losing ERP triggers in E-Prime

[Tony Zuccolotto]

Richard,

Depending on how your trial presentation sequence is designed this could
be a side effect of using PreRelease, e.g. if the triggers you are
missing are perhaps related to responses then it could be a situation
similar to the following...

Say you have a display & response duration of 2000ms with a PreRelease
of 200ms on the stimulus presentation object.   At time 1800 the object
collecting the response actually stops executing its .Run method
(2000-200 = 1800), and moves on to the next object (or Inline script)
that follows.   If your trigger is sent from an Inline directly after
the object, and that script is designed to only send a trigger when
there is a response accepted then you have a 10% chance of a trigger
being ignored/skipped (e.g. 200/2000 = 10%).  Specifically you are at
risk of skipping a response (which is yet to be made) if the subject
response comes in anywhere between time 1800 and 2000 (i.e. after your
script to send the trigger has already executed).

If you think something like this is happening you should either: not use
PreRelease on this object (which may cause other issues to deal with
depending on the nature of your experiment), or examine the
<object>.InputMasks(1).IsPending property to assure that the response
input has completed before examining other properties and sending your
trigger.

Please reply back to the list when you get this issue resolved, i.e.
triggering via WritePort has been very reliable so if this doesn't turn
out to be an experiment specific (or possibly hardware specific) problem
PST would like to know about it and/or try to replicate it to get the
specific problem identified and resolved.

Thanks,
Tony

*** DISCLAIMER: ALL VIEWS EXPRESSED ARE MY OWN AND DO NOT NECESSARILY
REFLECT THOSE OF PSYCHOLOGY SOFTWARE TOOLS ***
Anthony P. Zuccolotto
Vice President
Psychology Software Tools, Inc.
2050 Ardmore Boulevard
Suite 200
Pittsburgh, PA 15221-4610
Phone     412-271-5040
FAX       412-271-7077
Email     anthony.zuccolotto at pstnet.com
Internet  http://www.pstnet.com



> -----Original Message-----
> From: Don.Rojas at UCHSC.edu [mailto:Don.Rojas at UCHSC.edu]
> Sent: Wednesday, November 12, 2003 1:56 PM
> To: eprime at mail.talkbank.org
> Subject: RE: losing ERP triggers in E-Prime
> 
> It would be helpful if you could tell us what the sampling rate,
> stimulus rate, trigger duration are for your experiment.  Also, are
> collecting data in continuous mode or epoch mode?  Finally, how are
you
> actually triggering using Eprime?  Are you using the Writeport command
> in an inline script or are you OnsetSignalEnabled property of the
> stimulus object?
> 
> Donald C. Rojas, Ph.D.
> Assistant Professor of Psychiatry
> University of Colorado Health Sciences Center
> Neuromagnetic Imaging Center
> Box C268-68 CPH
> 4200 E. 9th Avenue
> Denver, CO 80262
> (303) 315-8624 (ph)
> (303) 315-5395 (FAX)
> 
> 
> -----Original Message-----
> From: eprime at mail.talkbank.org [mailto:eprime at mail.talkbank.org] On
> Behalf Of Richard P. Heitz
> Sent: Tuesday, November 11, 2003 7:33 PM
> To: E-Prime Listserv
> Subject: losing ERP triggers in E-Prime
> 
> Hello,
>     I am running E-Prime with a NeuroScan EEG.  I am having an odd
> problem -
> it is randomly losing triggers (data markers sent through the parallel
> port).  The loss it absolutely not systematic, and I lose
approximately
> 7%
> of all my data marks.  I do not lose triggers with a different program
> (Presentation), nor do I lose triggers using E-Prime with an eye
> tracking
> unit.  If anyone has had this problem, or has the same setup, I would
> appreciate some help.
>
------------------------------------------------------------------------
> ----
> ----------
> Richard P. Heitz, M.S.
> Attention and Working Memory Lab
> Georgia Institute of Technology, Atlanta Georgia 30332
> Email: gte016z at prism.gatech.edu
> Office: 350 J.S. Coon Building
> Web: http://psychology.gatech.edu/renglelab
> 
> 
>