Ahh, actually I didn't realize that Acrobat has this feature. That should be sufficient, and you can always have a look which volume the scanner was recording at the transition of the epochs.
What we often do with visual paradigms is to present videos and we have successfully used the audio out to trigger the scanner externally. That's an easy way to achieve temporal synchronization. Videos can be displayed using matlab and cogent, and that is accurate up to about 1ms on our system, so that is entirely sufficient. You can get the requirements for external trigger pulses from your scanner handbook. Also a bit of a ghetto-tech approach but very efficient. However, the vendors don't really like it (i.e. to drive their scanner by a video;)
-----Ursprüngliche Nachricht-----
Von: FSL - FMRIB's Software Library im Auftrag von Andrew Janke
Gesendet: Mi 18.02.2009 23:28
An: [log in to unmask]
Betreff: Re: [FSL] AW: [FSL] AW: [FSL] "standardised" fMRI tasks.
> I'd be curious and happy to have a look!
Thanks, I will put a few of them up.
> I like the idea to use PDFs for display. How do you synchronize it temporally with the scanner? Usually, you don't need to be fancy about it: being precise to 1 TR is quite sufficient for a block design.
The initial synch is done in a "Biological" fashion. ie: press
PageDown/LeftArrow when the scanner reaches steady state and starts
it's bit of counting. Yes this could be done with a TTL pulse^ but I
am going to Ghetto-tech. (ie: $0 fMRI, well ok it cost me $30AUS
rupees to make a screen from Electrical conduit, ball point pen
shafts, string and cheap polyester).
The Auto Advance is a feature in PDF ala this:
http://www.creativetechs.com/iq/build_an_acrobat_pdf_slideshow.html
I just set it to auto advance every "x" seconds and put in repeats of
images if required. Currently I am making the pdf's in OpenOffice so
that again is $0.
The Projection is done with a cheap Projector in a rear-projection
setup. Rather than buying a (more expensive) projector that can flip
the image I am just using a mirror to flip the image in the console
room. Seems to work fine.
a
^ full TTL synch should not be a problem all I would have to do is set
the Pulse to map to PageDown and all would be hunky-dory. Still at
this stage it is just one more thing to go wrong.
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