Stimuli/ Triggers/ Timing difficulties

[David McFarlane]

We do this all the time for our EEG programs, but it requires a 
little finesse.  In short, we use a PreRelease value of 1-20 ms less 
than the Duration of the stimulus object.  E.g., for your object with 
a Duration of 500, set PreRelease to 490.  Now your trigger will 
coincide exactly with the onset of your stimulus, and will last for 
10 ms, when the "offset" of the stimulus occurs.

Note that, in E-Prime parlance, stimulus "offset" does not mean 
either the end of stimulus presentation, nor the onset of the 
following stimulus; "offset" actually refers to when E-Prime stops 
executing code for that object and moves on to executing further 
instructions.  Someday I need to write this all up, but it's tricky 
to describe this all correctly.

-----
David McFarlane
E-Prime training 
online:  http://psychology.msu.edu/Workshops_Courses/eprime.aspx
Twitter:  @EPrimeMaster (twitter.com/EPrimeMaster)


At 4/19/2012 01:44 PM Thursday, you wrote:
>Hello E-Prime experts,
>
>We are Working in our lab with Iwave and E-prime;
>
>There's a problem that bothers us.
>
>The triggers stay for 500 msec, exactly the same duration as the
>Stimuli. We want to write a code that makes the trigger and stimulus
>onset at the same time exactly( which is the case now with the new
>line: Stimulus.OnsetSignalData = c.getattrib(`"Cond") ) AND the
>trigger to offset as quickly as possible while the stimulus stays on
>the screen for 500 msec.
>
>Looking forward to any solutions
>
>Many thanks in advance.

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