Stimuli/ Triggers/ Timing difficulties

[David McFarlane]

Sorry, I forgot to elaborate on the "finesse" part.  The shortcoming 
of this solution is that you *must* remember to adjust the PreRelease 
value any time that you change Duration, and it is *very* easy for 
most users to overlook that, as I can tell you from experience!

-- David McFarlane


At 4/19/2012 02:09 PM Thursday, you wrote:
>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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