Find out exact runtime/duration of a given experiment

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Adam Schadler

Jul 1, 2021, 1:00:32 PMJul 1
to E-Prime


I have recently modified an E-Prime fMRI experiment by adding a few extra trials. I will need to add a few extra TRs to my fMRI protocol.

Is there a way to know the exact runtime of an experiment? That is, from onset of first to termination of last stimulus.

I have timing files outputted that give onset times for each stimulus event, but I wanted to see if there was a potentially more accurate way to find out experiment runtime/duration.

Thank you so much for your help!

Adam Schadler

David McFarlane

Jul 1, 2021, 2:34:13 PMJul 1

I always start out by just doing the arithmetic based upon object
Durations. But this works only if you use Cumulative (instead of Event)
timing mode throughout. I also like to log the TargetOnsetTime of the
first object of the scan and the TargetOnsetTime of the first object
following the scan in order to verify the scheduled timing of each run
(note that TargetOnsetTime indicates the *intended* or *scheduled* onset
time as opposed to the achieved onset time, which is all that you can
actually control). Then I can just do test runs and see how the timing
works out -- when programmed properly, the *scheduled* runtime for the
scan comes out *exactly* the same for each run, down to the millisecond.
I can even do this with speeded up test runs, using either E-Run Test
or by messing with Clock.Scale. Remember, fMRI run timing should not
depend upon subject responses, which makes it very easy to do these test
runs. (I include an exercise about fMRI timing in my online E-Prime 2

- David McFarlane
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