E-prime does not recognise fMRI scanner trigger pulse

Tue May 13 18:20:59 UTC 2014

Christina,

First, I would put an oscilloscope on the trigger output of your 
scanner and verify that it works as expected -- Does it produce valid 
TTL levels?  Does it produce a pulse for every slice, or every volume 
scan?  How long does each pulse last?  What shape does each pulse take?

Next, you might want to get a bit of general background on how a 
parallel port works.  You may start at 
http://en.wikipedia.org/wiki/Parallel_port , and go from there.

Indeed, as see from that article, pin 10 is used for ACKnowledge.  I 
have never heard of any software using that pin for input, but you 
learn something new all the time!  That probably goes back to the 
days when parallel port data served as output only (back then I used 
the control port pins myself for input), but we now have 
bidirectional data through pins 2-9, and E-Prime (quite rationally 
IMO) uses that.

Next, I have never used EEfMRI, but if RunBegin uses {^} as the 
trigger value by default, then I suspect that RunBegin takes its 
input from a Keyboard Device, *not* the parallel port -- in 
particular, {^} does not seem like a valid input from the parallel 
port, unless you meant it as a mask (i.e., ASCII value 0x5E, see 
http://www.asciitable.com/ ), but that would be just weird.  By 
comparison, around here we use a PST Button Response System (BRS) for 
subject input with fMRI, that acts like an SRBox connected to the 
serial port of our E-Prime PC (with scanner trigger plugged into the 
BRS), in E-Prime we map the SRBox Device to the Keyboard Device 
(along with some other configuration), then we just use any E-Prime 
input object (typically, a TextDisplay) with Allowable set to {^}, 
which, indeed, happens to be the default value that the BRS presents 
*as if it were a keyboard* upon any trigger pulsed (I actually 
discuss this fully in a lesson in my online E-Prime course).  Works just fine.

Next, I would set aside your full fMRI experiment program and start 
making one or more small test programs just to test getting trigger 
input from your scanner.  E.g., a program with nothing more than a 
List with a Procedure with a TextDisplay that shows a prompt and 
waits for inputs from several devices, followed by a TextDisplay that 
shows whatever input the first TextDisplay got, etc.  There is some 
chance that your inconsistent trigger problem comes from some 
peculiarity of your fMRI experiment program, the test programs should 
help to debug that.

Finally, if you still get inconsistent results from your trigger 
input, I would put an oscilloscope on the parallel port pins while 
your test program runs with your fMRI triggers, and make sure that 
you get good trigger pulses under those conditions.

That all said, as it turns out just now I have my own problems 
getting input from parallel ports using EP2.0.10.353, and I am 
working on this with PST support myself!  In this case, I have three 
PCs -- With one of them EP2.0.10.353 manages to use the parallel port 
for both input & output just fine; with another, output works, but 
not input; and with the third, I get an "Address Invalid" error as 
the program starts.  Oh well.  This may have something to do with the 
peculiarities of these three systems.  Luckily, in this case we can 
always revert to an SRBox.

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

/----
Stock reminder:  1) I do not work for PST.  2) PST's trained staff 
take any and all questions at https://support.pstnet.com , and they 
strive to respond to all requests in 24-48 hours, so make full use of 
it.  3) In addition, PST offers several instructional videos on their 
YouTube channel (http://www.youtube.com/user/PSTNET ).  4) If you do 
get an answer from PST staff, please extend the courtesy of posting 
their reply back here for the sake of others.
\----

At 5/13/2014 12:42 PM Tuesday, andreou.christina at gmail.com wrote:
>does anyone here use E-Prime for fMRI experiments? We are trying to 
>get it to work and even got the EEfMRI Extension, but the RunBegin 
>Package Call simply refuses to recognise the trigger pulse. I tried 
>simply inserting a wait object and define the parallel port as 
>trigger mask (allowable response {ANY}), and it didn't work either.
>We did a bit of troubleshooting, and ended up changing the cable 
>connecting the scanner to the PC: the cable we normally use 
>transmits the signal to pin Nr. 10 of the port (acknowledge or 
>interrupt pin), if I understood our technician correctly - this 
>works both with Presentation and Cogent software. However, we saw 
>something on the pstnet support page about E-prime recognising input 
>to pins 2 to 9, so we changed that and used a cable that sends the 
>signal to pin Nr. 9. Now we have a very peculiar situation:
>
>- the trigger pulse is recognised by the wait object, but only 
>sometimes (every 4th, 5th, or 10th pulse is recognised, there does 
>not appear to be a system). When it is registered, it appears as 7 
>in the E-Dataaid File and in the .pdat file.
>- when I substitute the default allowable input (^) to the RunBegin 
>Package Call to 7, it still isn't recognised at all.
>
>I am in contact with pstnet support, but we haven't come further than that.
>
>Has anybody encountered similar problems when setting up fMRI 
>experiments? Any input about your experience and/or settings you 
>came up with will be valuable!
>
>Thanks,
>Christina

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