Losing ERP triggers with E-Prime

[Richard P. Heitz]

That makes sense, but unfortunately, I am not using pre-release, nor is the
response period any where near the display stimuli (temporally, that is).
To further explore the problem, I wrote a simple program in E-Prime using
the writeport command and an identical program in Presentation.
Presentation lost no triggers whereas E-Prime lost 7%, again randomly.  So,
I figure it has to be something about the way E-Prime is writing to the
parallel port.  Is my earlier speculation about a "pulse width" even viable?



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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


 Original Message -----



  X-Sieve: CMU Sieve 2.2
  Subject: RE: losing ERP triggers in E-Prime
  Date: Thu, 13 Nov 2003 08:52:14 -0500
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  Thread-Topic: losing ERP triggers in E-Prime
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  From: "Tony Zuccolotto" <anthony.zuccolotto at pstnet.com>
  To: <eprime at mail.talkbank.org>
  Sender: <eprime at mail.talkbank.org>
  X-LR-SENT-TO: prism.gatech.edu

  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.
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  > -----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.
  >