[Eeglablist] biosig function and bio-semi triggers - mystery resolved!

[Arnaud Delorme]

Dear Baris and others,

EEGLAB 10 contains the latest version of BIOSIG and uses BIOSIG's defaults for extracting event information.
Would you mind making sure that your files are imported as expected using this version?

Best regards,

Arno

On Apr 26, 2011, at 2:20 AM, Alois Schloegl wrote:

> 
> Some time ago, based on user feedback, I've already set the default 
> decoding method in biosig/t200/bdf2biosig_events.m also to
>    case 4 (rising edge, of lower 15 bits)
> Also for Baris, this mode is working fine.
> 
> Therefore, I suggest that the default decoding method in eeglab should 
> be also changed to this method, and as used in biosig.
> 
> 
> Kind regards,
>    Alois Schloegl
> 
> 
> 
> 
> On 04/20/11 13:26, Baris Demiral wrote:
>> Hi everyone,
>> 
>> I would like to comment on the previous discussion about the biogig import
>> of the bdf files, related to the warnings to some triggers. Some of you
>> previously reported that you see
>> the following error messages after importing bdf files with biosig function:
>> Warning SOPEN: number of event onset (TYP=0) and event offset (TYP=8000)
>> differ (371,366)
>> Warning SOPEN: number of event onset (TYP=5A) and event offset (TYP=805A)
>> differ (276,280)
>> Warning SOPEN: number of event onset (TYP=5B) and event offset (TYP=805B)
>> differ (85,88)
>> 
>> I recognized that this is due to the "response" triggers. Biosig
>> successfully detects triggers of Stimulus type (first 8 bits of the Status
>> channel) but it is not capable of
>> detecting the last 8 bits of the Status channel reserved for Response coming
>> mainly from the Switch-boxes.
>> 
>> That might be the reason why Arno and some other could not replicate this
>> bug, probably because they did not use Biosemi response switch (?). What
>> happens is that biosig somehow detects the Response trigger, but then it
>> marks them as "0s". I know that BioSemi marks the off-set of the response
>> switch (release) and puts "0".
>> 
>> Another reason for the warning might be that when you use response boxes, as
>> well as recording, say, accuracy by looking at the response, and send
>> triggers to eeg machine before the button release, they may add up and give
>> you weird trigger codes. But, the codes are not arbitrary and can be easily
>> converted.
>> 
>> Any comments? Anyone responsible for the Biosig function, could you reply
>> please?
>> 
>> Best,
>> Baris
>> 
>> 
>> 
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