Eprime triggers to EEG out of sync

[David McFarlane]

Ryan,

Just a few remarks ...

"Apparently e-prime is limited to sending out 250 labels ..." -- Not 
clear if you think that E-Prime may only do signal output events 250 
times during a session, or if you think that it may use only 250 
different signal values, so to clarify:  (1) E-Prime may do any 
number of signal output events during a session.  (2) Typically, you 
output an 8-bit value.  Unsigned 8-bit values may range from decimal 
0 to 255.  You would reserve 0 for an "off" or null value, thus, 
ordinarily, E-Prime is "limited" to using 255 unique signal values 
(unless you can coax E-Prime into outputting 16-bit signals, in which 
case it will use 65,535 unique signal values).  Not sure why you 
would need a unique signal value for each event during a session 
anyway, typically you reuse signal values on different trials just to 
signify general categorical information (stimulus onset, etc.).

Post-hoc labelling -- If you can output one signal at a known time 
relative to stimulus onset, and if all your later markers come at 
known offsets from that, then it should be straightforward to send 
the first marker at run time (which you already know how to do in 
E-Prime), and add the remaining markers later during analysis.  Sure, 
it might be slick to have E-Prime do all this at run time, but I 
don't think it is worth the trouble.

As far as getting E-Prime 1 to do this at run time anyway, these 
threads may be of some interest (even though they refer to outputting 
signals relative to the time of response instead):

https://groups.google.com/d/topic/e-prime/z8PQMH1cf70
https://groups.google.com/d/topic/e-prime/7w5ajYuHqgw

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

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At 8/30/2014 05:05 PM Saturday, Ryan Blything wrote:
>I came across this post because I am going to be trying a similar 
>thing in my experiment such that we will be using e-prime v.1 to 
>present audio stimuli and we are interested in setting markers so 
>that they are not just at the onset of stimuli - but also at a 
>number of specific points in each sentence (e.g. onset of the verb, 
>noun, preposition). This would require having several markers for 
>each trial and Im wondering about the best way to go about this? One 
>way is through code but no one seems to have managed to do this 
>successfully that Im aware of. How did it go for any of you? Im 
>quite new to e-prime and SPM (which we will use to analyse data) so 
>I would appreciate any advice before I continue.
>
>An alternative option Ive heard about is post-hoc labelling, which 
>would be done in SPM, post-hoc working from the onset triggers 
>provided by e-prime (and psuedo-marking points later in the 
>sentence). Im not very familiar with SPM but am I right in thinking 
>that as long as the onset of the sentence is marked accurately, then 
>we can - post hoc - set markers anywhere we want in the data 
>thereafter? This may be the most ideal solution because I have 200 
>sentences, each of which must be labelled separately (so that I can 
>recognise each one). Apparently e-prime is limited to sending out 
>250 labels so perhaps post-hoc multiple labelling is the answer. I 
>would appreciate any thoughts any of you may have.
>
>Many Thanks,
>Ryan

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