Massimo-
I use E-Prime in my student labs. It is a good teaching tool. However, I
would offer extreme caution in using this software for research. There are
several things you should consider:
1.) Stimulus timing may not be precise. Using an oscilloscope, we found
that E-Prime could not present stimuli faster than 3 frames.
2.) Left to it's own devices, E-Prime will always lose a bit of time per
trial. If you request it to wait 300 ms, it will wait AT LEAST 300ms, but
sometimes it will be considerably longer. The data log will record these
errors. I found that for a series of trials that were supposed to take 12
sec, the actual time varied between 12.1 and 13.5 seconds (+10%). This
would be a huge problem with block designs, and one that would at least
need to be considered with for event-related designs. It may be possible to
write some inline code that will help resynchronise the timing (e.g. at the
end of each trial, wait until a certain time has elapsed), but if you
simply add a standard E-Prime wait, it will not correct for previous delays
- it always waits for AT LEAST the time you specified.
All this was done ove the summer - PST may have improved things with the
latest beta release. However, before using this software with any
experiment, I strongly advise you to carefully look at the timing issues.
-chris
At 10:39 30/10/2001 +0100, Massimo Danna wrote:
>Dear colleagues working with SPM,
>
>Our names are Massimo Danna and Pasquale Gagliano. We are two engineers of
>the group of San Raffaele Hospital in Milan who like neuro researches. We
>work with Ing Paola Scifo.
>Here we are using a 5.7 Signa GE 1.5 Tesla Scanner for functional Magnetic
>Resonance and we want to realaze event-related protocols so we need a
>exact synchronization between tomograph and PC/MAC. Sorry but we did
>find any e-mail about this in the email list so we have some question
>about it:
>
>1. Which kind of system is there to realize event-related protocol?
>
>We have thought to buy 2 cards I/O (PCI-1200 National Insruments and
>SC-2071 National Insruments plus an exernal home-device containing a
>flip-flop D:
>2. Are these cards good or not?
>3. Do somebody know if this kind of cards are useful and with which
>software of stimuli?
>
>Moreover we have thought to buy E-Prime:
>4. Is this software good or not?
>5. Are these cards compatible with E-Prime?
>
>Sorry to trouble you but this is the first time that we use GE Scanner
>interfaced with a PC/MAC for event-related protocol.
>Thank you very much in advance for any help.
>
>Massimo and Pasquale
__________________________________________
Dr. Chris Rorden
Department of Psychology
University of Nottingham
Nottingham NG7 2RD, UK
Tel: +44 [0]115-951-5294
Fax: +44 [0]115-951-5324
http://www.psychology.nottingham.ac.uk/staff/cr1/
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