have a particular value. For example:

pop_epoch( EEG, {'[1621761]'}, [-0.100 2.000] );

Our events of interest always have a value of 1621761, whereas the 
extraneous events have different values. You can easily find your event 
values by using the pull-down menu in EEGLAB (edit >> event values, I 
think). As you note, there are probably many other ways around this 
problem, but this method works about 99% of the time for us.

Jeff

At 09:14 PM 2/14/2005 -0700, Jim Kroger wrote:
>Hello, I am wondering if anybody else has experienced this problem. We use 
>a Biosemi 128-channel.
>Channel 129 has event markers.
>
>When using this channel to mark event times in EEGLAB, we have some kind 
>of ring or artifact that causes EEGLAB to mark two events instead of one. 
>We also try loading this into EMSE, and do not have the problem.
>
>We're having a bit of trouble understanding why this happens. Although we 
>can imagine ways to program around the problem, it would be best if we 
>understood it.
>
>Many thanks for any pointers.
>
>Jim
>
>
>
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