[Eeglablist] EEGLab, BioSemi ActiveTwo mk2 and event markers

[Lloyd Smith]

Hi, Erin.  I am replying to the EEGLAB list, too, so that others are
aware of the situation.  The problem with EEGLAB not reading event codes
was related to the way the version of EEGLAB I was using at the time
read the event channel.  I believe it affected only data files created
with mk2 ActiveTwo systems.  I am not sure if it was fixed in a later
release version of EEGLAB.  The mk1 / mk2 state of the ActiveTwo system
is encoded in the most significant bit of the most significant byte of
the status channel.  In two's complement notation, this results in a
negative number.   The version of EEGLAB I was using at the time assumed
that the Status channel should always contain positive numbers, so it
ignored all of the events, given that they were all encoded as negative
numbers.  One work around would be to ignore the event channel on
loading data and use the menu functions to decode the events in the
Status channel after the data have been loaded.  I seem to recall that
this did resolve the problem for us in December, although I am not sure
if we had to download some new BioSig code to make that work.  I must
refer you to the EEGLAB list for more specific suggestions.
 

Lloyd Smith
Owner
Cortech Solutions, LLC

321 N. Front Street, Suite 113
Wilmington, NC 28401 USA
Office: 910-362-1143
Mobile: 910-431-2811
Fax: 910-362-1147
E-mail: LSmith at cortechsolutions.com
Web: www.cortechsolutions.com



 


________________________________

	From: Erin McMullen Jonaitis [mailto:mcturtle at gmail.com] 
	Sent: Thursday, August 24, 2006 3:15 PM
	To: Lloyd Smith
	Subject: EEGLab, BioSemi, and event markers
	
	
	Hi!
	
	I'm a graduate student having a problem with EEGLab.  I looked
through the EEGLab mailing list archives and saw that you had a very
similar problem last December, but did not see a solution posted.
Basically, the software isn't recognizing the event channel in my intact
datafiles that read fine in BESA.  Were you ever able to solve the
problem?  If so, would you mind giving me some pointers?
	
	Thanks very much in advance.
	
	Erin McMullen Jonaitis
	

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