negative onsetdelay& log with prerelease

[Karl]

Hello, all

We just got a new laptop (win7) and installed the eprime
(professional2.0). Our fmri paradigm is relatively simple--every trial
has two components: 1) a fixation period with duration varying from
2000 to 4000ms 2) a pic presentation for 2000ms during which a
response of button pressing is collected.

1) We tried to prerelease the pic, but whatever the prerelease number
is, there are still lots of non-zeros in the pic-onsetdelay log file.
They are generally less than 20ms, but more concerning is that there
is even negative onset delay, like -5 or -11. What could the problem
be?

2) if we set the pre-release too long, it seems to disrupt logging the
response we collect during pic presentation. For our case, should we
use prelease of pic or not? If not, how can we still ensure pic onset
is accurate? Chapter 3 is quite unclear about this.

3) It is suggested here to use cumulative timing code for fMRI. Just
curious about shorting the stimulus presentation duration is less
concerning in fMRI?

Thanks in advance

Karl

-- 
You received this message because you are subscribed to the Google Groups "E-Prime" group.
To post to this group, send email to e-prime at googlegroups.com.
To unsubscribe from this group, send email to e-prime+unsubscribe at googlegroups.com.
For more options, visit this group at http://groups.google.com/group/e-prime?hl=en.