AW: trigger TMS + collect responses during stimulus presentation

[Paul Gr]

Hello Bianca,
 
When the display duration is set to zero, you can immediately continue with a script to generate one or more TMS pulses. The target stimulus will stay on screen when the user script is executed, unless you use the ClearAfter property. The advantage of this is that the pulse timing becomes independent of the refresh cycle of the monitor. In the example script I also used the OnsetSignal properties to generate the first trigger at the exact onset of the stimulus. (I hope this example was included in my previous email.) 
 
However, instead of setting the duration (and prerelease) to zero, it is also possible to set the duration to the requested value (say 200 ms) and use exactly the same value as PreRelease time to allow your script to execute immediately after stimulus onset. This way EPrime correctly schedules the start time of mask object at stimulus onset + 200. If you use a duration of zero instead, EPrime expects the mask to start immediately after the target and considers the time taken to execute the user script (for the trigger pulses) as unexpected delays. I think I accidentally mixed those two constructions in the text of my previous email. (Sorry for the confusion.)
 
The same technique can be used for the Mask image.
 
best,paul


From: bianca.de-haan at klinikum.uni-tuebingen.deTo: pauls_postbus at hotmail.com; eprime at mail.talkbank.orgSubject: AW: trigger TMS + collect responses during stimulus presentationDate: Tue, 19 Jun 2007 17:32:29 +0200






Dear Paul,
 
Many thanks for your answer and excellent advice, it definitely did go a long way towards solving my problems. However, inevitably, I still have a problem left.
 





<snip>  There are several good arguments for not placing the mainstimulus preparation and execution inside the first loop. The prefered way would be to run the mainstimulus object just before the loop. Then use a simplified loop to generate the trigger pulses that should be generated during the target. Also use the sleep() instruction inside the loop to specify the delays for each iteration. You should also place the OnsetSignal initialisation script somewhere before mainstimulus.run. Also set the duration and prerelease vaules of mainstimulus to the required duration of the target.[emphasis added] This will prevent large timing error values for the following objects.
<snip>
I do not quite understand this part of your advice. I want to be able to present TMS pulses during presentation of the mainstimulus as well (so some pulses will occur during the mainstimulus with the first pulse synchronised at mainstimulus onset and some pulses will occur during the subsequent response-collecting mainmask2. Mainly the part where you advice me to set the duration of the mainstimulus to unequal 0 therefore puzzles me. When I follow that advice, E-prime will not execute the TMS-pulses until the mainstimulus duration has elapsed. 
 
I ask since I have now still set the duration of the mainstimulus to 0 followed by a TMS-generating loop (akin to the 1 you adviced me to use for mainmask2) where the TMS-pulses are generated and that terminates when the target duration has reached. This works, however, as you predict, I find timing errors for the onset of the mainmask2 and the TMS pulses that occur during the mainmask2.
 
Is there any way to generate pulses during presentation of mainstimulus without creating timing errors for the following objects?
 
I would be very grateful if you could help me tie up this final loose string,
 
Bianca de Haan
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